Proceedings of the 63rd Conference of Metallurgists, COM 2024

Fatigue damage mechanisms in hydraulic turbine steels are complex and depend on their underlying microstructure. Unfortunately, the methodology used for designing today’s turbines does not consider micro-mechanisms responsible for their fatigue damage. To circumvent this limitation, ongoing efforts at Hydro Quebec aim to develop Integrated Computational Materials Engineering (ICME) tools for the future development of hydraulic turbine digital twins that incorporate microstructural effects. In the context of the company’s aging assets and the need for increased production of clean energy, there is indeed a great need for better decision-making with respect to the fabrication, use, and repair of hydraulic turbines. This document showcases ongoing initiatives at Hydro Quebec toward the development of an ICME framework for hydraulic turbine engineering.

In this study, digital light processing (DLP) was employed to 3D print ceramics based on alumina (Al2O3) for evaluating their reciprocating wear behavior. The investigation focused on the influence of different surface orientations with respect to the build plate, each with a constant layer thickness of 25 μm. The effects of layer thickness were studied on the worst performing sample. Sintered Al2O3 components underwent wear tests perpendicular to the individual layers. Wear tests, conducted with a β-Si3N4 counter face sphere under loads of 40 and 60 N, revealed that samples with the intermediate build angle demonstrated the lowest coefficient of friction. Microstructural analysis disclosed cracking/spalling damage and the formation of a tribolayer in 3D-printed ceramic samples. Further findings from this research highlight the crucial design considerations when utilizing additive manufacturing (AM) technologies for producing ceramic wear components, offering valuable insights into optimizing wear performance.

The scientific interest towards additive manufacturing (e.g., 3D-printing) of high-entropy alloys is rapidly growing due to its higher flexibility for design and operation. The fabrication of CrMnFeCoNi (or Cantor) high-entropy alloy via additive manufacturing not only overcomes the challenges of casting and powder metallurgy but also alters the deformation pathways due to significant microstructural changes. Thus, the compressive deformation behavior of CrMnFeCoNi high-entropy alloy manufactured via laser-beam powder bead fusion was analyzed in the current work using electron backscatter diffraction (EBSD). The simultaneous activation of different deformation mechanisms was scrutinized, wherein the formation of dense slip traces was observed along with the activation of deformation twinning.

Certain nickel polyalloys, such as Ni-P-h-BN and Ni-P-PTFE, are commonly used in the molding and stamping industries as they produce superior anti-galling coatings. In addition, PTFE and hexagonal boron nitride (h-BN) are known for their high thermal stability and great solid lubrication, which can improve the wear characteristics of the coating. h-BN particles also improve the corrosion resistance of nickel-phosphorus (Ni-P) coatings, and heat treatment can raise their hardness. Due to the nature of the previously mentioned operations, these coatings may develop defects over time, exposing the base substrate. This study focuses on the corrosion behavior of h-BN co-deposited on Ni-P coating by utilizing an electroless deposition process. Electrochemical impedance spectroscopy (EIS), a widely used approach to analyze the anti-corrosion performance of protective coatings, is utilized to study the interaction between the coating and aluminum substrates of mold used in the tire industry. The h-BN is known for its high thermal stability and great solid lubrication, especially in industry, which can improve the wear characteristics of the coating. On the other hand, poor wettability of the h-BN coating counts as a disadvantage that can be solved by incorporation within the matrix layer of an active metal such as nickel. The results revealed that h-BN particles improved the corrosion resistance of the Ni-P coating, and that heat treatment can increase the hardness of the coating.

Ceramic materials, renowned for their mechanical strength and environmental stability, face challenges in structural applications due to inherent brittleness and low damage tolerance. Polymer-derived ceramics offer a solution by allowing near-net-shape manufacturing through polymer precursors, overcoming traditional processing limitations. Leveraging polymer additive manufacturing, specifically stereolithographic (SLA) 3D printing, provides versatility in creating complex shapes. We present the formulation of a commercial silicon oxycarbide (SPR 684) for SLA printing, involving the combination of preceramic polymer, a photoinitiator, crosslinkers, and additives. Pyrolysis transforms the printed polymer into a ceramic, comparable in density to conventionally processed samples. Despite quality issues such as porosity, the method is promising for crafting thin features and customized structures, making it ideal for low-cost SLA 3D printing of bioinspired, architected ceramic structures. Computed tomography imaging and compression experiments uncover the role of formulation components in crack initiation and propagation within the 3D-printed ceramics.

This study investigates the impact of incorporating sub-micron TiC particles on microstructural characteristics, and mechanical properties of laser powder bed fusion (LPBF)-fabricated CX stainless steel (SS) components. The findings revealed that TiC addition increased the density of as-printed parts compared to non-reinforced CX SS under similar processing conditions. Microstructural analysis revealed the formation of in-situ nano-sized TiC particles alongside initial submicron particles, with higher laser energy density resulting in a greater fraction of nano-sized TiC particles. Furthermore, the inclusion of TiC particles induced significant grain refinement and disruption of columnar structure. Notably, the introduction of 2 wt.% TiC showcased superior grain refinement and yielded the highest hardness.

Aluminium powder metallurgy (PM) is a near-net shape fabrication technology with a thriving market for various industrial niches. The basic sequence of manufacturing involved in the conventional PM process includes compaction, sintering, and secondary processing. It is known that most parts produced either through PM or other manufacturing technologies, depending on their engineering applications, are susceptible to fatigue cracking. Most notably, fatigue cracks often initiate from the surface of metallic components. Meanwhile, post-surface treatment processes such as shot and laser shock peening, which act to impose compressive surface stresses, are used to suppress and/or prevent the initiation of fatigue cracks for many metallic systems. While these surface modification technologies yield viable peening outcomes, there are operational costs and other drawbacks associated with them. For example, laser shock peening causes thermal damage to aluminium alloys and consequently affects the mechanical behaviour. It is envisaged that ultrasonic pulsed waterjet (UPWJ) peening, which offers a cleaner, safer, and more cost-effective approach compared to shot and laser shock peening counterparts, can be used as an alternate peening method to process aluminium alloys. Therefore, the objectives of this work are to assess the effects of UPWJ peening on the topographical, microstructural, and fatigue properties of an industrial PM aluminium alloy composite (with 5 wt.% AlN particles). The main finding from this work indicated gains in fatigue strength of up to 10% in the UPWJ peened aluminium alloy composite in comparison to the un-peened counterpart.

Due to the increased demand for high-quality metallic powders in additive manufacturing, the research and development of new reliable processes for their production is of great importance. In this context, ultrasonic atomization (UA) emerges as a possible method for producing metal powder. In this work, tin was ultrasonically atomized in an inert atmosphere producing spherical particles. The UA process was recorded, samples of the Sn-atomized powder were examined using SEM and FE-SEM, and sieve analysis was used to determine the cumulative mass size distribution.

Multi-principal element alloys (MPEAs) have recently received considerable attention due to their unique microstructural characteristics. These alloys have superior corrosion resistance and mechanical properties achievable through their complex compositions. In this study, based on two datasets, various machine learning (ML) methods were used to predict phases of MPEAs using statistical measures and the interactions of the features. The critical features, namely valence electron concentration, mixing enthalpy, mixing entropy, melting temperature, and electronegativity, demonstrated the greatest significance, yielding phase detection accuracies within 68.0–97.7%. Subsequently, we used a two-layered Bayesian shrinkage method for predicting mechanical properties, including microhardness, ultimate and yield strengths, elastic modulus, and elongation. This approach stacked the prediction power and model-based clustering of support vector machine regression, random forest regression, and a mixture of linear regression with experts. The Bayesian method we proposed surpasses the performance of conventional ML methods in predicting the mechanical properties of MPEAs. We then validated the models using experimental assessments.

Reliable joints are important for medical device fabrication. NiTi shape memory alloys and stainless steel are two examples. However, welding of these two alloys with fusion welding will result in the formation of intermetallic compounds. Here, two methods are used to study the formation of intermetallic compounds in the NiTi/SS joints. One is to control the melting location through beam offset in laser microwelding and another is to restrict the mixing through interlayer in resistance spot welding. The strength of the joint is evaluated.

Marine structures, including ships and offshore facilities, constantly face environmental challenges such as saltwater exposure, biofouling, and temperature fluctuations. Biofouling, the accumulation of aquatic organisms on these structures, elevates ship hull weight and roughness, resulting in high frictional resistance and increased fuel consumption. Moreover, it causes corrosion in metal structures, posing potential risks to marine equipment integrity and safety. The inadvertent release of biofouling organisms during cleaning or relocation of submerged structures further threatens human health, the aquatic environment, and socioeconomic values. Addressing this, the urgent development of eco-friendly coatings to prevent and manage biofouling is imperative. This research aims to pioneer anti-biofouling coatings through cold spray technology. Leveraging high-entropy alloys (HEA), these coatings will either inherently possess antifouling properties or serve as matrices for doped antifouling agents. Specifically, this study focuses on exploring cold spray of CoCrFeMnNi (cantor alloy) combined with varying copper weight ratios. The link that displays between process-structure-property-performance in these coatings will be explored and applied for materials and design. The outcome of the proposed research will make marine operations less energy-intensive, safer, and less costly, protect marine life, and will contribute to the blue economy.

Electroless nickel (EN) plating is a practical solution for coating underground buried pipelines, as it produces coatings with good corrosion and wear resistance, good adhesion, and uniform thickness. Owing to the versatility of the EN technique, co-depositing nanoparticles such as cobalt (Co) and polytetrafluorethylene (PTFE) can enhance the properties of the protective coating. Moreover, EN plating may be deposited in separate baths or combined, resulting in multilayered or composite coatings. Therefore, this work will focus on the systemization of the multilayered and composite electroless Ni-Co-P-PTFE coatings on mild steel, as well as the inspection of the post-heat treatment effect. Microstructural characterization is then examined using surface analysis techniques, namely X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and confocal laser scanning microscopy. The magnetic, scratch hardness, micro-hardness, and corrosion resistance properties of the multilayered and composite coatings are also compared.

Nickel Aluminum Bronze (NAB) alloys are strong, corrosion-resistant materials widely used in marine environments. NAB alloys processed via laser additive manufacturing (AM) techniques are starting to emerge in the literature and exhibit promising strength and corrosion properties. The high cooling rates found in AM can lead to microstructural refinement and better control of phase precipitation through subsequent heat treatments, leading to improvements in material performance. The ability to produce large, net-shape parts in an on-demand production scenario also makes directed energy deposition (DED) of these materials attractive in sectors such as marine defense, where NAB is used extensively. In the present work, DED of a UNS C63020 NAB powder was explored. Suitable deposition parameters that produced dense NAB specimen were identified and employed to fabricate solid test specimen. Post-heat treatment microstructures of laser clad specimen were evaluated using laser confocal microscopy and SEM-EDS, while X-ray diffraction was used to identify the constituent phases. The mechanical properties of the laser clad specimen were determined and compared to a laser powder bed fusion (LPBF)-processed NAB counterpart.

Electric arc furnace steelmaking has many environmental benefits compared to the blast furnace-basic oxygen furnace route but typically produces steel with higher nitrogen levels, presenting a particular challenge when aiming to produce interstitial free (IF) steel, which typically has a nitrogen content of <30 ppm. Whilst free nitrogen is known to have a deleterious effect on the formability of IF steel, the effect of higher levels of nitrogen combined in TiN precipitates is not clearly established. This work aims to investigate the impact of increasing nitrogen levels on the properties of IF steel. A route has been established for making lab-scale casts of IF steel with varying nitrogen contents and fixed excess Ti. The InTRAP technique has been used, in which smaller lab casts are inserted into a larger transfer bar before hot rolling, allowing processing parameters more representative of those at an industrial scale, and ensuring casts undergo the same heat treatment. Once processed, casts have been tensile tested and the microstructure analysed to investigate the impact of different nitrogen levels on properties such as formability. The casts show no clear deterioration in mechanical properties with increasing nitrogen content, which may be a result of the fast cooling rate, preventing the formation of large TiN precipitates. This may suggest that a high cooling rate, such as those on a thin slab caster, can minimise the impact of increasing nitrogen levels in IF steel, although it will be useful to compare results from casts with different cooling rates.

Martensitic precipitation hardenable stainless steels (PHSSs) are among the most studied materials for additive manufacturing (AM), but semi-austenitic PHSSs are much less explored. This work reports the AM of semi-austenitic PHSS 17-7PH samples using laser-powder bed fusion (L-PBF) and laser-directed energy deposition (L-DED) with different combinations of process parameters. The results show that for L-DED it was possible to obtain single tracks with good metallurgical bonding to the substrate and a nearly full austenitic microstructure. The samples manufactured by L-PBF with the optimal parameters showed densification above 99%, but with a predominantly ferritic matrix, which requires a solubilization heat treatment to archive the desired austenitic or martensitic microstructures.

High-pressure die casting (HPDC) is commonly used to produce large volumes of nonferrous components efficiently and inexpensively with complex and near-net shapes for a broad range of industries. The predominant failure mode of HPDC tooling and dies is thermal fatigue, leading to heat-checking or cracking. The thermal design and management in the die play a major role as it can be used to redistribute the stresses and reduce thermal gradients and thus improve the performance of the die and lifetime. Laser powder bed fusion (LPBF) is a 3D-printing technique that produces a component via a layer-by-layer process. Due to its nature, this technique allows the implementation of conformal cooling channels into tooling inserts, that is channels that are designed to be equidistant from the die surface thus helping in managing the thermal gradients and stresses that arise during the HPDC process. This work is a brief overview of how LPBF technology enables the die-casting industry to better control the thermal aspects of the die and ultimately produce better castings.

This study explores beta titanium alloys as advanced biomaterials addressing stress shielding challenges from stiff conventional metallic materials such as Co-Cr, Steels, and Ti-6Al-4V. Using laser powder bed fusion (LPBF) and in situ alloying of Ti and stainless steel powders, we fabricate a novel beta titanium alloy with a BCC phase and refined microstructure. The as-printed alloy exhibits low modulus (~87 GPa) and high strength comparable to commercial Ti-6Al-4V. Notably, the novel alloy demonstrates excellent biocompatibility, showcasing its potential for biomedical implants.

Mechanical architected metamaterials are a subset of structural composites that offer unique opportunities to expand the material properties space. Traditionally, cellular materials for industrial applications have been fabricated using conventional manufacturing processes such as casting, forming, and machining. To streamline processing times, these cellular structures are typically designed with periodic unit cells (i.e., lattices). While these lattices exhibit impressive stiffness-to-weight ratios, their periodic nature restricts architectural design flexibility and hampers advancements in properties such as fracture toughness and impact energy absorption. Our recent work explores the application of additive manufacturing fabrication techniques to produce intricate, heterogeneous, and aperiodic structures without incurring higher manufacturing costs. Through experiments and simulations, we have demonstrated that these heterogeneous cellular materials exhibit superior performance in applications that require high fracture toughness, strength, and energy absorption—for instance, for structural applications and bio-implant design. We will also discuss future research opportunities for these multifunctional materials to be used in a wide range of applications in the aerospace, automotive, sports, and biomedical sectors.

In response to the need for environmentally friendly materials and solutions, this study adopts a sustainable approach to developing Polylactic Acid (PLA): Carbon Nanotube (CNT) nanocomposite feedstock and filaments, by replacing hazardous solvents and petroleum-based polymers with eco-friendly alternatives. A green solvent-based phase inversion technique was employed to produce PLA:CNT feedstock with varying CNT concentrations compatible with material extrusion 3D printing. This process was followed by filament fabrication and 3D printing using a desktop fused deposition modeling (FDM) printer, with subsequent mechanical and electrical analyses. FDM printed sample with 5 wt% of CNTs showed a conductivity of 3.39 × 10−2 S.m−1. Electrochemical surface activation was done on 3D-printed samples to improve the electrical properties of the printed parts and enhance their performance in electrochemical sensing applications, by removing the PLA layer from the surface and exposing CNTs. The results in the detection of ferro/ferricyanide redox probes using the activated samples demonstrated the effectiveness of the proposed eco-friendly approach in developing 3D-printed advanced bio-nanocomposite for sensing applications.

The current study focuses on development of biomass filled polymer composite feedstock formulations for a low-cost desktop fused deposition modeling (FDM) 3D printer, using wood flour (WF), a by-product of the forest industry, and polylactic acid (PLA) as the matrix. A specific plasticizer has been incorporated into the composite formulation to enhance the reinforcement capability of WF (50 wt%), improving the coilability of filament, and continuous printability of the provided filaments without nozzle clogging issues. Such advancements, especially in WF:PLA composites, are key to expanding the application of 3D printing in high-demand sectors such as construction and automotive, aligning with global sustainability efforts by conserving wood resources and reducing the impact of fossil fuel-based plastics. This research illustrates how custom material solutions could significantly enhance 3D printing capabilities, paving the way for more sustainable, efficient, and versatile manufacturing practices.

Austenitic high Manganese (Mn) steels have many attractive properties, including high toughness, wear resistance, and work hardenability, which make them a material of choice for rock crushing and sizing operations. In this study, the effect of Titanium (Ti) addition and heat treatment on the microstructure, Charpy impact toughness, and dry sliding wear resistance of High Mn Steel (HMS) alloys was investigated. The addition of Ti resulted in the in situ precipitation of TiC particles homogeneously distributed throughout the microstructure. It was observed that the precipitation of TiC particles contributed to grain refinement in the as-cast and heat-treated conditions. The precipitation of the TiC particles was also seen to increase the impact toughness and the dry sliding wear resistance of the alloy as-cast and solution annealed conditions. This improvement in the mechanical response of the Ti-modified HMS alloy was attributed to a combination of grain refinement and dispersion strengthening.

Metso has developed its own advanced modular precursor (pCAM) plant process solution based on Metso’s existing technologies, allowing cost-effective and sustainable pCAM production that meets a continuously increasing need for battery material. Modularity and new all-in-one precipitation reactor solution will add the needed flexibility to increase production capacity step by step and produce different types of co-precipitated precursor chemistries while realizing cost-savings in start-up or expansion phases. The efficiency of the pCAM process will increase through the use of Metso online analyzers. Online analyzers can be used, for example, to control metal concentrations of the feed solution or to measure the particle size of precipitated precursor. When on-line analyzers are connected to the process, the need for laboratory analysis decreases and more real-time data becomes available for process control. Automated process parameter control can be built based on the analysis results because on-line analysis enables fast reactions to changes in the metallurgical behavior of the process, thereby increasing production rate and decreasing downtime and the amount of off-spec material. The benefits of the modular Metso pCAM plant solution include (1) the precipitation process can be operated in several modes (batch, semi-batch, or continuous), (2) on-line particle size and metal solution analyzers control precipitation, and (3) advanced automation (digital solution) can automatically predict and control process parameters.

In recent times, wire-arc additive manufacturing (WAAM) has emerged as a versatile and highly productive method for producing various structural materials. This innovative technique has garnered significant attention across multiple industrial sectors, owing to its adaptability and efficiency. In this study, St-52 alloy steel samples were manufactured by the WAAM method on St-37 alloy steel substrate employing different fabricating angles of 60°, and microstructure was investigated. Observing the melt-pools has yielded valuable insights into the impact of the arc’s heat on the substrate microstructure. This occurs during the entire cycle of wire melting and subsequent solidification in the WAAM process, with consistent process parameters maintained across all samples. Notably, finer microstructures were observed in the top layers across all strategies. However, as the angle of the initial additive layer decreased, there was a significant increase in heat effects on the substrate, leading to a broader area impacted by the arc’s heat input. Moreover, in the recrystallized microstructure, the grain size at the interfaces transformed into the subsequent layer until the layer’s manufacturing concluded.

Architected metamaterials, a subset of hybrid materials, can offer multifunctionality through their tuneable architectures for a wide range of applications. Recently, multiple literature studies have independently shown that the introduction of aperiodicity (i.e. topological defects) in architected metamaterials can enhance damage tolerance, strength, and energy absorption. This behaviour imitates that of grain boundary structures in polycrystalline metals and is particularly attractive in the design and manufacturing of 3D printable orthopaedic implants. Thus far, a systematic mechanical investigation of this new class of metamaterials has not yet been conducted. In this study, we investigate 3D printed polymeric-mesoscopic 2D honeycomb structures and assess the role of a unique kind of topological defect consisting of a pentagon and heptagon pair (referred to as 5–7 defects) arranged to mimic dislocations found in graphene. Similar to a crystal where the accumulation of dislocations forms a grain boundary, here the arrangement of 5–7 defects forms a domain boundary (a “meta-grain boundary”). We designed a range of honeycomb bidomain structures with various arrangements of 5–7 defects creating domain boundaries based on different misorientation angles. These honeycomb structures were fabricated using additive manufacturing (Digital Light Processing DLP 3D printing) and subjected to mechanical testing (quasi-static in-plane compression). Finally, the confluence of experiments and finite element simulation demonstrated that the arrangement of the 5–7 defects has a significant impact on the properties and failure mechanism of the honeycomb bidomain structures.

This study explores the multifaceted challenges in fabricating polar icebreakers, particularly in light of the escalating effects of global warming on the Arctic region. As Arctic ice melts, a shorter trade route between Asia and Europe emerges, highlighting the need for efficient polar-class vessels. However, the harsh conditions posed by extremely cold climates significantly impact the performance of icebreaker hulls, requiring careful selection of steel grades for optimal strength, toughness, weldability, and cost-effectiveness. Given frequent collisions with ice blocks, prioritizing hull steels with high-impact energy in low temperatures is imperative. Therefore, careful selection of marine steel with a minimal ductile–brittle transition temperature (DBTT) emerges as a crucial factor in enhancing the safety of ship hulls in subzero conditions. The DBTT is intricately linked to the chemical composition and microstructural features of the steel, underscoring the significance of these factors in determining the steel’s performance under challenging environmental conditions. Ensuring the precise chemical composition of marine steels and employing suitable heat treatment and thermomechanical processing are vital for enhancing the microstructure and, consequently, the mechanical properties of marine steels in subzero temperatures. Optimizing processing parameters facilitates the development of acicular ferrite, enhancing toughness at low temperatures. In shipbuilding, welding is pivotal and necessitates customized methods for each marine steel grade, considering thickness, chemical composition, and mechanical properties. Careful selection and customization of welding methods, combined with precise adjustment of process parameters, are crucial to ensure the optimal performance and durability of marine steels in polar icebreaker applications.

The Laser Metal Deposition (LMD) technique, a rapidly advancing additive manufacturing (AM) method, is gaining significant attention. This research focuses on the utilization of LMD for fabricating Inconel 718 alloys, vital in aerospace and automotive industries. Examining various process parameters, especially scanning speed variations within LMD, the study investigates their impact on solidified microstructures and their correlation with corrosion resistance in printed components. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) techniques analysed the microstructural and compositional features of as-printed LMD samples. Electrochemical tests in NaNO3 solution further assess corrosion mechanisms. The findings reveal dendritic morphology in LMD Inconel 718, with primary columnar grains. Alterations in scanning speed influence grain size, reducing it by approximately two times at 850 mm/min, potentially affecting corrosion resistance. The study emphasizes the role of micrograin texture and morphology in determining the corrosion behavior of the investigated samples.

For innovation at the industry level, Giffard makes the argument that innovation at the industry level is non-linear because of the varying and iterative capabilities of individual firms (Giffard, Making jet engines in World War II. University of Chicago, 2016). History says that the firms that have had the most success with innovating with the new technology are those that have been able to leverage their preexisting capability to accelerate innovation with the new technology.

In this study, the impact of post-printing heat treatment on an arc-directed energy deposition (arc-DED) fabricated nickel-aluminum bronze (NAB) alloy was thoroughly evaluated, aiming to tailor its microstructure for enhanced mechanical properties compared to the as-printed state. Microstructural analysis, conducted using scanning electron microscopy with energy dispersive spectroscopy (EDS) and X-ray diffraction, identified the presence of lamellar κIII (NiAl) and globular κII (Fe3Al) phases as intermetallics embedded within the α-phase matrix (Cu-matrix) in the as-printed arc-DED-NAB. The as-printed alloy demonstrated a yield strength (YS) of 314 MPa, ultimate tensile strength (UTS) of 643 MPa, and 31% elongation along the building direction. Subsequent to the printing process, two different heat treatment cycles were performed on the as-printed alloy, that is, solutionizing followed by aging, and direct aging. Solutionizing at 950 °C for 2 h, followed by quenching and aging at 675 °C for 6 h, yielded UTS and YS of 691 and 335 MPa, respectively, with 25% elongation. Differently, direct aging of the as-printed alloy at 675 °C for 6 h resulted in a higher UTS and YS, recorded at 716 and 354 MPa, respectively, while elongation reduced to 23%. This study concludes that direct aging alone provides the most favorable combination of strength and ductility, resulting in the formation of globular κII and the coarsening of needle-like κV, and the complete spheroidization of lamellar κIII, compared to the solutionizing, quenching, and aging heat treatment process.

In recent years, sustainable design research has increasingly focused on the circular economy, aiming to extend material life and recover materials completely, thereby enhancing material stability. This approach seeks to maintain product value while minimizing waste. Additive manufacturing (AM), also called 3D printing, is recognized for its potential contribution to this paradigm by enabling sustainable materials development. AM facilitates improved manufacturing solutions that align with the circular economy, particularly by encouraging polymer recycling and reuse. However, there is a gap in research exploring this relationship. Addressing this gap, this study introduces a novel biocomposite formulation tailored for extrusion-based 3D printing. The composite utilizes recycled PET from water bottles and biomass waste fillers. Various formulations incorporating biomass and additives were tested for optimal rheological properties and printability. The research demonstrates the potential of the 3D printed recycled composite for applications in automotive, construction, and aerospace industries, aligning with circular economy principles and sustainable manufacturing by utilizing recycled materials in sustainable manufacturing processes.

Microstructure control in additive manufacturing is challenging. Therefore, understanding the thermal aspects is necessary for an efficient application of technology. Nickel-aluminum bronze is a high-value alloy for seawater service. Traditionally used by casting, its properties are significantly improved by additive manufacturing. This is partly due to the complex sequence of phase transformations that may occur. In this work, the effect of processing parameters such as wire feed speed and travel speed, on microstructure, is explored. These processing parameters have a profound effect on the material phase transformations. Hence, predicting the reheating, let alone understanding its resulting microstructure, constitutes a major challenge. Thus, the value of the present work lies in exposing the effect of a single reheating, and how this may change with processing parameters. This work serves as a base for future, more detailed observations on microstructural transformations.

Advanced manufacturing, and in particular additive manufacturing or “3D printing,” involves creating products through layer-by-layer addition and subtraction of materials using 3D printer in accordance with a CAD file containing a design. However, the ubiquity of 3D printing equipment, and differences in manufacturing approaches using 3D printing as compared to traditional manufacturing approaches, creates several intellectual property challenges, such as (a) products created by AM may not be protected by patents drafted with conventional manufacturing techniques in mind, (b) the ability to create AM products using only a 3D printer creates potential for a large number of infringing parties, and (c) 3D printers can be geographically located close to points of sale of products, rendering conventional border detection methods ineffective. These challenges are expected to have a direct impact on automotive companies based in developed economies, which typically focus their business model on only developing and manufacturing products that can be protected through some form of intellectual property protection, such as by patent or design.Recommendations to address these challenges in the automotive sector are provided.

The impurity management in flash smelters has become more and more challenging and important in recent years. HSC Sim modelling tool was used to quantify arsenic flows in various processing steps under different scenarios in the flash smelting process. The model covered the processing chain from copper concentrates to copper anodes, and the gas line part included the waste heat boiler and the electrostatic precipitator. The effects of arsenic concentration in the feed, matte grade, and dust circulation are discussed based on the modelling results. Temperature has a significant influence on impurity behaviour as the impurities evaporate and condense in different parts of the process depending on the temperature. To better understand the behaviour of volatile impurities, such as arsenic, lead and antimony, laboratory-scale experiments were conducted under controlled conditions with a newly developed experimental equipment setup using arsenic as a model impurity. The intention is to expand the methodology to other impurities after the link between laboratory experiments and industrial behaviour is established.

Mitsubishi Materials Group (MMCG) promotes the processing of E-Scrap at Naoshima Smelter & Refinery (Naoshima) and Onahama Smelting & Refining Co., LTD in Japan. The increase in E-Scrap treatment amount makes the kinds and amounts of metals enter the process of copper and precious metals smelting increase. Lead, bismuth, antimony, and tin are impurity metals for copper smelting and refining and precious metals smelting. Therefore, it is important to extract impurity metals and recover them as valuable metals for expanding the E-Scrap business. Hosokura Metal Mining Co., LTD (Hosokura) is the only lead smelter & refinery of MMCG. Hosokura has received lead residues from copper smelting and precious metal smelting at Naoshima, and Hosokura has recovered lead, bismuth, antimony as products, and gold, silver as crude silver. However, Hosokura was not able to recover tin from lead refinery process, and part of tin contained in copper matte was returned to Naoshima. In 2018, the tin recovery process was developed by Mitsubishi Materials Co., LTD (MMC). In the process, tin is recovered as burtite (CaSn(OH)6) from Harris dross. The recovered burtite is sent to MMC’s Ikuno Plant (Ikuno) that produces electrolytic tin. In July 2020, Hosokura started operation of the plant to recover burtite from Harris dross, and in August began sending the burtite to Ikuno. This report introduces the newly started tin recovery business of MMCG.

As time progresses, more copper deposits with higher arsenic are exploited leading to higher arsenic in concentrates delivered to copper smelters. Arsenic is often associated with antimony; hence, it is judicious to develop refining processes that consider both. Copper electro-refineries can process copper anodes containing up to 2000 ppm of arsenic, higher levels potentially impacting the process. This paper discusses the use of conventional fluxes (Na2CO3 and CaO) for the control of As and Sb in anode copper. The behavior of other minor elements is also discussed (Ni, Bi, Pb, Se, and Te). Major factors affecting As and Sb elimination efficiencies are reviewed (flux addition, %CaO/%Na2CO3 ratio, and oxygen content in blister copper). Mechanisms for refractory corrosion are also reviewed as well as slag recycling practices. Using the Factsage software and available thermodynamic databases, process maps were prepared portraying operating windows, arsenic and antimony in anode copper and saturation lines.

There is a need to identify alternative compounds for arsenic remediation that exhibit higher phase stability than those generated using conventional methods. The first step in assessing the possibilities is through chemical-thermodynamic simulations. It is known that some rare earth arsenates are highly stable, however, rare earth element (REE) arsenate thermodynamic data are limited. Hence, an overview of lanthanum (La), neodymium (Nd), and cerium (Ce) chemical stability was performed under different systems scenarios (i.e., aqueous only, arsenate, sulfate, or chloride). It is found that the REE arsenate is stable over a broad pH range, and incongruent dissolution or phase transformation (e.g., hydroxide) is expected at highly alkaline conditions. Chloride did not influence the solubility of the arsenates, whereas sulfate increased solubility in the region where LaSO4+ and NdSO4+ species are predominant (pH < 10). Metastability simulations were not considered, and the phases were compared regarding their equilibrium thermodynamic stability alone. Iron (Fe) is commonly used as a source for arsenic removal and has been widely studied. It was used here as a baseline for comparison with La and Nd arsenate stability. An experimental investigation into REE arsenate stability is currently underway, and a more detailed discussion and evaluation will be published in the near future.

Arsenic contamination is a global environmental problem. Trivalent arsenic As(III) can be commonly found in nonferrous metal smelting wastewater, which is more toxic and challenging to remove compared to pentavalent arsenic As(V). Therefore, the key step in arsenic pollution control is to oxidize As(III) to As(V). Tooeleite (Fe6(AsO3)4(SO4)(OH)4·4H2O), the only known ferric arsenite sulfate-bearing mineral, exhibits the potential to directly remove and stabilize As(III) in wastewater. A novel chemical mineralization method was developed for the direct removal of As(III) based on the control of the precursor mineral phases. The mineral transformation processes involved the adsorption of arsenic onto ferrihydrite, then the amorphous tooeleite formation, and the rapid mineralization of amorphous precursors. Novel methods for enhancing tooeleite mineralization with carboxylic acid organics and seed crystal induction were proposed, and this breakthrough achieved the leaching content of arsenic in synthetic tooeleite below the standard limit of 5 mg/L for the first time. In addition, our research group has carried out studies on biomineralization. The effect of Acidithiobacillus ferrooxidans on the morphology evolution of mineral formation was elucidated, the arsenic-containing ferric sulfate was formed as a precursor and then the precursor was dissolved and recrystallized to tooeleite. Furthermore, a cocultivation system of Acidithiobacillus ferrooxidans and Acidiphilium acidophilum was established for biomineralization research. This cocultivation system has achieved a 45% improvement in the arsenic stabilization efficiency, with a minimum arsenic concentration required for mineralization as low as 200 mg/L. Biomineralization technique holds great promise as a green and ecological approach for arsenic stabilization.

Kosaka Smelting and Refining Co., Ltd. is a copper and lead smelter in Japan. In 2008, the flash smelting furnace was replaced by the TSL furnace, and raw materials changed from ores to E-scraps. This change increased the amount of antimony sent to lead smelting division. Thus, it was necessary to improve lead smelting process and start up a new antimony recovery process to treat higher quantity of this element. The lead refining process was improved to solve anode hardening and increase caused by antimony. As a result, the limit of antimony concentration in anodes was raised from 2.0% to 4.2%. In the antimony recovery process, this element is leached by fluorine. Some fluorine is lost as wastewater and supplied by hydrofluoric acid. To improve the cost of hydrofluoric acid, we installed fluorine recovery process utilizing diatom earth. In this report, we introduce the antimony recovery process at the Kosaka smelting.

Kosaka Smelting and Refining Co., Ltd. installed tin recovery process in 2012 and produces around 550 tons of tin annually. Tin is contained in E-scraps. E-scraps are processed in a TSL furnace, and tin is recovered as dust with lead. The dust is processed in a lead electric furnace and tin is distributed to crude lead. Agitating the molten crude lead, tin is oxidized into the form of dross and separated from lead. Tin metal is produced from dross through both pyrometallurgical and hydrometallurgical sections. In the future, Kosaka plans to expand E-scraps processing capacity and increase tin production. To achieve this plan, it is necessary to improve the productivity of tin recovery process. Since conventional air oxidation process for tin took a long time, this oxidation process was a rate-determining step in the lead refining process. When tin input increased temporarily, it was necessary to reduce the amount of charge to the lead electric furnace. To solve this problem, oxidation process was reviewed. This improvement increased the separation speed and made it possible to maintain a high charge amount to the lead electric furnace. In the electrolysis process, dendrites and spongy electrodeposition caused short circuit and increased dross generated during dissolution. By changing the management of the electrolyte, the electrodeposition state became smooth, and dross generated decreased. In addition, we will report the high-purity tin in the electrolysis process.

The acidic wastewater discharged from the nonferrous industry contains multiple metals with extremely complex components. Due to the low solubility product of metal sulfides, traditional sulfidation methods are prone to supersaturation, leading to coprecipitation. The efficient separation and resource utilization of multiple metals have always been an internationally recognized challenge. In response to these challenges, the research team has pioneered a novel idea for the cascaded separation and recovery of multiple metals through gas-liquid sulfidation. Studies focused on sulfide separation, particularly copper-zinc and copper-arsenic, were conducted. Our team established the relationship between hydrogen sulfide-enhanced mass transfer and sulfur concentration control, elucidated the characteristics of the gas-liquid-solid three-phase interface, revealed the sulfurization reaction mechanism,achieving efficient separation and recovery of metal sulfides. Compared to the current sodium sulfide method, the developed jet gas-liquid mixer and cascaded sulfidation reactor exhibited a tenfold increase in reaction rate. Direct separation of multiple components in acidic waste solutions has been realized, achieving a separation rate of 99% for challenging elements such as copper-arsenic and copper-zinc. The new technology and equipment have been implemented in over 20 national industrial applications. Internationally, this approach stands as a pioneer in achieving clean recovery of smelting acid and substantial reduction of hazardous waste.

Liberator cells are a common method of removing arsenic, antimony, and bismuth from copper electrorefining circuits. Reduction of arsenic involves a risk of toxic arsine gas formation, which must be mitigated by having appropriate conditions in the electrowinning cell. Laboratory-scale experiments are required to find these conditions and improve liberator cell function. The formation of arsine gas must be reliably detected. In this study, the suitability of the silver diethyldithiocarbamate (AgDDC) spectrophotometric method for arsine gas detection and quantification was studied. This study aimed to assess the suitability of the analysis method with the context and demands set by real hydrometallurgical experiments in mind.

Glencore’s Horne Smelter is a custom copper smelter located in Rouyn-Noranda, Canada. Over the past decade, substantial development work has been made to modernize its process. In line with the internal development of the Noranda Reactor (1970s) and Noranda Converter (1990s), a new approach using ladle metallurgy has been developed for converting and refining of semi-blister copper in a single step into anode copper, thus replacing the pyro refining vessels (Peirce-Smith converters) and anode furnaces. Extensive development work and piloting steps were conducted over the last decade to conclusively demonstrate the performance of this technology, allowing for its full-scale implementation. Under the name of Aeris, the project is focused at increasing efficiency and improving the smelter’s environmental performance. The new process is planned to be commissioned in 2027. This paper presents the rationale behind the technology selection, the development of the application of ladle metallurgy in copper converting and refining, and the overall smelter modernization plan.

The issue of arsenic stabilization at base metal smelters is pressing and challenging. As the demand for copper increases and “clean copper” deposits become both depleted and scarcer, base metal concentrates are expected to contain higher grades of arsenic. At the same time, arsenic waste management regulations continue to tighten globally. The vast majority of arsenic that is imported from mines into smelting operations ends up reporting to weak acid solution blowdown from gas scrubbers which contains high sulphate levels and a host of metals and metalloids. The status quo method of blowdown treatment is addition of lime and/or ferric salts to precipitate arsenic along with most other metals, metalloids, and gypsum into a waste sludge. The two main issues with this arsenic management method are that the tonnage and volume of the waste sludge are high, and the stability of arsenic and other metals in the sludge is low. Recently, the Glasslock process that involves vitrification of arsenic-rich solids has been commercialized. However, Glasslock is not suitable for vitrification of solids produced by the status quo treatment of weak acid blowdown. Arsenic “deficient” smelters have practiced arsenic trisulphide precipitation for decades. Although the production of As2S3 offers many advantages, the often-quoted disadvantage of using A2S3 is the lack of As stability in the solids which the smelters avoided by recycling As2S3 solids back to the furnace. This paper examines several options for enhanced arsenic stabilization using As2S3 production including encapsulation of As2S3 in a gel matrix and a combination of As2S3 production with Glasslock.

Wastewater containing arsenic (As) from industrial processes such as non-ferrous smelting has a significant environmental impact due to its high toxicity. There is a need for a method to immobilize arsenic in a stable form suitable for final disposal or long-term storage. Immobilization of arsenic in the form of scorodite (FeAsO4·2H2O), which has excellent chemical stability, is attracting attention as a method for treating wastewater containing high concentrations of arsenic. Scorodite, with its low solubility and high arsenic content per volume, is expected to be an environmentally friendly arsenic fixation method. Among various types of methods, scorodite synthesis using solid iron oxides such as Fe2O3, Fe3O4, and FeOOH as Fe sources has been investigated in recent years with great enthusiasm as a low-temperature scorodite synthesis method under atmospheric pressure. For the synthesis of crystalline scorodite at atmospheric pressure, the in situ oxidation of Fe(II) to Fe(III) in As(V)-containing solution is known to be important. However, the study of the redox reaction of Fe(II) in arsenic-containing solution is very limited. In this presentation, we will report the result of the analysis of the electrochemical behavior in the As(V)-Fe(II)-H2O system using electrochemical methods. In addition, the electrochemical involvement of Fe(II) in the scorodite synthesis by the iron oxide addition method, which significantly accelerates the reaction, will also be presented. The mechanism of the spontaneous redox reaction of the oxidation of Fe(II) to scorodite and the reduction of solid iron oxide containing Fe(III) was elucidated by the electrochemical analysis using solid iron oxide electrodes.

In this paper, recent advances made in the atmospheric scorodite process originally developed at McGill and later commercialized by Ecometales in Chile are presented. The original process allowed for crystallization of well-grown scorodite solids via supersaturation control and seeding regulated by stepwise adjustment of pH with lime. As a result, the produced scorodite was obtained mixed with gypsum reducing the %As content in the disposed solids from 30% down to ~10%. Motivated to make clean scorodite (free of gypsum) for compact disposal (near 30% As content), a new generation of atmospheric scorodite process has been developed in which supersaturation is controlled by iron dissolution/leaching. In other words, the process is controlled by the rate of iron dissolution. This has been demonstrated with goethite, magnetite, and iron(III) oxyhydroxide but other iron sources like hematite or metallic iron may be used too. The process involves the addition of the iron (hydro)oxide solids to acidic solution of As(V) in the absence of lime. Essentially, the iron solids act both as a source of iron but also as a neutralizer. In this chapter, laboratory batch test results are reported along a conceptual flowsheet that integrates oxidation of As(III) with SO2/O2 and scorodite production by iron dissolution.

The late John Higginson referred to arsenic, cadmium, mercury, and thallium as the big bad four when it comes to closing the loop on processing nonferrous concentrates and secondary materials from urban mining. As nonferrous smelting companies move to become more sustainable by closing their flowsheets so that they do not generate “residues” for “landfilling” and societal demand is declining, or has declined, these elements need to be managed for “permanent” storage. Understanding the proposed chemical and physical forms and storage conditions, with their associated failure mechanisms that could lead to the release of the elements to the environment, is required to determine appropriate tests to assess and compare the long-term performance and sustainability of proposed “permanent” homes for these elements.

Calcium arsenic (As) residues (CARs) have high arsenic solubility in the environment and hence need stabilization treatment. In this work, a novel method was proposed to leach the As and valuable metals from CARs with As-containing waste sulfuric acid (WSA) followed by immobilization of arsenic as scorodite. The results showed that 93.5% of As and almost all the valuable metals in the CARs were leached out in 10 h. After precipitation of scorodite, most of the valuable metals in the residual solution were recovered by precipitation as metal (hydr)oxides. This work provides a novel method for simultaneous treatment of CARs and WSA.

Incorporation of arsenate (As(V)) and sulfate species into the ettringite (Ca6Al2(SO4)3(OH)12·26H2O) structure has been considered as a process for arsenic and sulfate fixation in the treatment of an industrial effluent treatment containing 2044 mg/L of sulfate and 24 mg/L of arsenic. Precipitation was carried out with distinct molar ratio of Ca:Al:SO4, lime as a calcium source, and a combination of aluminum polychloride and Al(OH)3 as aluminum supply. Experiments were guided by thermodynamic modeling on PHREEQC which indicated pH 11.5 as the best value to remove sulfate and arsenic simultaneously from this wastewater. This was essential to avoid subsequent sulfate release from ettringite at higher pH due to the formation of Ca4Al2O7:19H2O. Both ettringite and ettringite-As precipitation, at pH 11.5, dropped down the sulfate and arsenic residual concentration to 4 mg/L and < 0.05 mg/L, respectively. The final effluent presented parameters within the acceptable limits of 0.2 mg/L of As and 250 mg/L for sulfate in Minas Gerais State-Brazil.

Environmental regulations are very strict for selenium requiring its removal from various streams down to <5 ppb. In this context, selenate, Se(VI), that is often encountered in waste waters originating from mining, metallurgical, chemical, and semiconductor industries, imposes particular challenges to its effective elimination due to poor adsorption and reduction. In this work, the effective removal of Se(VI) down to 5 ppb level is described via the use of nano zero-valent iron, nZVI, that acts as a strong reducing agent. Emphasis is given on elucidating the galvanic mechanism of selenate reduction and immobilization on nZVI surface with the view of achieving increased electron efficiency that translates to selectivity against the undesirable excess consumption of nZVI by parasitic hydrogen evolution without sacrificing environmental effectiveness. Through extensive nanoscale surface characterization, the Se uptake mechanism was determined to involve (1) selenate reduction to selenite via reductive adsorption on the hydrous Fe(II)-oxide surface of nZVI and (2) sequential galvanic reduction to elemental selenium through the Se-enriched Fe(0/II/III) oxide layer. It was found the formation of Se0 nanoclusters on nZVI to play a significant role in enhancing the selective reduction of selenium while simultaneously suppressing the parasitic evolution of hydrogen. These findings may lead to further testwork on the design and application of stable nZVI systems yet with high efficiency and effectiveness for reductive elimination of hazardous species of environmental concern.

Zijin Mining Group initiated a R&D program in 2017 to address arsenic control challenge encountered in smelting of copper concentrate containing high arsenic. Following successful development of a new process for immobilizing arsenic in acidic effluent as an environmentally stable material, a commercial plant with design capacity of treating 600 m3/d waste acid containing 15 g/L As and 150 g/L H2SO4 was built in 2019 in Zijin Copper Smelter. It involves limestone neutralization of waste acid effluent to produce a clean gypsum by-product, arsenic oxidation, precipitation of scorodite under atmospheric condition, and a polish step to generate arsenic-free water for reuse or discharge. The plant was commissioned in December 2019 and full performance was achieved in 2 months. The up-to-date plant operation results show that the developed arsenic control process is technically and economically viable. The scorodite-based material produced in the process contains arsenic up to 25 wt.% and can meet both the US EPA TCLP (As<5 mg/L) and Chinese TCLP (As<1.2 mg/L) standards for disposal. The overall cost for arsenic stabilization including arsenic material disposal was in the range of US $2000–3000 per ton of arsenic stabilized.

During the last decades, waste generation has increased enormously as a result of the activities of the exploitation of resources, raising environmental concerns in communities around the world. To tackle this issue, the industry must find new ways to recycle and reduce the generation of waste in the so-called circular economy. Since 2007 EcoMetales, a Chilean company subsidiary of Codelco, has been contributing to the field of value recovery and stabilization of deleterious elements from mining waste. The EcoMetales industrial site is located in Calama, close to the Chuquicamata copper smelter and the Ministro Hales Roaster Plant, both Codelco operations. Additionally, a fully equipped metallurgical laboratory and pilot plant for assessing new technologies is located on the industrial site. An overview of the company in the processing of metallurgical residues, as well as a review of the different technologies developed for the mining sector, is presented in this keynote conference.

Copper is of importance for the development of upcoming technologies. The majority of copper is extracted by smelting of copper concentrate obtained from copper ores after flotation. However, these concentrates may possess a mineralogical bonded content of As and other impurities, for example, Sb and Bi, which constitute penalty elements. The removal of these elements is necessary due to their negative influence on the copper refinery process. In addition, the cost-effective production of arsenic-poor copper concentrates for smelting is important. The purpose of this study was to develop a low-cost, tailor-made approach for alkaline sulfide leaching to produce an arsenic-poor copper concentrate. Whereby, kinetics of arsenic dissolution were studied to develop and establish the reaction mechanism and control mode. Leaching kinetic models for arsenic reduction from two different Chilean copper concentrates, which contain both Enargite-Tennantite (as main As-containing minerals), are presented in this study. At first, the key leaching parameters for arsenic removal by alkaline sulfide leaching, such as temperature, sodium sulfide and hydroxide concentrations, and solid-to-liquid ratio were optimized. Under the studied conditions, arsenic removal achieved at T = 80 °C, [NaOH] = 2.5 M, [Na2S*3H2O] = 2 M, and solid-to-liquid ratio = 1/10 g/mL was similar to that obtained during partial roasting. Then, kinetic models for arsenic removal were developed. It was discovered that during the early phases of leaching, the dissolution kinetics of As are controlled by both chemical reaction and diffusion at the product layer generated on the outer surface of Enargite or Tennantite. Later, As dissolution is completely controlled by diffusion at the product layer.

Due to the aging of ore deposits, there has been an increase in the content of impurities resulted in a higher content in copper concentrates, where Chile and Peru are both the largest producers worldwide, accounting together around 7.8 Mt/y. Among the different deleterious elements of copper concentrates, arsenic is among the most challenging for smelting and refining operations. Roasting is a key technology for handling high Arsenic (As), where this element is contained in flue dust or weak acid effluents requiring further treatments for its stabilization. Around 95 kt of arsenic is generated each year by the mining industry worldwide, overpassing the market demand. The industry in facing a big challenge in finding new ways to environmentally dispose of arsenic both in a stable form but also minimizing waste generation. Up to date, scorodite is one of the most stable forms for arsenical disposal; however, the technology for processing weak acid effluent requires the neutralization of residual sulfuric acid ending up with a residue with a mixture of scorodite and gypsum if calcium is the neutralizer of choice resulting in a relatively low arsenic content residue. Recently, EcoMetales has developed a process where in a certain range of sulfuric acid concentration a substantially free gypsum scorodite can be produced. The effect of different parameters was evaluated at a laboratory scale and proved the concept in the pilot plant with industrial effluents. Further, industrial tests are planned for the first semester of 2024 to validate the technology. In this work, the key aspects of this process, covering from lab-scale tests to industrial trials, are presented.

Copper sulfide concentrates (CSC), processed by smelting to produce copper anodes, may contain precious metals as well as metalloids (e.g., As, Te, and Sb) that partially volatilize during pyrometallurgical processes, presenting operational and environmental challenges. Their selective separation from CSC prior to smelting could improve critical elements supply and bring numerous benefits, which would be reflected in lower penalties imposed by the smelter. Alkaline sulfide leaching (ASL) can selectively extract some of these deleterious elements from CSC. In this paper, ASL was studied as a CSC cleaning method, with the global objective of documenting the leaching behavior of several deleterious and critical element-bearing minerals. Two CSC samples were characterized for chemical and mineralogical composition, as well as particle size distribution. A series of lab-scale ASL tests were performed to evaluate the effect of leaching time, oxygen ingress, number of leaching steps, and regrinding on targeted elements removals. Extractions up to 16%, 74%, and 51% were obtained for As, Te, and Sb, respectively, after 6 h using 75 g/L NaOH, 60 g/L Na2S at 80 °C. Tests showed that oxygen ingress in ASL of the CSC did not improve extraction, while regrinding prior to ASL had a positive effect on the extraction of Sb. Finally, mineralogical analysis shows that both leachable and non-leachable species are present and suggest that the rate of leaching of some species may be limiting the final extraction. This study demonstrates the potential of selective leaching as a means of recovering metals and separating value-added elements, while simultaneously lowering the content of deleterious elements burden in CSC.

Vale Base Metals has operated the Long Harbour Processing Plant (LHPP) since 2014. The hydrometallurgical process facility includes a concentrate re-grind circuit, pressure oxidation autoclaves, neutralization and impurity removal circuits, and electrowinning to recover nickel, cobalt, and copper metals. Waste streams from the various processing stages are neutralized with residues deposited into a subaqueous storage area near the plant site. The plant was designed to process low-arsenic content Voisey’s Bay sourced nickel concentrate (<0.001% As). In 2016, nickel concentrate from Vale’s Manitoba Division containing up to 0.1% arsenic was investigated as a possible candidate for recovery via the Long Harbour flowsheet. Test work was conducted at Vale’s Technology Center in Mississauga, Ontario, on the unit processes of autoclave leaching, arsenic fixation, final neutralization of both leach solutions and residues, and examination of residue stability over an 18-month period. With positive results, a plant trial was initiated in late 2021/early 2022 validating arsenic could be stabilized on the commercial scale and adhere to environmental regulations related to its deposition in the residue storage area. This paper discusses the challenges and opportunities associated with processing Manitoba nickel concentrate at the Long Harbour Processing Plant.

At Saganoseki Smelter and Refinery of JX Metals Smelting Co., Ltd., work is underway to increase the ratio of secondary raw materials and to reduce the use of fossil fuels by utilizing the oxidation heat generated during the processing of copper ore. We consider that the copper produced through this unique and environment-friendly “Green Hybrid Smelting” process will meet our dual mission of building stable supply structure to meet the increasing demand while establishing production and supply chain focusing on decarbonization and enabling circular economy. As part of our efforts to increase the recycling ratio, the amount of impurity elements in the secondary raw materials such as nickel, antimony, bismuth, and lead, which can have undesirable effects on copper electrorefining process, is increasing as well. In this paper, the improvements in the capacity of impurity removal in the copper electrorefining process and the precious metal treatment process are described.

This study traces the partitioning of arsenic and other minor elements in two primary copper production flowsheets. The first flowsheet employs calcium ferrite slag during the converting stage, while the second utilizes a fayalite-based type of slag. The calculations are conducted using the self-consistent thermodynamic database within the Pb-Cu-Fe-O-S-Si-Al-Ca-Mg-Zn-Ni-Sn-As-Sb-Bi-Ag-Au-C-N-H chemical system and FactSage software operated by the Macro code. The model incorporates recycled streams and considers nonthermodynamic factors identified through literature analysis, with a focus on mechanical dust carryover and nonequilibrium arsenic evaporation. Furthermore, this study establishes a connection between the fundamentals of slag chemistry, slag/matte distribution coefficients, and the fate of arsenic, as well as other minor elements in the process.

Partial roasting is an efficient technology for de-arsenifying As-containing Cu-concentrates, where As is contained typically in enargite (Cu3AsS4) and tennantite (Cu12As4S12). The operation of the Codelco DMH roaster train (roaster, gas cleaning, acid plant, and effluent treatment plant), supplied by Metso, at >100% load is discussed. Chemical transformations lead to a de-arsenified chalcopyrite (CuFeS2)/bornite (Cu5FeS4) roaster calcine to be fed to a Cu-smelter upon blending with high S-grade feed. The typical calcine As-content is <0.3 wt% and the S-grade is approx. 20 wt% for a concentrate S-feed grade of 35 wt%. The fluid-dynamics of the roaster rely on entraining the bulk of the calcine and maintaining a SiO2 rich bed. Thereby, calcine residence time is limited, hence pointing to rapid arsenic removal rates. Calcium arsenite (practiced at Codelco DMH) or calcium arsenate stabilization is questionable. Scorodite (FeAsO4*2H2O) is accepted as one of the most stable As-compounds. The weak acid stream (15 g/L As, as HAsO2) produced within the wet gas cleaning section of the roaster train can be used to produce scorodite. Opportunity lies in clean scorodite processes exhibiting an As content of 25–30 wt% in the residue to be disposed. In addition, added stability can be achieved through scorodite encapsulation with use of aluminum gel.

The prevention of anode passivation is one of the major technical hurdles to stabilize high current density operation in copper electrorefining. Its mechanism is considered that the dissolution rate of Cu2+ from the anode increases under high current density and the Cu2+ concentration near the anode reaches its saturated concentration, causing slime deposits on the anode surface. Impurities in the anode are considered for their contribution to the anode passivation phenomenon. Arsenic has a strong influence on passivation. A low arsenic content leads to an increase of the passivation risk. Dissolved arsenic as As3+ in the electrolyte is oxidized to As5+ by dissolved oxygen under the electrolyte temperature, which is considered to contribute to the decrease of the slime.

Rio Tinto is turning waste or by-products into valuable national resources through innovation across the copper value chain. Collaborating with government, universities, and industry partners, Rio Tinto is creating an ecosystem to mitigate production risk and create socially responsible and economically viable pathways to get new critical mineral resources into the supply chain. Many critical metals are only produced as secondary products. Once primary metals, such as copper, lead, and zinc, are concentrated and smelted, it becomes feasible to separate and extract trace co-product metals such as antimony, arsenic, bismuth, cadmium, selenium, tellurium, and others. Understanding the occurrence and deportment of these metals is crucial for their recovery. However, their low concentration and complex spatial distribution within the ore bodies present a challenge for analysis, mapping, and recovery. Efforts across the copper value stream are revealing new opportunities for developing co-production processes for numerous critical metals including platinum group metals (PGMs), bismuth, indium, germanium, gallium, nickel, cobalt, arsenic, and rare earth elements. For instance, the USA heavily depends on imports of bismuth, primarily obtained as a by-product of primary lead or tungsten mining, and similarly, platinum group metals can be co-products of copper production. Rio Tinto is actively pursuing new process routes for bismuth, palladium, platinum, and other critical mineral co-products from copper processing. Herein, we provide an overview of the efforts undertaken in developing these value streams, from innovation to implementation.

Cooling staves, copper blocks, and cooling plates play a crucial role in metallurgical vessels by efficiently dissipating excess heat from various furnace components to maintain the structural integrity of the vessels. Regulating the optimal thermal conditions within the furnace extends the refractory lining campaign life and contributes to enhancing operational efficiency. However, these cooling components are susceptible to corrosion and degradation in the hostile environment and subsequently exacerbate the risk of water leaks, which then extend beyond immediate risks to include chilling of the furnace hearth, explosions related to refractory cracking and spalling, and damage of surrounding equipment. Assessing the extent and severity of the refractory damage caused by explosions poses a considerable challenge to traditional refractory monitoring techniques such as thermal monitoring. The accurate evaluation of the damage is hindered by the complex interplay of factors, making targeted maintenance efforts elusive. This chapter explores the application of Acousto Ultrasonic-Echo (AU-E) as a non-destructive testing method to assess refractory conditions. Case studies will be presented to illustrate the effectiveness of AU-E in assessing refractory degradation caused by thermal shocks and erosion during normal operational processes, as well as damages caused by explosions, offering valuable insights for optimal plans for maintenance, repair and reline.

The factors promoting hydrogen-related intergranular (IG) fracture in the elastic and plastic regions of tempered martensitic steel were investigated. These trials performed tensile tests after freezing the hydrogen distributions through immersion in liquid nitrogen at −196 °C and thermal desorption analysis (TDA). Specimens precharged with hydrogen to concentrations of 7.4 and 5.7 ppm exhibited embrittlement based on IG fracture in the elastic and plastic regions, respectively, at room temperature (R.T.). Specimens precharged to a level of 7.4 ppm hydrogen did not exhibit embrittlement upon tensile testing in liquid nitrogen at −196 °C. However, the frozen-in hydrogen distribution generated by precharging to 7.4 ppm hydrogen followed by preloading at 1300 MPa in the elastic region at R.T. resulted in embrittlement by IG fracture even at −196 °C. In contrast, precharging to 5.7 ppm hydrogen and preloading at 1400 MPa in the plastic region produced a slight ductility loss at −196 °C but no IG fracture. The results of tensile tests after hydrogen diffusion with unloading at R.T. (at which temperature the hydrogen was able to diffuse) and TDA of the frozen-in hydrogen distributions indicated that reversible and irreversible hydrogen distribution changes occurred in the elastic and plastic regions, respectively. These data suggest that the hydrogen-related IG fracture occurs via different mechanisms in each region.

One of the major sources of catastrophic failures and deterioration of the mechanical properties of materials, such as ductility, toughness, and strength, of various engineering components during application is hydrogen embrittlement (HE). It occurs through adsorption, diffusion, and the interaction of hydrogen with various metal defects like dislocations, voids, grain boundaries, and oxide/matrix interfaces due to its small atomic size. This research was aimed at assessing the tensile properties; toughness, ductility, ultimate tensile strength, and yield strength of cold-finished mild steel samples owing to the diffusion of hydrogen. Samples were subjected to electrochemical hydrogen charging in a carefully chosen alkaline solution over a particular period. Tensile properties tests were conducted immediately post the charging process, and the results were compared with those of uncharged samples. This evaluation has enabled the prediction of the level of embrittlement to expect given a specific hydrogen concentration.

Canada is actively pursuing carbon emission reduction strategies, with a particular focus on hydrogen–natural gas blending as a promising avenue. This approach, while environmentally friendly, might face a critical challenge in the form of Hydrogen Embrittlement (HE), where hydrogen atoms infiltrate pipe steel, leading to mechanical property degradation and potential failures. This study employed rigorous methodologies, including hydrogen permeation and charging tests, and mechanical testing on samples of two distinct pipe steels relevant to natural gas distribution. The electrochemical charging process induced hydrogen absorption, and subsequent tensile and fatigue testing revealed a discernible decline in properties, indicating embrittlement and reduced ductility caused by hydrogen infiltration. These findings highlight the importance of addressing HE for the successful implementation of hydrogen–natural gas blending in emissions reduction strategies.

Arsenic may cause high-temperature corrosion in the gas line or aqueous corrosion in the acid plant of a smelter. High-temperature corrosion was studied by exposing carbon steel, 3R12, and Sanicro 28 stainless steels to an SO2-containing atmosphere at 275 °C for 142 h with and without an As2O3 deposit. The As2O3 deposit did not have any effect on stainless steels but for carbon steel, it enhanced grain boundary oxidation which is in line with the failure analysis observations that As promotes localized corrosion in carbon steel. The influence of As on aqueous corrosion was investigated with immersion tests of 316 L and LDX 2101 lean duplex for four weeks at 95 °C sulfuric acid and chloride-containing solution with and without dissolved As2O3. It was confirmed that As3+ acts as an oxidizer in the same way as metal cations that have several valence states available.

In this work, the effect of hydrogen charging on the hydrogen embrittlement of Grades 359 and 448 pipeline steels is investigated by proof ring test. Hydrogen charging is carried out using a cathodic charging cell. The specimens are inserted into proof rings for constant-load testing under in situ and ex situ hydrogen charging conditions. Furthermore, basic mechanical properties were determined under different charging conditions. It was found that the hydrogen-charged specimens exhibited loss of ductility.

Using a small-cell active learning approach, we generate a moment tensor potential (MTP) trained on only 609 configurations, jointly describing solid/liquid Na, gaseous Cl, and crystalline/molten NaCl. This MTP implicitly captures the effect of atomic charge variations on energies and forces based on local atomic configurations. Extensive testing of this potential points to a high-fidelity description of the structural and transport properties of Na and NaCl. Furthermore, this potential was used to calculate the standard reduction potential and solubility limit of Na in molten NaCl. These computed properties are in good agreement with available experimental data and ab initio calculations. Our proposed approach can be utilized to predict the electrochemical and physical properties of molten salts with arbitrary compositions and solutes, as well as the molten salt corrosion of metals.

In recent years, high-entropy alloys (HEAs) received great research interest due to their excellent performance. This study investigates the oxidation behavior of transition metal (TM) HEAs subjected to both static oxidation and cyclic oxidation under 900 and 1000 °C in the ambient atmosphere. Four HEAs are manufactured for the study. The oxidation kinetics, microstructures of oxidation products, and phases evolution under high-temperature oxidation conditions are studied in order to better understand the degradation of HEAs during oxidation. The results indicate the addition of Al has promoted alloy oxidation resistance by forming a protective oxide layer, and Cr element also contributes to this protective scale formation. The Ni2.1 eutectic alloy is shown to be the most oxidation resistant, followed by H4Cu10Al10, H4Cu15Al5, and H4Cu20. The excellent high-temperature performance of Ni2.1 in both static and cyclic conditions can be attributed to both protective scale formation and high stability due to the eutectic structure. Under cyclic conditions, alloys encounter severe oxidation owing to the enhancement of oxide growth and peeling, which leads to continuous oxidation of alloy at higher temperatures.

This paper examined the effect of surface preparation on the corrosion behaviour of copper coatings produced by electrodeposition and cold spray (CS) techniques. These methods are intended to be used to apply a copper coating on the used fuel containers as one of the multi-barrier layers to safely manage spent nuclear fuel long term in a deep geological repository (DGR). The as-received Cu samples exhibit significant variations in their surface chemistry and topography when compared to the polished samples. Furthermore, the microstructure and morphology of the CS coatings may not be homogeneous throughout their thickness. This study also examined the effect of polishing to different depths within the CS coatings on their resulting corrosion behaviour. To investigate the effect of surface preparation on the coatings’ corrosion properties, electrochemical measurements and complementary surface analysis techniques, such as Raman spectroscopy, X-ray micro-computed tomography (μ-CT), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), were employed. Consequently, it was observed that polishing the samples resulted in a more negative corrosion potential and an increase in corrosion current density, caused by the removal of the outer surface oxide layer formed during coating fabrication. However, there was no significant difference in the corrosion behaviour of Cu coatings and wrought Cu. Furthermore, despite the uneven distribution of voids and oxides throughout the CS coating, the corrosion properties were consistent. Therefore, it was concluded that polishing significantly changed the corrosion properties of as-received coatings, while the corrosion behaviour of the CS coating was almost homogenous through its depth.

The effect of hydrogen on thermally activated dislocation movement in high-strength martensitic steel with various amounts of hydrogen was studied using tensile tests and stress relaxation tests to clarify the role of hydrogen in the change of the mechanical properties. Oil-quenched JIS-SCM420 steel with a martensitic microstructure was prepared. After different amounts of hydrogen were introduced by electrochemical charging, tensile tests, and stress relaxation tests were conducted via in-situ hydrogen charging at 30 °C to evaluate the changes in both the nominal stress and the amount of stress relaxation compared with those for non-charged specimens. The resultant shear stress relaxation data were analyzed using nonlinear fitting curves to compare the apparent thermal activation volume of dislocation slipping with/without hydrogen charging. The change in nominal stress increased with increasing amount of hydrogen and was a maximum near the 0.2% proof stress regime. Meanwhile, the absolute value of stress relaxation decreased and the apparent thermal activation volume increased; these values were almost unchanged when the amount of hydrogen was more than 0.27 ppm. These results suggested that hydrogen acts as a barrier to dislocation slipping and causes hardening.

It is crucial to understand the degradation mechanisms of alloy Zr-2.5Nb, which is used for the pressure boundary in Canada Deuterium Uranium (CANDU®) reactors. In this study, Zr-2.5Nb coupons were exposed for 567 days at 325 °C with and without neutron-irradiation in simulated primary water chemistry. A combination of scanning/transmission electron microscopy and electron energy loss spectroscopy was used to investigate oxide layer chemistry and microstructure. The non-irradiated oxide layer exhibited equiaxed-columnar-equiaxed grains and interconnected nanopores, whereas the irradiated oxide showed a sporadic distribution of equiaxed-columnar grains and isolated nanopores. The nanopores may create pathways for the diffusion of hydrogen or ions through the oxide film. Nb oxidation state variation was correlated with nanopore density from the metal–oxide interface to the oxide–water interface; this likely resulted in a gradient in the oxygen concentration and electrochemical potential through the film. Subsequent micropillar compression tests on the oxide layer revealed subtle changes in the mean failure stress, whereas the mean failure strain remains the same for samples exposed for 1399 and 1750 days. Post-deformation characterization confirmed that the failure of the oxide layer is brittle and could be pseudo-shear, which is consistent with the critical failure mode for brittle materials and supported by finite element analysis. Further, TEM characterization confirmed transgranular cracking in the oxide layer during deformation.

The objective of this study was to explore the corrosion performance of major microstructures (including ferrite, pearlite, bainite, and martensite) presented in pipeline steels (in a simulated CO2-saturated aqueous phase). Commercially available carbon steels were transformed into monolithic single-phase samples through appropriate heat treatment for the corrosion study. The corrosion susceptibility of each produced microstructure was identified using potentiodynamic polarization measurements. The four microstructures exhibit noticeable differences of electrochemical behavior in the environment. At open circuit potential, pearlite exhibits the lowest corrosion rate, whereas ferrite has the highest corrosion rate. The preliminary results are discussed regarding the merit of this approach to advance the mechanistic understanding of how pipeline steels corroded in such a specific environment.

Protecting metal structures through organic coatings is vital to maintaining the integrity of metallic structures, particularly in the marine transportation industry. In response to the economic significance of marine transportation, there is a continuous research drive towards developing high-performance coatings that offer robust resistance to harsh marine environments. Achieving this goal necessitates employing advanced characterization methods, capable of swiftly and reliably assessing the protective performance of marine coatings. This study aimed to evaluate the feasibility of using an accelerated electrochemical technique (alternating current-direct current-alternating current (AC-DC-AC)) to simulate the degradation of marine primers. A comparative analysis of the AC-DC-AC technique and salt spray test was conducted to evaluate the delamination behavior of neat epoxy (NE), aluminum-pigmented epoxy (AE), and graphene-containing epoxy (GE) coatings. Electrochemical impedance spectroscopy (EIS) was used to monitor the degradation response of the protective properties of the coatings during the exposure to salt spray and the accelerated electrochemical test. The coatings subjected to the accelerated technique showed a similar degradation trend to those exposed to the salt-spray test, validating its reliability in assessing the delamination behavior of barrier coatings. However, the degradation rate was faster in the accelerated test. The graphene-containing coating provided a superior barrier performance compared to the aluminum-pigmented coating.

Stress corrosion cracking (SCC) of Ni- and Fe-based alloys in Pb-alkaline conditions is relevant to the degradation of steam generator tubing materials exposed to the extreme ends of plausible conditions of secondary side heat transfer crevices. Self-loaded U-bend samples of Alloys 600, 690, and 800 were exposed to 10 wt.% NaOH solution and 2 wt.% NaOH with the addition of 100 ppm Pb at 280 °C for 120 h to study the effect of Pb on the initiation of SCC in a mildly caustic environment. Post-exposure characterization was performed to evaluate dealloying susceptibility and investigate the role of Pb in impairing protective oxide films. Alloy 600 (Ni-16.10Cr-9.69Fe), Alloy 690 (Ni-29.80Cr-10.08Fe), and Alloy 800 (Fe-30.14Ni-20.25Cr) behaved differently due to chemical composition differences, notably Ni and Cr content. Alloys 600 and 800 were susceptible to Pb-induced SCC while all alloys studied were resistant to SCC in 10 wt.% NaOH without Pb.

With many moving parts, appropriate lubrication is vitally important in wind turbine operation. The Wind Energy Institute of Canada (WEICan) operates five 2 MW wind turbines. WEICan has observed issues such as foaming in their wind turbine gearbox oil and clogging of grease outlet chutes in their wind turbine generators. Both lubricant issues cause unexpected downtimes and may result in lost revenue, messy clean-ups, difficult troubleshooting, and are indicative of incorrect formulations, contamination, and/or degradation. Steps taken to address WEICan’s lubrication issues will be highlighted and potential root causes will be evaluated.

The objective of this work was to determine the effect of the Zn content on the corrosion susceptibility of dilute Al-Fe (Zn,Mg) alloy samples produced by a vacuum-assisted high-pressure die casting process. Corrosion susceptibility was assessed using an ASTM G85-A2 cyclic corrosion test with post-exposure mass loss and cross-sectional examination by scanning electron microscopy. Increasing Zn content reduced corrosion susceptibility by reducing the amount of primary Al attacked after the initial attack of the solute (Zn) enriched zone that forms adjacent to the grain boundaries.

The automotive industry is increasing its usage of Zn-coated press-hardened steels (PHS) in automotive safety and weight reduction applications, due to its ability to provide high strengths whilst also providing corrosion protection. However, there is some debate as to the fundamental corrosion mechanisms by which the mixed phase α-Fe(Zn) + Γ-Fe3Zn10 coatings provide cathodic protection. To this end, the objective of this research is to determine the fundamental mechanisms by which the mixed phase coatings provide cathodic protection, with an emphasis on the relative phase fractions of the Γ-Fe3Zn10 and α-Fe(Zn) phases in the coatings and their electrochemical characteristics. It was determined that small volume fractions of Γ-Fe3Zn10 in the coatings dominated the potentiodynamic characteristics of the coatings, indicated that this phase is essential in providing robust corrosion protection for Zn-coated PHS.

It is necessary to study the effects of all variables surrounding the preparation of magnesium due to its oxidative nature. This includes examining various cover gases during melting and casting. To minimize oxidation, the ability of different cover gases such as pure argon (Ar), Ar+R-134a, and Ar+R-1234yf refrigerants were tested on pure magnesium samples. The surfaces of the samples produced using different cover gases were examined using optical and scanning electron microscopy. EDS elemental analysis was conducted to obtain the composition of each sample surface. Oxidation was most effectively minimized under argon with refrigerant (R-134a or R-1234yf) cover gas combinations.

Even though cathodic protection is a common method of corrosion mitigation in many industries, there are some major problems and limitations associated with the way it is commonly applied. When used for the protection of marine vessels it only protects parts that are completely submerged in water, while it fails at protecting parts that are in intermittent contact with water or subject to humidity. It also does not adequately protect parts in the shadow of other parts or not facing the anodes. When used for the protection of steel structures that are in contact with water, which are often more complicated than marine vessels in terms of protection, common systems of cathodic protection are not as effective as desired. In such structures, there are buried parts, parts that are submerged in water, parts with intermittent contact with water (waves and tides), and elevated parts that are in contact with humid air and mist. Hence, in common cathodic protection systems, in which rigid anodes are placed out of reach of most parts of the cathode surfaces, the anodes cannot be present in the created electrolytes at most parts of the cathode. Conductive Coating ICCP (Impressed Current Cathodic Protection) Systems can overcome these problems by directly applying the anode on the surface of the cathode (substrate). This method will reduce the current required and therefore the power, eliminating the stray current corrosion, and simplifying the installation process thus reducing the overall cost of the system. However, this system suffers from some issues stemming from overprotection, during which hydrogen gas is released at the cathode. In many cases, this gas tends to diffuse and accumulate under the coating, causing blistering and eventually leading to what is known as filiform corrosion. A hydrogen-absorbent material is required to overcome this problem. This research will focus on determining the most suitable absorbent and catalyst materials as well as their proportions.

Thermally sprayed aluminum (TSA) serves as a protective barrier against both internal and external corrosion in a variety of hydrocarbon applications. Despite its efficacy, the degradation mechanisms of TSA, particularly in immersion scenarios and notably under thermal insulation, require comprehensive understanding. This study delves into the corrosion behavior of TSA using corrosion under insulation simulation setup, adhering to ASTM G189-07, and autoclave immersion. Corrosion tests, spanning three to four days under isothermal wet and cyclic wet conditions respectively, were augmented with linear polarization resistance tests to elucidate corrosion behaviors. The investigation involved meticulous microstructural examinations employing testing techniques such as confocal laser microscopy, detailed characterizations of microstructural features to comprehend 3D topography degradation, the utilization of scanning electron microscopy and energy dispersive spectroscopy. The findings revealed significant degradation of the TSA coating under insulation, attributed to the flashing of moisture and the active dissolution of iron at the insulation–metal interface. Unlike immersion conditions, the wear of TSA under thermal insulation resulted in crevices, fostering the active corrosion of the substrate steel. This nuanced exploration contributes to a more profound understanding of TSA’s behavior in complex environmental conditions.

Enhanced oil recovery operations involve the use of produced water with high salinity and dissolved CO2 gas, which can lead to aggressive corrosion in carbon steel pipelines. Experimental investigation into the corrosion properties of API X52 pipeline steel in CO2-saturated brine water environments reveal the influence of temperature, stress state, and salinity. Limited CO2 hydration directly affects the supply of protons which controls corrosion processes. Results from cyclic polarization tests indicate that temperature accelerates corrosion kinetics. Compressive U-bend samples exhibit lower corrosion penetration rates than tensile samples due to possible microstructural changes which require further surface analytical techniques for verification.

The present work examines the influence trace levels of air contamination (O2, H2O, etc.) have on the oxidation behavior of IN718 at elevated temperatures. IN718 specimens were heated to 1050 °C for 2 h in a TG equipped with three separate gas inputs: Pure He, He-0.219%Air (460 ppm O2)), and He-H2O (300 ppm) mixtures. The samples were characterized using TGA (mass gain/loss), GCMS (Contaminant pickup), and SEM-EDS (oxide morphology, thickness, and composition). Oxidation was shown to be governed by the atmospheric O2 and H2O content, on a mol-to-mol basis. The formation of discernable Cr2O3 and TiNbOx layers required a total O2 and H2O content of >100 ppm. Severe spalling of the Cr2O3 occurred at the highest concentrations of O2 assessed while the Cr2O3 layers formed as a result of H2O were much more adherent. The parabolic rate calculated from the TG results demonstrated a clear correlation between the oxide growth rate and contaminant concentration, which plateaued at the higher concentration, thus inferring rate limiting diffusion of oxide formers (Cr, Ti, Nb) with O2 and H2O, as the surface became depleted.

Harsh weather can erode the surface coating and protective layers of wind turbine blades, eventually affecting the structural integrity of the blades. Many types of leading edge protection (LEP) materials have been designed to help prevent the erosion of the blade edge. Since 2016, WEICan has carried out a field test of five different LEP materials. This field test provides an operational perspective on the effectiveness of different types of LEPs for wind turbine blades. We will discuss the surface preparation and application techniques required for the installation of each of the types of LEP and investigate observed issues, their causes, and their effects on performance and maintenance costs.

This paper presents a case study outlining the positive learnings from proactive corrosion design at a remote gold mine in Northern Canada. It was recognised from the design stage that many assets in the process plant would be exposed to high levels of salinity due to the water recycling process. One asset of concern was structural concrete as it was estimated that Ordinary Portland Cement (OPC) concrete would only last 4 years’ service life before the first damage (caused by rebar corrosion), particularly in the wet process locations. In 2017, the design team optimised the concrete mix design for durability over the life of mine (15 years) and included a concrete monitoring system to measure ongoing performance (consisting of reference electrodes and corrosion rate probes). The plant started operation in 2019. Over the past 5 years of operation, corrosion monitoring data have been collected, concrete cores have been used to determine chloride diffusion rates and concrete service life models have been populated. This paper provides an analysis of the assumptions made in design including a quantitative comparison of the impact of the selected option versus continuing with OPC. The paper will cover an assessment of the performance of the concrete (and risk) versus expectations, general costs and CO2 emission impact. Discussion will be presented on the scale of the benefits and the importance of including proactive corrosion considerations from the design stage of a project.

Within mining, structural assets are not always included as part of formal criticality or risk assessment processes during design. Beyond typical structural asset inspection (usually every 4–5 years) these assets are often overlooked when it comes to ongoing formal inspection and maintenance programs for other critical assets in the plant. However, mining exposures can be highly corrosive for structures and there have been documented collapses where corrosion has played a causal role. The level of corrosion severity is a function of many interrelated factors, reactive cultures, climate, proximity to the coast, quality of process water, chemical characteristics of the ore body, design material, and coating selection, etc. This paper will present case study-based experience with different sites to allow discussion of the trends in structural corrosion risk and will recommend a structured pathway forward based on corrosion management best practices.

Despite its proven better corrosion-resistant properties and higher critical chloride threshold than conventional carbon steel reinforcing bar (rebar), the high cost of stainless steel (SS) continues to be a barrier against its widespread use for reinforcing concrete structures exposed to marine and de-icing agents. With existing and emerging cost-effective but less corrosion-resistant or ‘unproven’ rebar alternatives, there exists a need to develop less costly SS rebar grades to encourage its widespread application. This development must begin with justification for the incorporation of the expensive alloying components in SS rebar, notably molybdenum and nickel that are rich in traditional austenitic and duplex grades like 316LN and 2205, respectively. Current results have shown that molybdenum-free austenitic 304L and duplex 2304 rebar counterparts provide sufficient corrosion resistance in chloride-contaminated concrete structures. Also, manganese, used to replace nickel in austenitic 24100 or duplex 2101, did not provide sufficient corrosion resistance as their nickel-containing 304L counterpart. The role of molybdenum, nickel and manganese in enhancing passive film and corrosion-resistant properties is discussed.

We investigated the impact of extended high-temperature and water exposure on fusion bonded epoxy (FBE) coatings applied to steel panels, commonly used in the oil and gas industry. We assessed the coating’s performance over an 85-week period at 65 °C in deionized water. Signs of degradation due to permeant sorption were evident within just 8 weeks. Cross-sectional analyses and focused ion beam milling revealed oxidation beneath the coating after 182 days, identifying the initial 200 days as critical for the onset of corrosion. This period likely signifies the beginning of the epoxy network’s breakdown and the establishment of a stable state of mass transport within the coating. Adhesion tests indicated a reduction in the coating’s pull-off strength due to water-induced plasticization, followed by a slight recovery attributed to secondary cross-linking. This research highlights the complexities in forecasting the failure times of epoxy coatings but provides vital data for constructing models to predict their lifespan under harsh conditions.

The objective of this work was to determine the in-situ correlation of the elemental dissolution of Zn with the potentiodynamic polarization in deaerated and naturally aerated 1 M Na2SO4 (aq). A custom-built in-situ atomic emission spectroelectrochemistry (AESEC) electrochemical flow cell, which incorporates an inductively coupled plasma-atomic emission spectrometer (ICP-AES), was used for this purpose. Major findings include (i) O2 reduction is the dominant cathode reaction, (ii) Zn spontaneously forms a slowly dissolving oxide corrosion product film and (iii) Zn dissolution occurs under cathode polarization in the presence of dissolved O2 reduction. Postexposure imaging shows the polarized surface is covered by a solid oxide corrosion product that consists of a porous outer layer residing on a compact inner layer.

This study investigates the chromia-forming Ni-based heat-resistant alloy UCX. The initial analysis of the as-cast microstructure, primarily comprising eutectic carbide and an austenitic matrix, also reveals various secondary phases and inclusions. Preliminary findings suggest that during an 8-h ramp-up from ambient temperature to 950 °C in flowing argon, the eutectic carbide dissolves and re-precipitates as needle-like secondary carbide. The thickness and morphology of oxides vary depending on whether they form above the previous eutectic carbide phase or the previous austenitic phase.

Refractory materials are subjected to significant chemical and mechanical loads, leading to their degradation and shortened lifespan. Erosion, driven by shearing forces originating from melt flow, stands as a primary mechanism for refractory wear. Despite its critical importance, a consensus on methods for quantifying refractory erosion is lacking. This study applies an inverse calculation method to investigate the erosion resistance of alumina coarse grain refractories in slags within the CaO-Al2O3-SiO2 (CAS) and CaO-Al2O3-SiO2-MgO (CASM) systems at temperatures of 1450 and 1500 °C. The method combines computational fluid dynamics (CFD) simulations with typical finger-test experiments. The CFD model resolves the slag-flow domain for which the refractory represents a dynamic boundary whose movement is governed by an erosion rate obtained based on an analogy to the field of soil erosion. An inverse calculation routine is utilized in the iterative solving of the non-linear least-square problem of parameter identification. The results demonstrate reasonable sensitivity of the calculated erosion parameters to slag composition and temperature. Higher values of detachment rate are obtained for slags in the CASM system due to the larger slag basicity. These values increase with increasing temperature. Correspondingly, the values of the critical shear stress are lower for the experiments with CASM slags and these decrease with increasing temperature.

Dealloying was detected in Monel 400 steam generator (SG) tubes in CANDU® reactors. We use Thermo-Kinetic E-pH diagrams (TK diagrams) to find likely conditions for dealloying of Monel 400 and Alloy 800. Subsequently, immersion tests were conducted under these conditions, to validate predictions and investigate the degradation mechanism. Monel 400 showed selective dissolution of nickel at pH = 6 at 85 °C, with the surface covered in redeposited Cu2O oxide. The dissolution of nickel in the form of acetate complexes appeared to initiate dealloying in Monel 400, leading to the formation of intergranular corrosion. On the other hand, no dealloying was observed in the Alloy 800 coupon under these conditions, attributed to the presence of a protective chromium oxide layer on the surface.

Corrosion studies in s-CO2-saturated aqueous systems draw less attention compared to wet s-CO2-rich systems. The current database cannot suffice the clarity for the effect of the aqueous component on the steel corrosion, e.g., the influence of Cl-ion on the dissociation of CO32− on the steel surface. In the present work, we explored the influence of Cl ion and temperature variations on the corrosion of X65 steel in supercritical CO2 (s-CO2) saturated aqueous environments. Corrosion experiments were conducted on X65 steel in s-CO2-saturated 3.5 wt.% NaCl solutions at 8 MPa with varying temperatures of 50, 75, and 100 °C. X65 steel exhibits significantly lower CRs in s-CO2 saturated salt (NaCl-containing) aqueous solution compared to those in DI water. After exposure to s-CO2 saturated DI water at 50 °C for 96 hours, a loose and cracked FeCO3 film was observed on the X65 steel, resulting in the highest CR of 5.10 mm/y, in contrast to the samples exposed to the s-CO2 saturated salt solution at 50 °C (1.47 mm/y), 75 °C (1.01 mm/y), and 100 °C (0.93 mm/y).

This work developed an accelerated bulk immersion surrogate that reproduces the corrosion mode and extent exhibited by secondary A356-T6 (AlSi7Mg0.3) Al alloy samples made by the low-pressure die castings process after 1000 h of ASTM B117 continuous salt fog exposure. The accelerated test will be used to determine the effect of pre-corrosion on the uniaxial tensile properties including strength and ductility (elongation) in an expedited manner. The corrosion mode exhibited after 1000 h of ASTM B117 exposure was interdendritic with the eutectic Al phase serving as the anode and the eutectic Si phase serving as the cathode and without any significant attack of the primary Al matrix. Of the various bulk immersion surrogates tested (with and without electrochemical polarization), the one involving 96 h of bulk immersion in 5% NaCl (aq) + an initial addition of 30% H2O2 (aq) (9 mL in 1000 mL) at 35 °C under open-circuit conditions was most successful.

Steam generator tubing used in the Pickering Nuclear Plant is comprised of Monel 400, a Ni-Cu alloy. In 2016, five tubes excavated from unit 4 of Pickering exhibited intergranular attack and dealloying of nickel on their outer diameter. Open circuit and potentiostatic corrosion experiments were conducted to evaluate the corrosion performance of commercially available Monel 400 and model Ni-Cu alloys in simulated steam generator environments. It was found that Monel 400 will undergo dealloying in occluded regions, where Cu2+ can accumulate to sufficient concentration that stabilizes elemental copper. Characterization by electron microscopy revealed the presence of Ni3B at Monel 400 grain boundaries which was proposed to be the cause of intergranular attack in this material. Gas chromatography and potentiodynamic polarization were carried out to evaluate the inhibiting effect of HCOO− which occurs at an open circuit.

In modern industries such as marine, the rising costs from corrosion attacks are a significant challenge. Additive Manufacturing (AM) stands out for crafting intricate components with unique geometries. The inherent high cooling rates and nonequilibrium solidification conditions in AM lead to distinct microstructures, potentially resulting in varied properties compared to conventionally manufactured components. Understanding the correlation between AM-induced microstructures and the corrosion properties is crucial. Initial exploration focused on CX stainless steel (CX SS), fabricated through laser powder bed fusion. Subsequent studies evaluated the impact of heat treatment on CX SS components, comparing their corrosion behavior to wrought AISI 420-SS. Scrutiny extended to the electrochemical behavior of an interface between CX SS and wrought AISI 420 SS. Finally, nickel aluminum bronzes (NAB) fabricated via wire arc additive manufacturing were examined for their corrosion performance in as-built and heat-treated conditions, particularly relevant for biofouling resistance in marine and shipbuilding applications. Electrochemical tests, as well as microstructural characterization methods, revealed that the AM as-built CX SS exhibited superior corrosion resistance compared to conventionally manufactured martensitic stainless steel. Moreover, the anisotropic features developed during the AM process resulted in slight differences in corrosion behavior between the two sides of the AM CX SS samples. Furthermore, it was observed that hybrid samples of CX SS-420 SS showed higher corrosion resistance in the as-built state compared to their counterparts in the heat-treated condition. Additionally, the as-built WAAM NAB samples demonstrated higher corrosion resistance in the as-built state than those that underwent heat treatment.

Nickel aluminum bronze (NAB) alloys are widely recognized for their promising corrosion characteristics, making them prime candidates for harsh environments. The use of laser-powder bed fusion (L-PBF) additive manufacturing process has been on the rise for the production of highly intricate NAB components. Nonetheless, the impact of building direction on the corrosion characteristics of L-PBF fabricated NABs remains unexplored. This study investigates the impact of building direction on the electrochemical corrosion characteristics of L-PBF UNS C63020 NAB in a 3.5 wt.% NaCl environment. The microstructural characteristics are scrutinized using optical microscopy (OM) and electron backscatter diffraction. Electrochemical performance assessment of NAB is conducted through various electrochemical techniques, including electrochemical impedance spectroscopy (EIS) and cyclic potentiodynamic polarization (CPP) methods. This study aims to establish the correlation between microstructural homogeneity, specifically the fractions and distribution of phases/micro-constituents within NAB, and its corresponding electrochemical behavior. Through this investigation, we seek to elucidate the tendency of NAB alloy towards either isotropic or anisotropic corrosion response.

Today there are several successful case histories demonstrating the suitability and long service life of fiber-reinforced polymer, FRP, based equipment in hydrometallurgical extraction plants used to refine copper, nickel, cobalt, and rare earth metals. FRP is being considered as a material of choice for the construction of lithium extraction systems from geothermal water or other traditional sources. The chemical environments found in modern extraction systems are extremely corrosive. These systems must be fabricated from materials that are durable against corrosion, meet mechanical requirements, and perform economically over the life of the plant. In these systems, FRP provides improved durability relative to alternative materials of construction. This paper will compare the corrosion performance of plant equipment fabricated with corrosion-resistant alloys, rubber-lined steel, and FRP made with epoxy vinyl ester thermoset resins. Case histories for FRP piping, storage tanks, extraction vessels, and electrowinning cells combined with laboratory-based corrosion studies will be reviewed to demonstrate how FRP materials are selected for hydrometallurgical equipment. Data showing the suitability of FRP for lithium extraction will also be reviewed.

Hydrometallurgical processes necessitate robust materials capable of withstanding corrosive environments. This study evaluates the corrosion behavior of 2205 duplex stainless steel (DSS) using a two-level factorial design in simulated hydrometallurgical conditions. Factors including sulfuric acid concentration, Fe(III)/Fe(II) ratio, copper concentration, and temperature are investigated for their impact on the uniform corrosion rate of the alloy. Temperature, Fe(III)/Fe(II) ratio, and sulfuric acid concentration are individually significant for corrosion rates. The temperature/sulfuric acid and Fe(III)/Fe(II) ratio/temperature interactions were also found to be significant. Despite the various aggressive conditions, 2205 DSS had corrosion rates below 0.1 mm/year. Moreover, the alloy exhibits robust resistance to localized corrosion with critical pitting and crevice corrosion temperatures exceeding 95 °C, suggesting its suitability for hydrometallurgical applications.

Vehicle lightweighting has been a key driver for vehicle manufacturers to reduce the carbon emission of the internal combustion engine and to increase the range of electric vehicles (Joost and Krajewski, Scr Mater 128:107–112, 2017). Mg alloys are one of the competitors in automotive applications (Shi et al. Sci Rep 10:10044, 2020; Luo et al. JOM 73:1403–1418, 2021). The objective of this work was to determine the corrosion susceptibility of three Mg alloy extrusions in NaCl (aq) and the role played by the major alloying elements. Alloys under study include AM30 (Mg-3Al-0.4Mn), ZE20 (Mg-2.4Zn-0.2Ce), and ZAEXM11000 (Mg-1Zn-1Al-0.2Ce-0.2Ca-0.4Mn). Cross-sectional examination of the extruded microstructures using microscopy techniques revealed two distinct metallurgical zones: (i) recrystallized coarse-grained skin layer and (ii) an uncrystallized fine-grained core. The relative corrosion susceptibility of each zone, as a starting surface, was investigated using potentiodynamic polarization and volumetric H2 gas evolution as a function of immersion time in 0.1 M NaCl (aq).

There has been a growing interest in modelling the material degradation and transport mechanisms that lead to elevated radiation fields in the primary heat transport system (PHTS) of nuclear reactors. Meanwhile, online monitoring for flow accelerated corrosion (FAC) could have significant impacts on station FAC management programs providing real-time corrosion rate information. The Corrosion and Radioactivity Transport Analysis (CARTA) code has been under development at UNB since 1996 and is a one-dimensional, comprehensive simulation package that mechanistically unifies the various material and activity transport processes in a typical, 600 MWe Canada Deuterium Uranium (CANDU-6) nuclear reactor. The output of the object-oriented code includes flow-accelerated corrosion (FAC) rate and active and inactive elemental composition in the coolant and circulating crud. CARTA is adaptive to changes in materials of construction and incorporates kinetics, mass transfer, material wear, and a detailed boiler thermal-hydraulic model, which has been benchmarked to station data. The concept of hydrogen flux monitoring for assessment of FAC in CANDU reactors was validated at the Canadian Nuclear Laboratories and the commercial application was developed at the CNER, with the first successful deployment at the Point Lepreau Nuclear Generating Station (PLNGS) in 2006. Operation of Hydrogen Effusion Probe (HEPro™) both pre- and post-refurbishment at PLNGS has demonstrated the viability of measuring the FAC rate on outlet feeders, in-situ and in real-time, which has been incorporated into the CARTA code. This paper presents material and activity transport simulations for a typical CANDU-6 reactor, including post-station refurbishment and the capability of the HEPro is highlighted.

The rotating cylinder Hull cell was used to plate deposits from industrial electrorefining electrolyte samples, and different factors related to nodule formation were examined. Excessive glue concentration was shown to initiate nodulation. Insufficient glue resulted in lacy deposits at low current densities (<200 A/m2). The effect of current density varied, but in general, a current density above 300 A/m2 was required to cause nodules, and this was attributed to mass transfer limitations. Nodulation formed below 300 A/m2 is likely due to suspended slime particles in the electrolyte. Changing glue or thiourea concentrations were not effective in treating nodulation caused by slime particles.

We exclude metals whose reduction is thermodynamically favored over hydrogen evolution in acidic solutions and focus on non-noble metals. Historically, the development of these processes was slow in comparison to those of metals like copper or gold. For nickel, avoidance of buildup of stress in the deposit was a significant issue. For zinc, current efficiency slumps and stripping problems were common in the early years of the development and operation of commercial processes. Important factors in the optimization of electrowinning processes for non-noble metals can be summarized as housekeeping issues, adequate electrolyte purity and current density, plating overpotential and its sensitivity to deleterious impurities, nucleation overpotential, electrolyte conductivity, and viscosity, supply of the cation to be reduced, and chemical factors which may be specific to the application. In highly acidic electrolytes, limiting current density may become a non-issue. For the ongoing development of processes in conventional parallel plate cells, including the introduction of alternative anodes, it will be important to consider each of these factors. A set of tools for measurement of important electrochemical and other physico-chemical and engineering parameters is suggested and discussed. We provide illustrations drawn from the literature and from the experience of the senior author for electrowinning of zinc or other non-noble metals.

This paper deals with Metso’s Outotec Silver Electrorefining Process (Ag-ER) of Pd-rich Ag-anodes at high current density (HCD). Several Ag-ER tests with anodes containing up to 2% palladium were performed at anodic current density of 800–1200 A/m2. Apart from current density, the effects of other parameters, such as pH, temperature, and electrolyte flowrate, were studied to minimize palladium deportment to the refined silver. Thermodynamic calculations of the speciation of oxidized palladium in the electrolyte during Ag-ER were carried out. A major part of the oxidized palladium reports to silver anode slime as low-soluble hydroxide or oxide.

This work presents a novel metal-air desalination battery (MADB) capable of treating solutions of varying salinities. MADBs typically consist of an anode and a cathode compartment, separated by ion-exchange membranes. Desalination of the feed water occurs due to electrochemical reactions taking place at the anolyte and catholyte compartments. Zinc was selected as the anode due to its high specific energy density and low cost. Key performance parameters were evaluated including feed water concentration, salt rejection, salt removal rate, and charge efficiency. The Zn-air desalination battery developed in this work showed promising desalination capabilities and it is expected to contribute to the further development of energy-efficient desalination technologies to addressing the global water demand.

Magnesium hydroxide (MH), as a potential alkalinity source, is one of the most promising materials for permanent carbon dioxide removal (CDR) via ocean alkalinity enhancement. We present a new method for generating MH in a diaphragm/membrane-separated electrolyzer using magnesium sulfate as a catholyte and sulfuric acid as an anolyte. This approach offers a zero-waste production of MH of desired purity while generating sulfuric acid, hydrogen, and oxygen, concurrently. The acid is used to extract the Mg from mineral deposits as magnesium salt containing leach solution. Hydrogen can be used as a fuel and subsequently oxidized either by combustion or in a fuel cell to regenerate water and release energy. The oxygen can be vented to the atmosphere or used in solution processing and other mining operations. We designed the unit cells for MH production on an evolving basis, with a view to certain operational challenges. The sources of voltage increase on the cell such as accumulation of MH in a system and adhesion of MH deposits on cathodes were addressed by the cathode vibration technique. The diaphragm-divided cell achieved over 90% current efficiency (C.E.) based on MH at the expense of losing the Mg in anolyte. An anion-exchange membrane divided cell minimized the transport of Mg into anolyte, but the C.E/ never exceeded 70–80% C.E. MH. The preoptimized outcome from unit cells was the energy consumption ranging from 4.9 to 6.5 MWh/t MH. The unit cell performance was validated in the scaled-up version of one of the cells to the multi-cell containing five cathodes and four anodes. We tested two process solutions. The first consisted of a magnesium sulfate with certain impurities (manganese, nickel, calcium, and sodium) simulating the process solution of waste asbestos mine tailings. The second test solution originated from an actual nickel laterite operation. The electrolysis was conducted in three stages. The product of the first stage of electrolysis precipitated most of the impurities along with MH. This product can be used for mixed metal hydroxide precipitation circuit (MHP) practiced in nickel laterite and similar operations. The extent of MH precipitation in the first stage of electrolysis was controlled by the applied current. The final stage of electrolysis produced the MH of the desired purity (over 85% MH) suitable for ocean-based CDR. Based on results from the multi-electrode cell studies, a cell stack configuration and electrical system requirements for constructing industrial-scale electrolytic system for MH production were developed. The calculation was based on process solution inflow rate of ~70 L/min and input Mg content of 47 g/L. The modeling outcome indicated that over 2.7 t/year of MH can be generated efficiently and with a specific energy consumption not exceeding 6 MWh/t-MH.

Primary iron metal is produced through the CO2-intensive carbothermic reduction of iron oxides in blast furnaces. Since carbon is used as both a reducing agent and fuel for the process, blast furnace pig iron cannot eliminate its CO2 emissions. Therefore, in recent years, carbon-free electrochemical processes fed by renewable electricity have been investigated as potential green alternative routes for iron production paving the way for a net zero economy. The most important European initiative in this direction was the SIDERWIN project. This paper deals with the fundamentals of iron production with the SIDERWIN approach and presents the results of iron production utilizing as potential raw materials either Bauxite Residue or the cinder from the reductive, with hydrogen, soda roasting of Bauxite residue.

This study investigates the capability of electrochemical techniques for the production of metal oxide materials from hydrometallurgical process solutions by deposition on an electrode surface. Morphology and deposited material composition are characterized by different techniques including SEM-EDX and cyclic voltammetry. Additionally, the influence of potential, temperature, manganese concentration, and pH on the process are examined.

The electrochemical aqueous reduction (EAR) method is studied for the recovery of precious metals from solutions typical in hydrometallurgy. In the first step, multivalent metal ions are reduced after which they spontaneously react with precious metal ions also present in the solution, resulting in the deposition on the electrode. The EAR mechanism and the deposit composition and morphology are studied with cyclic voltammetry, electrochemical quartz microbalance, and SEM-EDX. The results show that homogenously distributed Au or Pt nanoparticles can be deposited on the glassy carbon, ready for use in applications like catalysis.

Maintaining certain concentrations of thiourea, glue, and chloride ions in the electrolytic solution is necessary to promote efficient and homogenous copper deposition in electrorefining. Over the past year, new practices have been implemented and standardized at the Rio Tinto Kennecott (RTK) Refinery to improve the control of these concentrations within these set limits. Through a better understanding of plant processes, greater interdepartmental collaboration, and consistent daily checks, improvement was observed. Average current efficiency increased and varied less in the face of condition changes such as outside temperatures, varying pull cycles, and use of slightly out-of-spec anodes.

Low-temperature electrolysis of iron ores is a novel technology aimed at reducing the environmental impact of current iron-making that is responsible for heavy CO2 emissions. This technology under development by ArcelorMittal involves the electrolysis of an iron oxide ore suspension in a hot (110 °C) caustic (50 wt.% NaOH) solution at a high current density (1000 A/m2). Research conducted at McGill under the sponsorship of ArcelorMittal is seeking to understand the effect of various iron ore properties (mineralogy, impurities) and electrolytic process parameters (temperature, caustic concentration, suspension conditions, electrode configuration, voltage range, and mode, etc.). Tests are carried out in batch and continuous benchtop electrolysis setup and reacting iron oxide particles as well as the metallic iron deposit are characterized to determine transformation and deposition mechanisms. In this chapter, we aim to present some recent results obtained at less severe conditions, namely reduced T (50 °C down from 110 °C), and NaOH concentration (30% down from 50%) using synthetic hematite. In this project, the electrolysis time, initially set at 6 hours, has been extended to 24, 48, and 72 hours. These extended electrolysis periods provide new insight about the dynamics of the process both in terms of current efficiency (time-dependent electrode polarization), oxide reduction evolution, and metal deposit growth.

There is growing need for production of green hydrogen as we intensify our efforts to reduce our dependency on fossil fuels. Water electrolysis remains however an expensive technology with a lot of research applied to development of low cost electrocatalysts. Photocatalysis could become an avenue towards green hydrogen production either via direct splitting of water or in conjunction with electrolysis (photo-assisted). Herein, we evaluate BiVO4 as photocatalyst to reduce the overpotential of oxygen evolution hence reduce the overall power requirement for water splitting. In particular, we propose a few different approaches to improve the performance of BiVO4 photoanodes, based on the use of heterostructures and co-catalysts, to better suit potential future applications. The optimization of photoanode materials, such as BiVO4, is indeed a crucial aspect toward an efficient solar-to-hydrogen conversion. On these premises, PEC water splitting can certainly be a competitive approach to sustainably produce hydrogen for next-generation energy conversion.

Manganese removal is an essential step for implementing MMO anodes in zinc electrowinning. We worked on the manganese removal process using an SO2/air gas mixture. Our results indicate that copper as a catalyst has a detrimental effect on manganese removal at high concentrations, and MeOH suppresses the manganese elimination and reduces the solution potential from 750 to 703 mV.

Copper electrorefineries operating with high nickel concentrations have reported that the presence of Ni2+ has led to increased nodulation as well as decreasing current efficiency and increased frequency of dendrite growth. High nickel concentrations may also promote passivation and affect the forming of the slime layer and thus indirectly negatively influence the cathode quality and contamination. This chapter summarizes the recent experimental observations that researchers at Aalto University have made regarding the behavior of nickel in copper electrorefining. Nickel contamination has been mainly attributed to contamination caused by anode slime; however, the electrolyte inclusions have also been found to possibly occur with the potential for major nickel contamination. In recent studies, nickel-containing particles have not been directly linked to nodulation nor does nickel have a significant impact on the cathode roughness, but nickel has been found to influence the formation of slime layer and thus indirectly causing cathode contamination.

Zinc electrowinning faces challenges due to high power consumption from conventional lead-based anodes. Mixed metal oxide anodes offer a solution but are hindered by manganese ions in zinc electrolytes. This study explores a manganese removal strategy utilizing plant off-gas rich in SO2 with cobalt as a catalyst to address this issue. Real industrial solutions from CEZinc were tested, showing a remarkable reduction in manganese levels from 4500 to 10 mg/L within 120 minutes. However, the unintended removal of cobalt and other impurities underscores the necessity for an optimized purification strategy.

An approach to reducing the carbon footprint of an electrowinning process is a complete redesign of the cell, with or without altering the anode process. We will review some of the concepts found in the literature for cell design along with their economic promise. Some candidates are rotating drum cells, spouted (or falling packed) bed cells, EMEW cells, and hydrocyclone cells. All kinds of metals can be considered here: base metals including copper, precious metals—gold, silver, and platinum group metals of rows 5–6—and rare earth metals. Proof of any such technology at plant scale may need a medium to large volume but relatively high value metal. A by-product may be a good candidate. By and large, all the factors delineated in our other paper at this symposium outside of the one dependent on a parallel plate electrode geometry are likely to remain important, with some exceptions for precious metals and copper. A change in cell geometry might be modeled via a change in Wark’s constant. Although proton-blocking anion exchange membranes showed some promise for spouted bed electrowinning, based on technical risk, it is probably better to decouple a membrane process for the separation of acid and salt from the electrowinning process. With this contribution, we aim to attract a new generation of metallurgists to this field and to inspire a consortium to support the development and piloting of advanced concepts on suitable candidate metals.

Unlike conventional cementation processes, we utilized a novel electro-assisted cementation (EAC) process to improve Cd removal from Zn processing wastewater. Additionally, we investigated Cu recovery from Cu smelting flue dust (CSFD) leachate using the same EAC process. Leveraging electrochemical principles, the EAC process improves metal recovery efficiency. Under optimized conditions, we achieved 98.5% recovery of dissolved Cd at 94.1% purity. Similarly, EAC enabled 98.2% removal of Cu from CSFD leachate.

Electrochemistry plays an essential role in modern technologies of energy conversion, metals production/recovery, and corrosion-resistant materials. A proper control of electrode reactions in a complex environment is an important consideration for the successful development of future sustainable electrochemical technologies. Today, rare-earth metals are produced by electrolytic reduction in molten salts and play a critical role for the transition to a green, low-carbon economy because of their essential role in renewable energy technologies such as permanent magnet (NdFeB) motors for electric vehicles and wind turbines. This presentation will discuss electrochemical processes for rare-earth alloys (e.g., Nd-Bi and Nd-Fe) in molten salts with a specific focus on fundamental challenges of rare-earth electrochemistry (e.g., high reactivity and multivalent states) that can lead to low process yield. As a first step to understanding electrode processes of rare-earth alloys in molten salts, thermochemical properties of rare-earth alloys (e.g., Nd-Bi and Nd-Fe) were investigated via electromotive force (emf) measurements in complement with characterization of alloy electrodes via thermal and microstructural analyses. Based on the emf of these alloys, the electrochemical formation of these alloys is demonstrated in molten salts with an estimation of the process efficiency.

In copper electrodeposition, bone glue is commonly used as a leveling agent to inhibit the growth of nodular copper deposits. However, glue is degraded through hydrolysis due to the high acid concentrations and temperatures of industrial electrolytes. This study uses atomic force microscopy (AFM) and scaling analysis to monitor the influence of glue degradation on the roughness of small-scale and short-term copper electrodeposits on 316L stainless steel. The electrolyte contained 3 mg/L of bone glue and was maintained at either 40 or 60 °C, while a series of 10-min copper deposits were collected with varying electrolyte age. Images of the surfaces were captured using AFM from which the root-mean-squared (rms) roughness (δ) was extracted. Results show that copper deposits were initially rough, but became smoother as glue became active in the electrolyte. This was followed by a nonlinear increase in surface roughness and attributed to the conversion of active glue into degraded glue as electrolyte age increased. The data was fit to a kinetic model to extract the rate constants for the conversion of inactive glue (I) to active glue (A) and then to degraded glue (D). Elevated temperatures not only increased the rate of active glue production but also the rate of degradation. Further experiments used 10-, 12-, 14-, and 16-min deposits to determine the influence of deposition time on roughness and to predict surface morphology using scaling analysis. The final kinetic model using a modified scaling approach accounts for the effects of both glue degradation and deposition time on copper deposit roughness.

Insoluble, iridium MMO-coated titanium anodes were first developed in the 1970s and are now used in a variety of applications, including metal electroplating. However due to the high costs associated with the iridium precursor and the sensitivity to corrosion by chlorides, the practical applications so far are limited. A new, recoverable iridium MMO coating has been developed for use in metal recovery with reduced sensitivity to chlorides. The development of this coating as well as practical results achieved in the recovery of metals present in waste streams are presented.

The world is going towards electrification faster than ever in many fields including transportation and automotive fields such as buses, heavy trucks, and machinery too. However, in other fields, the rate of electrification is still somewhat slower. For example, one specific field is the precious metals (PM) refining industry, which is very much needed for the green transition and hydrogen economy. The PM industry is nowadays heavily relying on chemical-intensive processes and electrowinning is used to recover already purified solutions. As electrification is evident, the PM industry should not differ relative to other fields driven by electrification. The current electricity-driven processes are designed to operate with well-specified solutions, prior operation steps are required. The energy intensity of those processes is huge and their chemical load is even higher. Usually, the chemical-intensive process is divided into smaller unit operations, where similar chemicals relying on the operation are repeated just to get certain elements below their threshold values in order to get the best out of the EW process. One possibility is the use of well-tailored, pulsating-based electrolysis provided by Elmery Ltd., which is based on a patented unique metal recovery technology for refineries to better circulate the metals, increasing cost-efficiency and sustainability.

Mechanical vapor recompression (MVR) and electrodialysis (ED) are very energy-efficient electrotechnologies to recover valuable products from dilute waste streams into concentrated products. MVR can concentrate streams with much less energy than conventional evaporation. ED can also be used for concentrating products, plus extracting and separating products, purifying solutions, and regenerating salts into their base and acid which could be concentrated further by MVR. There are several competing and complementary technologies to MVR. Their energy consumptions are compared, and some MVR case studies are presented. ED applications are numerous as well, but salt splitting is of particular interest.

While the primary ore for iron and steel production is based on oxide minerals, which can be used as a feedstock for electrolysis and production of iron metal and oxygen gas, iron sulfide as a feedstock offers an opportunity for electrolysis in molten sulfides. Using sulfur- and sulfide-based chemistry for the preparation of iron sulfide and for electrolysis is promising for the mitigation of GHG emissions, yet, to date, the features of a molten sulfide electrolysis process for iron have not been reported. Herein, we present some of the key background work that supports the features of iron production by molten sulfide electrolysis.

While Canada’s Critical Minerals Strategy focuses on the mineral extraction, processing, advanced manufacturing, and recycling of such metals and materials, the contribution of chemicals used in those processes to net-zero calculations and the waste generated are to be addressed. As part of objective two of the strategy, the waste reduction innovative technologies, and processing techniques can also lift part of the GHG emissions, enhance process circularity, and augment autonomy through onsite recycling. One such innovative technology and processing technique is the use of electrodialysis processes. The electrodialysis processes could, by using electricity, recover spent acids/caustic used in processes, separate waste such as sodium sulfate into sulfuric acid and caustic soda to be used back into the generating processes, and be transformed into acid-base flow batteries to store excess electricity production on remote locations. Some problems were addressed. First of all, membrane technologies in such processes suffer from high concentrations (high osmotic pressures) achieved in the lixiviates. This high osmosis pressure causes the transfer of cations through anionic membranes and anions through cationic membranes, causing contamination. Another example is that membranes chosen for their permeation selectivity can improve or decrease the whole cell voltage. For instance, there is less contamination with thicker membranes, but this makes the resistivity of the whole cell higher, increasing energy demands. This presentation surveys technologies that have the potential to lower energy consumption in the electrodialysis process, hence greatly lowering GHG emissions and decreasing contamination problems, while limiting waste production.

We tested licorice concentrations ranging from 25 to 100 ppm in a simulated copper electrowinning (Cu-EW) solution for acid mist suppression efficiency. Current densities between 280 and 380 A/m2 were tested. We also examined the influence of licorice addition on other operational parameters, including current efficiency, cell potential, and energy consumption. Introducing licorice into the Cu-EW solution had a negligible impact on current efficiency, which remained above 98%. With licorice concentrations above 50 ppm, we achieved an acid mist suppression efficiency exceeding 99%. Regardless of the applied current density, 100 ppm of licorice formed a foam layer of about 3.5 cm on the surface of the electrolyte, which acted as a barrier against acid mist release.

Electrical energy is the largest operational expense in electrowinning and directly impacts the cost of copper production. To understand the contribution of cathodes in the power consumption of electrowinning, a two-part methodology is proposed measuring the cathode conductivity followed by measuring the specific energy consumption of the cathode. The conductivity of the cathodes was measured by a type of 4-point probe conductivity methodology. The conductivity results will be presented via a conductivity map grid produced from grid measurements. Correlation of measured cathode conductivity to electrowinning performance will be evaluated against the specific energy of plated copper. The specific energy of electrowon copper was evaluated under constant current conditions by cathode to (1) understand geometric and current density effects and (2) by constant surface area to minimize current density effects. In this manner, the performance of copper cathodes regarding energy consumption may be compared across copper electrowinning cathodes. It is anticipated that this methodology and findings will assist the practitioner in evaluating key cost components in their electrowinning operations.

In copper electrowinning (Cu-EW) process, lead alloy anodes have been the widespread reference for oxygen evolution reaction (OER). On the other hand, Mixed Metal Oxide anodes (titanium substrate plus coating for OER) are considered as an alternative enabling power saving and removal of lead sludges and eliminating the need for cobalt addition. Normally, Cu-EW solution contains mainly copper sulfate and sulfuric acid, and durability and activity are required to anodes. In this context, De Nora has been working on development of a coating for MMO anodes for Cu-EW and verified a multi-year operation under laboratory test using a real plant solution. A developed coating was integrated into De Nora DSA® Self-protective Anode, which can withstand short circuit conditions with no damage to the anode by limiting the current flow on the short circuit. De Nora DSA® Self-protective anodes have been supplied to electrowinning plants for operation in Cu-EW customers’ conditions for industrial testing and validation, and successful operation for more than 50 months has been confirmed at a specific customer.

Lead-based alloys are the primary anodes used in electrowinning from sulphate-based aqueous systems. Lead anode technology has evolved over the years, migrating from pure lead and lead-antimonial alloys to the currently used lead–calcium–tin alloys for copper electrowinning, and lead-silver alloys for zinc electrowinning. It has also migrated from cast to rolled microstructures in search of improved mechanical properties and higher corrosion resistance. Although great strides have been made in the development of new alloys and production processes, the industry still has unresolved issues related to untimely corrosion, which limits anode life and may lead to higher contaminant levels in the metal being produced. Lead anodes corrode because of the difference in the chemical/electrochemical potential across the microstructural features of an anode. Given a very high-purity material, we find that the grain boundary areas corrode significantly faster than the rest of the grain. The desire to minimize grain boundary corrosion by a balance of alloying element selection, and microstructural design allows the grain boundary area to be engineered. However, operational issues can lead to unexpected corrosion behaviours, which we will discuss moving forward. The examples in this work, though directed towards copper electrowinning, can be extended to similar phenomena in other metals electrowon from sulphate media (i.e. zinc, nickel, cobalt, and manganese). The lifecycle of electrowinning anodes is dependent upon electrowinning tank house operating conditions and maintenance of the anodes, including cleaning and straightening. This paper will focus on the operational aspects of maximizing the utilization of lead electrowinning anodes.

Carburization is a critical aspect of the iron and steel industry as it can affect the mechanical and chemical properties of the end product. The purpose of the current paper is to provide a comprehensive analysis of the carburizing potential of high-grade iron ore pellets after direct reduction in pure hydrogen. The results show that the porosity in the pellets has a significant impact on the efficiency and success of the hydrogen direct reduction process. In addition, the reduction process could be brought to completion at a lower temperature compared to carbon monoxide; however, in the presence of pure hydrogen, iron carbide reaches its peak equilibrium concentration at temperatures up to 500 °C, subsequently decreasing with further temperature increments. The uniform dispersion of SiO2, Al2O3, and CaO was crucial in the carburization process, affecting the ultimate properties of the steel. The heightened metallization degree and augmented porosity were associated with improved carburization tendencies. This correlation underscores the intricate interplay between temperature, carbon sources, and the resultant equilibrium concentration of iron carbides, shedding light on the nuanced dynamics of this phenomenon.

The two twin-electrode DC furnaces at Koniambo Nickel SAS (KNS) have suffered from a loss of arc (LOA) problem since commissioning. LOA manifests itself by the sudden extinguishing of the electric arc between the electrode tip and slag bath. LOA occurred randomly with no clear correlation to process parameters. Lost power from LOA led to large fluctuations of the power-to-feed ratio in the furnace. The inability to run at stable high power and frequent stoppages to correct power-to-feed imbalances were the main barriers to achieving the nominal furnace design production rate. Heuristic process levers were developed to reduce the occurrence of LOA. None showed systematic and reproducible benefits to LOA reduction, and the root cause remained unknown. Bench scale tests were run that clearly and reproducibly showed the events leading up to LOA. These events are explained using electromagnetic theory. The LOA problem was solved by reversing the polarity of one electrode, which converts the attractive force experienced by the arcs into a repulsive force. Both furnaces were converted to this new configuration by the physical rotation of the rectifier thyristors of one electrode. Following the change, LOA frequency was drastically reduced. Furnace power setpoints above 100 MW are now readily achieved with no need for constant process parameter adjustments. The increased electric stability has led to increased process stability with no negative consequences to furnace integrity.

The treatment of fly ashes from waste to energy (WtE) power plants is necessary due to the increasing cost of landfilling. Their use as a supplementary cementitious material (SCM) is a promising alternative. However, a treatment process is required to remove the chlorides, sulphates and heavy metals such as zinc and lead. A two-step process is proposed in which water washing removes the chlorides from an initial content of 16 to 1 wt%. The fly ash and water are mixed at an s/l ratio of 1:5 and heated to 60 °C for 1 h. The filtered material is then dried, combined with 18 wt% of sand (silica source), and heated to 1300 °C in a top submerged lance (TSL) reactor. Sulphur is removed through a reaction with silica. The heavy metals are then removed by reaction with the remaining chlorides and by means of the atmosphere generated by excess fuel addition in a reductive step in the same reactor. The final product has a composition similar to blast furnace slag and can be utilised as an SCM.

In the last two decades, nickel has become an important issue due to escalating demand from various industries such as stainless steel, non-ferrous alloys, plating, casting and especially batteries with compound annual growth rate (CAGR) of about 8% from 2015 to 2040. Nickel is the fifth most abundant element in the world, which is originated from magmatic-sulphide and laterites. About 40% of world nickel production is resulted from laterite ore in which Indonesia is listed as one of the largest nickel laterite resource countries in the world. Currently, the Indonesian nickel laterite ore has been processed with both pyrometallurgy and hydrometallurgy approaches industrially with the development target of 2.9 million tons yearly production by 2030. On the other hand, the awareness to implement net zero emission (NZE) has been highly considered, therefore, hydrometallurgy development becomes the most prominent alternative technology to process the low-grade nickel laterite ore. Furthermore, this review aims to provide the Indonesian nickel information comprehensively from resource, reserve, nickel ore distribution, classification, industrial development, supply chain, sustainability regarding the NZE and nickel prospects in the future. Moreover, depiction on the correlation of laterite nickel ore characteristic on its optimum processing technology will also be briefly presented in this review article, in order to assess the effectivity of technology implementation to process different types of nickel lateritic ores.

Exploring new methods for recycling lithium iron phosphate black mass is essential. Phosphorus, a critical raw material for the European Union, is often overlooked in battery recycling research. The standard practice involves selective leaching of lithium from lithium iron phosphate black mass, suggesting that the leaching residues can be reused directly for the synthesis of new lithium iron phosphate. Unfortunately, this aspect is disregarded by battery manufacturing companies because of the purity of the iron phosphate obtained through recycling. To address this, methodologies for the joint recovery of lithium and phosphorus are explored. Through pyrometallurgical and mechanical processes the active materials are separated from end-of-life battery cells. The obtained fraction is then leached in dilute sulfuric acid and sodium sulfide for selective leaching of lithium and phosphorus. Finally, the lithium and phosphorus are reprecipitated through pH control and heating. The overall process is simulated in the HSC Sim software for calculation of process mass and heat balance and benchmarking. All simulations are scaled with reference to a pilot plant to be constructed in Greece in cooperation with the Sunlight Group in the frame of the project “ReLiFe: Recycling of Lithium Ferrophosphate in the RIS Region.”

With the widespread application of lithium iron phosphate batteries and their limited lifespan, the disposal of spent lithium iron phosphate batteries is increasing annually, posing threats such as leakage, explosion, and combustion. These hazards endanger the natural environment, including water bodies, soil, and the atmosphere, as well as the safety of human beings and wildlife. Additionally, the substantial generation of battery waste also contributes to land resource occupation. Therefore, timely and proper recycling of these discarded batteries is essential. This serves as a crucial avenue for turning waste into wealth, not only avoiding the aforementioned risks but also enabling the reuse of valuable components like lithium. This, in turn, leads to various benefits in terms of resources, energy, environment, economy, and society. Among the components of discarded lithium iron phosphate batteries, lithium is the most valuable, as it lacks precious metals like nickel and cobalt, and the recovery value of elements like iron and phosphorus is relatively low. However, the overall lithium recovery rate from spent lithium iron phosphate batteries is less than 1%, making lithium recovery a critical focus that requires advanced techniques. Selective leaching methods, particularly those for lithium, have gained significant attention and research as green, simple, low-cost, and sustainable approaches for recycling lithium iron phosphate. This chapter comprehensively summarizes existing research progress, integrates E-pH diagrams, and analyzes the feasibility, advantages, and disadvantages of these methods.

Rare earth elements (REEs) are essential materials that play a key role in advancing modern technologies. The main sources of REEs are minerals such as monazite, bastnasite, and xenotime. Common extraction techniques include pyrometallurgy and hydrometallurgy, with the latter often preferred due to its higher efficiency, lower energy usage, and reduced air pollution. However, hydrometallurgy poses challenges, including the extensive use of strong acids, organic solvents, and the creation of considerable amounts of toxic secondary waste. This situation underscores the urgent need to develop more eco-friendly and less wasteful alternatives for extracting REEs. Supercritical fluid extraction (SCFE) emerges as a green technology for metal extraction, especially for REEs. In this study, we use a complex Canadian REE ore supplied by Avalon Advanced Materials as the primary material. We develop a unique method focusing on SCFE using supercritical carbon dioxide as the solvent, with a small amount of tributyl phosphate-nitric acid adduct serving as the chelating agent. To make this intricate ore suitable for SCFE and to achieve near-perfect REE extraction efficiency, a preliminary NaOH cracking step is applied. The optimization of various operational factors for both the NaOH cracking (including cracking temperature, NaOH to solid ratio, and caustic cracking duration) and SCFE (covering temperature, pressure, and the ratio of adduct to solid) is conducted using a comprehensive factorial design experiment method. A thorough examination of the ore samples was performed after the SCFE step to understand the mechanisms involved in the process.

Ionic adsorption clays (IAC) are formed by the natural weathering of rare earth (RE) bearing minerals and the subsequent adsorption of the rare earth elements (REEs) onto the clay surface. They can be leached from these regolith-hosted clays using only a dilute ammonium sulphate solution. Generally, the costs for extracting from such deposits are economic with very low processing costs. It is thus an attractive process if applicable. A test work organised by iTech Minerals at a commercial laboratory to extract the REEs from a clay sample achieved minimal extraction. iTech contacted METS and a metallurgical test work program was developed and executed. It consisted of ore beneficiation, REE extraction by ion exchange desorption, sulfuric acid baking followed by water leaching, hydrochloric acid leaching and their combinations. The work revealed that the material was not an ionic clay but beneficiation by simple screening resulted in almost doubling of the REE grade while also producing a kaolin by-product. Leaching with hydrochloric acid, yielded an average of 87% extraction of the REEs including more than 90% of the neodymium, while allowing also almost complete recycling of the unconsumed acid. Clearly, these would have a substantial positive impact on the CAPEX and OPEX of its application.

Furnace refractory lining is the protective layering in the furnaces that allows them to operate at high temperatures allowing for efficient metal smelting over extended periods of time. Over time, this lining deteriorates due to intense process conditions, causing problems for the furnace’s performance and efficiency. The wear of refractory linings in metallurgical furnaces can result in various failure modes, such as metal leaks due to gaps in the refractory lining, run out due to refractory thinning, run out due to metal penetration, and sidewall collapse due to thinning of load-bearing refractory. Hence, to protect the asset it is crucial to monitor the furnace’s refractory conditions. However, this requires a multivariable system setup that includes initial design parameters, baseline measurements, and follow-up risk-based inspections and monitoring. Utilizing technologies such as fiber optics, thermocouples, AU-E, and acoustic emissions in combination with frequent audits and physical measurements has proven effective in monitoring refractory wear and gap formation, detecting chemical attacks within the lining and preventing leaks and run outs, and minimizing furnace downtime and even contribution to the extension of furnace campaign life. In this paper, we discuss the cause and effect of refractory wear and the combination use of technologies to inspect and monitor furnace lining and crucible.

To better utilize the Si waste in photovoltaic (PV) module production, especially the kerf waste generated during the diamond wire sawing (DWS), hydrochloric acid (HCl) leaching as a purification method has been examined. The process parameters include HCl concentration, solid-to-liquid (S:L) ratio, and leaching period. The composition of the samples was determined via X-ray diffraction (XRD), and inductively coupled plasma optical emission spectroscopy (ICP-OES) which revealed the presence of Al and Fe impurities. Leaching with HCl shows promising results in terms of impurity removal from silicon, which in turn leads to potential application in various industries.

In the secondary steelmaking process, scrap from various sources is melted in an electric arc furnace (EAF), producing dust containing valuable metals such as zinc, iron, copper, and nickel. Despite extensive research, both the complex composition and metal speciation of the dust have impeded process development. Current recycling processes for EAF dust are primarily pyrometallurgical, relying on carbothermic reduction with solid coal in a rotary kiln to separate and recover zinc and iron in oxide form. To reduce carbon dioxide emissions in EAF dust recycling, this study proposes using hydrogen as the reducing agent. The study employed thermogravimetric analysis (TGA) to investigate the hydrogen reduction of EAF dust. Non-isothermal experiments were conducted at heating rates of 5 °C/min in hydrogen within the temperature range from room temperature to 1000 °C. Nucleation (two-dimensional) at 540–640 °C with an Ea of 39.4 kJ/mol and phase boundary control at 650–750 °C with an Ea of 108.5 kJ/mol, best describe EAF dust reduction.

To clarify the liberation mechanisms of electronic scrap (e-scrap) in the comminution process, we attempted to express the degree of liberation with a first-order kinetic equation by using impact energy obtained from discrete element method (DEM) simulations. Breakage energy measurements, comminution experiments, and DEM simulations were conducted on two types of e-scrap: connecting components and switching components. A high correlation was obtained between the results of first-order kinetic equations based on the specific impact energy from the DEM simulations and the degree of liberation observed in the comminution experiments. Furthermore, two cases of impact energy, total impact energy and impact energy above the threshold value required for liberation by breakage energy measurements, were compared. For connecting components, the latter showed higher correlation in the initial stage of comminution, while the former showed higher correlation after a certain progress of comminution. This suggests that after certain progress of comminution, structural weak points were created, and the plastics were destructively separated by smaller impact energy. On the other hand, for switching components, a high correlation was consistently obtained for impact energy above the threshold value. This might be because the metal parts are spot-jointed with a certain strength. The above results suggest that the degree of liberation of e-scrap can be expressed by a first-order kinetic equation based on the specific impact energy and that the liberation behavior can be examined by the correlation analysis of first-order kinetic equation using a threshold value.

With the depletion of high-grade nickel sulfide ores and the growing demand for green nickel, it is imperative to study the feasibility of extracting nickel from unconventional resources such as low-grade ultramafic nickel sulfide ores. The ultramafic nickel ores contain pentlandite, pyrrhotite, as well as magnesium silicates. The established smelting technique is limited to processing ultramafic nickel concentrates due to the high MgO levels. The authors proposed a two-stage solid-state thermal upgrading process by metallic iron addition to extract nickel into a ferronickel alloy. The present study investigated the effect of the nickel content of three ultramafic concentrates with %Ni = 7, 7.7, and 8.1, on the effectiveness of nickel extraction. Nickel extraction to ferronickel, nickel grade in the alloy, and the ferronickel particle size were compared.

This research investigated the feasibility of a two-stage acidic leaching process for the treatment of copper-gold concentrates. In the first stage, copper is leached in concentrated ferric chloride solutions, while in the second stage, gold is leached in the presence of thiocyanate (SCN). The study used a copper-gold concentrate containing 45.3% copper, 20.7 ppm gold, and 259 ppm silver from a mine with saline water containing up to 4 M chloride. For the first stage of leaching, reactor leaching tests were carried out to investigate the effect of solid content, temperature, and chloride concentration on the copper extraction. The leach residues from this stage were then subjected to the second stage of leaching, where the effect of thiocyanate concentration on copper, gold, and silver extractions was studied. The experimental results show that in the first stage, nearly complete copper dissolution was achieved in the presence of 3 M chloride at 85 °C within 6 h, with over 90% of sulfide sulfur oxidized to elemental sulfur. Iron was dissolved and no iron precipitation was observed during the first stage of leaching. Approximately 97% of silver was dissolved in this stage. In contrast, gold dissolution was limited due to the high potential required for gold dissolution in chloride media. In the second stage, 88.5% of gold was leached within 1 h in the presence of 0.05 M thiocyanate at 85 °C. Compared with cyanidation, this process eliminates the need for neutralization and the side reaction between elemental sulfur and cyanide, thus reducing reagent costs.

The depletion of the high-grade Ni sulfide ores has resulted in efforts aimed at processing the alternative low-grade ultramafic ores. However, these ultramafic ores contain considerable MgO, silica, and gangue rocks, challenging their processing. Smelting has been predominantly used for Ni extraction from sulfide ores as hydrometallurgical methods are associated with vast chemical usage and wastewater. However, high smelting temperatures (>1300 °C), refractory corrosion, and significant emissions remain the main smelting drawbacks. Thus, we explored the thermal treatment (<1000 °C) of the ultramafic Ni concentrates blended with Fe additive as a promising approach with mild processing conditions for upgrading these concentrates. The heat-treated product primarily comprises a magnetic FeNi alloy and a non-magnetic gangue suitable for subsequent physical separation. However, the formed FeNi particles are fine and dispersed in the gangue, lowering magnetic separation efficiency. Thus, adequate growth of the FeNi particles is imperative to guarantee their effective separation from the gangue. This work systematically investigated the effect of various heating temperatures to decipher its impact on FeNi particle growth.

Melt filtration is a well-established melt treatment procedure in steel and aluminum casting to improve the cast quality. For this purpose, various ceramic filter materials are used, with carbon-bonded alumina prevalently used in steel melt filtration. Several factors are considered when evaluating the suitability of a filter material such as the interaction between the melt and filter material, the filter’s thermal stability, and its thermal shock resistance. This study aims to investigate the properties and behavior of carbon-bonded alumina in copper melt filtration. The wetting and chemical interactions of carbon-bonded alumina with the copper melt were characterized by sessile drop tests and post-mortem SEM/EDX analysis. Additionally, the filtration behavior was evaluated with the help of sand-casting trials. It was found that copper does not wet carbon-bonded alumina and that no interaction occurs under vacuum and argon atmospheres. Investigation of the solidified metal cast with the filters shows pores in the copper surrounding the carbon-bonded filters, a product of the reaction between the melt and the carbon-containing filter surface.

Flash smelting is the major primary heat treatment process in copper smelting. The overall reaction of the process is the oxidation of sulfide copper concentrates by oxygen-enriched process gas, which is complete in a few seconds at 1400–1600 °C. Various materials lead to other reactions, including reduction and sulfidation. An increasing amount of recycled materials is used in flash smelting furnaces to achieve greater materials conservation. However, the copper contained in recycled materials can have a negative impact on the process due to the risk of liquid copper penetrating to, and damaging the furnace refractory. In order to avoid this catastrophic incident, sulfidation of copper is desired so that it enters the bath as sulfide and not metal. This study focused on the sulfidation behavior of metallic copper under flash smelting furnace conditions to understand the opportunity and its limitations. The specimens of copper concentrate mixed with metallic copper were rapidly heated and quenched in a tube furnace. Argon atmosphere was introduced to eliminate oxidation and investigate the sulfidation mechanisms. In argon, the sulfidation of metallic copper proceeded faster than the complete sulfur evaporation from copper concentrate. Furthermore, oxygen was injected to simulate the flash smelting furnace conditions in which the exothermic oxidation reactions of copper concentrate occur, and sulfur is promptly oxidized to sulfur dioxide. Different sizes of metallic copper particles were used to study the effect of the surface area.

Previous developments in the simulation of metallurgical operations led to the representation of alternating modes of operation. These operating modes are initially described as mass balances within a system of nodes, representing the components of the metallurgical plant, to a higher or lower degree of resolution, depending on the data available, and the objective of the simulation. As an engineering project progresses, the modes are represented in increasing levels of detail, focusing on the most critical aspects, i.e., the critical opportunities driving a project forward, and also the critical risks and threats that are obstructing progress. Whereas a high-level representation considers dynamic mass balances, and the fluctuating material contents of reactors (grinding mills, flotation cells, thickeners, etc., in the case of mineral concentrators, or furnaces and ladles in the case of smelters), a detailed representation may eventually benefit from immersive experiences, within a computer-powered virtual reality (VR) representation of the plant. The data generated by operators and engineers in VR can inform continuous improvement and reengineering projects for existing plants, as well as the later stages of a greenfield project (detailed engineering and ramp-up). Furthermore, VR representation of metallurgical plants is of pedagogical value for engineering students, likely impacting how future metallurgical engineers will execute their projects. The current paper presents the progress and feedback from a VR development of a fictitious concentrator and describes how these efforts could be merged with the simulation testing of machine-learning-enabled control systems and other emerging challenges in mineral processing and extractive metallurgy.

Over the past six decades, Hatch has been engaged in design, development, and construction of many engineering projects in the mining, metals, and chemicals industries. Throughout those projects, Hatch engineers have helped their clients to transform exploratory stage of projects to their commercialization through the most economical processes. To support such transformations, Hatch has planned, designed, and executed numerous successful testwork programs at laboratory scale, pilot plant, and demonstration plant scales. The development of a sound metallurgical testwork program provides a semi-empirical method (based on both theoretical research and practical experience) to supply reliable design data to select and size process equipment and create a profitable and feasible process flowsheet. In this paper, an introduction to metallurgical testwork programs, the main reason to perform such tests, and related methods are presented. It is followed by a discussion of some practical cases from Hatch’s years of experience, from which a framework for testwork planning at the various stages of engineering was developed. Finally, in order to provide a thorough understanding of metallurgical testwork programs, possible reasons for the success or failures of testwork programs are discussed.

There are many factors that should be considered when scaling up chemical processes. However, too often a rigorous assessment of key deliverables from pilots and demo plants is not done, in favour of “base 10” throughput values (1 tonne per day, 10 L/min, 50 kg total). In addition, the review of the reasons why the pilot is being done (beyond showing investors that the scale-up is possible) will give a strong basis for the work and also help to identify design of experiment deficiencies that could reduce the value of the pilot/demo. Some of the factors that will be discussed include sampling and homogeneity, equipment issues, controls, recycle streams, and subsequent materials qualification needs. With a well-planned scale-up, the important factors can be addressed early and de-risking of the project is much more focussed. This chapter will discuss how quantitative analysis of these factors can be used to justify the scale, duration, degree of integration, flow rates, and other features of a pilot/demo plant to ensure that the scale-up maximizes its value

The increasing demand for explosive-free rock breakage systems in mining engineering and space industry applications has prompted a focused investigation into novel techniques. Ensuring efficient hard rock breaking and preventing rock burst disasters are paramount considerations, particularly in deep construction areas with high in-situ stresses. This study delves into the laboratory-scale exploration of the impact of high voltage pulse (HVP) and cryogenic fluid (CF) fracturing on permeability and porosity changes in synthetic hard rocks. The experimentation involved varying voltage levels and immersion duration in liquid nitrogen. Using a gas porosimeter-permeameter instrument, the study revealed a remarkable up to 1,710,669% increase in permeability, showcasing the efficacy of these techniques in enhancing rock permeability. Furthermore, notable cracks were observed on the samples, serving as visual evidence of the transformative effects. The cryogenic fluid treatment demonstrated the gradual formation of a connected network of microcracks. The study emphasizes that rock type and initial porosity, significantly impact the intensity of mechanical damage induced by cryogenic fluid treatment. This research provides crucial insights into the realm of explosive-free rock breakage, laying the groundwork for further exploration of HVP and CF fracturing in real-world applications.

In 2023, Aurubis announced a comprehensive makeover of its precious metals refinery. In addition to upgrading precious metals’ security and occupational safety, Aurubis is raising the bar with the innovative process technology realized in this project. Today’s process is based on refining a silver Doré in a Möbius type silver electrolysis and subsequently treating the residual anode slime in a combined nitric/chloride gold refining and platinum group metals (PGM) solution production. In the future, Aurubis will still rely on silver electrorefining but with significantly increased contents of gold and PGMs and much higher current densities remarkably speeding up the refining. The resulting anode slimes will be treated in a direct chloride leach making it faster and decreasing its environmental impact. In this chapter, we will discuss the role of R&D at the different stages of the project. Based on a feed assumption different flowsheet options were evaluated in an ideation phase. In the following, we conducted lab tests to develop the selected flowsheets. Finally, the flowsheet was piloted and some parts were even tested for full production scale. All these results were used to compile process design criteria which are being used for the ongoing engineering of the new plant. In addition to the general aspects of the transformation itself, we will focus on the different key development steps and challenges during the individual stages of the project. The newly developed metallurgical process leads to higher efficiency, which will considerably reduce throughput times for materials containing precious metals.

The ongoing trend of reduced CO2 emission targets by both governments and corporate entities has brought with it a significant push for new processing routes of non-conventional feedstocks, use of new technologies, and the application of existing technologies in new ways. Two prominent examples are: (1) Recycling of waste materials such as EOL/scrap batteries or production of refined products from multiple intermediate products (MHP, matte, black mass, etc.) where market availability carries significant uncertainty; (2) Electrification of conventionally carbon-intensive processes, such as green steel technologies, which drives the application of conventional electric smelting technology to a new process. As for all new technologies and processes, there is a commercialization risk that can be mitigated through appropriate process development, testwork, piloting, and demonstration. However, the environmental and political urgency means that these risks must either be mitigated on an accelerated timescale or, to a degree, accepted. This results in unprecedented challenges in engineering project development. This paper examines the growing challenge of advancing technology readiness and engineering projects in parallel and how a Technology Readiness Assessment (TRA) framework can be used to develop a suite of mitigations, including testwork and equipment design, and to set project expectations that enable the best chance of success.

Anode slime is the by-product of copper electrorefining and contains precious metals, crucial for several industries, such as automobiles, petroleum, chemicals, electronics, glass manufacturing, and medical implants. Considering our materials-intensive future, alongside the imperative to prioritize green technologies, and transition from a linear economy to a circular economy, a focus on optimization of multi-metal recovery such as that of precious metals in copper flowsheets is increasingly necessary. Copper anode slime undergoes different treatments, including pyrometallurgy, hydrometallurgy, and hybrid processes, to recover these elements. The slime’s composition and phases, type of treatment, and choice of technology affect the metal recovery rate. This work aims to provide a state-of-the-art overview of slime treatments and technologies envisioning optimized resource recovery and fostering sustainable practices in metal production.

This paper describes the current best practices and critical steps of developing metallurgical test plans and the final important step to process the design of a circuit. No two deposits are the same, and developing test plans that address the geology and ore domains is a complex task. Sample selection and ore characterisation to understand the metallurgical response of an ore are only the start. Invariably, test plans need to be updated based on the results received. The testwork needs to be considered as a project with the scope of work, schedule, cost, quality, safety and environment the new norms required. It needs to be managed using the best project management knowledge available. The data interpretation of the results is the most difficult part and requires personnel skilled in the art as well as benchmarking and discussing with vendors and reference to existing projects. Project failure analysis often highlights where gaps in knowledge existed and the interpretation of the metallurgical results was deficient. In some cases, this may require piloting of the process to improve process confidence, reduce risks and provide engineering data. Often this is all summarised in a metallurgical summary report. Process design is the final step and has its own challenges with regard to not being too conservative but ensuring the design is functional and operable. A number of examples are provided highlighting the lessons learned.

During leaching tests of different Aurubis anode slimes, decreased copper, and nickel leaching yields were observed for one particular slime. This anode slime had a higher copper, nickel and antimony content than the others. To identify the reason for this behavior mineralogical investigations of the slime before and after leaching were performed. These showed only low amounts of copper and nickel oxides but considerable amounts of a CuNiSbO species. There have been several studies on the species called kupferglimmer, Cu3Ni2–xSbO6–x. It is known to have a refractory nature, which poses a challenge for further anode slime processing. Higher amounts of residual copper and nickel in the leached slimes lead to capacity problems and difficulties during silver and precious metal processing. Thus, in this study the conditions in anodes leading to specific anode slimes of certain compositions and mineralogies were investigated together with the resulting leaching behavior. When the higher antimony levels were accompanied by higher lead levels in the anodes, the copper content of the slime decreased, and leaching yields for copper and nickel improved.

In 1998, Terry McNulty presented an SME paper that surveyed 41 processing plant case histories and identified the dominant causes of success and failure. That survey resulted in creation of four curves, graphically portraying the approximate rates of achievement of design capacity over time for projects that ranged from very successful to marginal to unsuccessful. Identifiable characteristics of those projects were then tabulated, establishing rough guidelines that could be used in project planning or for prioritization of projects competing for capital. Updates were given at SME 2004 in Denver and at COM 2014 in Vancouver. These so-called “McNulty Curves” have been widely adopted by operating companies and project financing firms for use as a checklist for risk assessment. We are offering an update based on responses to questionnaires sent in early-2024 to mining and mineral processing companies around the globe and to consulting metallurgists and EPCM project managers. Adding new case histories and incorporating the advice and suggestions of respondents has shifted the original curves and hopefully improved their usefulness. Also, the specific problems encountered by some projects are discussed in detail, along with recommendations from responders about ensuring success.

A sample of Cu/Co flotation concentrate from Oz Minerals’ Carrapateena mine in Western Australia was subjected to sulfation roasting under conditions predicted to favor conversion of copper and cobalt sulfides to sulfates. Most of the past attempts by plant operators and many researchers to apply sulfation roasting to primary sulfide minerals, including bornite and chalcopyrite, have generally failed. The obstacle to success has been formation of the acid-insoluble copper ferrite. The only sulfation roasting and roaster calcine leaching project that has ever achieved commercial scale for chalcopyrite concentrates was the Lakeshore operation in southern Arizona in the 1970s. Since Lakeshore was eventually a financial failure, this paper summarizes the operation’s technical features and history and demonstrates that sulfation itself was successful. Following a literature search, two thermodynamic studies were conducted, and an operating window for sulfation by fluidized bed roasting was found to be 650–680 °C with an air-to-solid mass ratio of 18:1. Leaching of the calcine with dilute sulfuric acid extracted 97% of the copper and 83% of the cobalt. The residue was washed, neutralized, and leached with aqueous sodium cyanide, resulting in extractions of gold and silver, respectively, of 99 and 78%.

There has been significant schedule pressure recently on projects in the extractive metallurgy industry. This pressure has come primarily from the transition of the energy economy to create the capacity for “greener” processes and products. Examples of this trend include the battery materials and automotive space, which seeks to rapidly bring online new capacity for electric vehicles, and the displacement of carbon-based fuels used in traditional metallurgical processes. Achieving these noble goals requires innovation and novel technologies to be part of these projects. Moreover, there is immense pressure on the extractive metallurgy industry to implement projects faster and with less definition, which leads to increased project risk and often the instinct to streamline effort development, engineering, and execution. A clear understanding of key factors in successful fast-track projects is needed to avoid excessive streamlining, resulting in disappointing project outcomes and even worse, a safety incident that causes irreparable harm. The authors have identified key success factors based on projects that achieved positive outcomes in the current aggressive market.

In recent years, the demand for lithium-ion-batteries (LIBs) for electric vehicles and fixed power storage has experienced explosive growth, resulting in a substantial increase in worldwide lithium consumption. To meet the growing demand, lithium-bearing minerals and lithium recycling from end-of-life (EOL) LIBs have attracted much attention. However, the lithium extraction and recycling processes bring a challenge: the production of a significant amount of sodium sulfate. Sodium sulfate, a white crystalline type of salt, is a seemingly innocuous byproduct. It is used in various industries, from manufacturing detergents and textiles to glass and paper. However, when it is produced in bulk as a by-product of battery-grade lithium hydroxide, lithium carbonate, and pCAM, its limited application may be overwhelmed by the disposal cost.In this article, the hydrometallurgical processes for extraction of lithium from ores, brine, and battery recycling with sodium sulfate as a by-product are discussed. Alternative and environment-friendly processes to valorize sodium sulfate are reviewed.

Metals are key to achieving the global energy transition to a low-carbon world. Carbon emissions in primary metal production are also under scrutiny. In particular, efforts are underway worldwide to reduce carbon emissions from the global iron and steel-making industry, which at present produces about 9% of global carbon dioxide emissions. The four metals next to iron and steel in combined tonnage (Al, Cu, Zn, and Ni) represent a significant 3.5% of global carbon dioxide emissions based on the author’s estimate, and incremental improvements to existing technologies and development of new processes have started. This paper discusses new approaches for both the iron and steel and non-ferrous industries, including the potential use of hydrogen as a chemical reagent. Pilot plant testing of new technologies will be key to developing robust future plants. A brief look at historical timelines in selected successful piloting and commercialization experienced in the iron/steel and nickel industries is included in this extended abstract.

The study investigated opportunities for improved geometallurgical practices at the Jerritt Canyon Smith gold deposit. The sequential Gaussian simulation (SGS) method was used to characterize the geological variability within the deposit domains. Sensor-based bulk ore sorting was introduced as the enabling technology that can classify mined materials based on their geometallurgical properties in real time. The impact of the simulation-based modelling and bulk ore sorting was evaluated in terms of metallurgical results and mine economics. Compared to the ordinary Kriging interpolation approach, the SGS simulation method more accurately captured the grade variability allowing improved understanding of the orebody geometallurgy. For different domains of the Smith deposit, the metallurgy and economic benefits of bulk ore sorting vary, representing different geometallurgical classification potentials across the deposit. High-resolution sortability mapping was established to guide the geometallurgical classification of the mined material. In conclusion, the study demonstrated the integration of simulation-based modelling and sensor-based bulk ore sorting for improved geometallurgical practices.

Drying is a critical step in the processing of minerals, with substantial energy demand, resource cost, and greenhouse gas emissions. In this work, the performance of microwave systems for drying minerals was experimentally investigated. Different materials with distinct chemical compositions and moisture contents ranging from 5% to 25% were chosen and their thermophysical and electromagnetic properties, including dielectric loss, thermal conductivity, and heat capacity were characterized. Materials were incrementally heated in a 2.45 GHz microwave oven with subsequent measurements of mass loss and surface temperature until certain mass losses were attained. The dry materials showed minimal interaction with the applied electromagnetic field, but with discernible energy exchange in the presence of moisture which points to the potential of microwave systems in the drying of materials. Results showed a consistent drying rate up to a critical moisture content, followed by a falling rate regime. Conventional drying methods face challenges in reaching and surpassing the critical moisture content, often requiring prolonged residence times. These findings show that microwave heating is an excellent alternative for drying applications in mining with low net energy demands and greenhouse gas emissions.

Fine bubble generators are being used in various applications because of the superior performance that is generally achieved with smaller bubble sizes. In mineral processing, spargers are used in flotation circuits to separate valuable minerals and the gangues; and used to inject oxygen that is required for the cyanide leaching reaction. Eriez offers several sparging technologies for different applications. This paper covers two applications where Eriez’ SlamJet™ spargers were incorporated into existing circuits to provide added value.

Many technical papers focus on the “What” of new metallurgical furnace technology, i.e. What technologies to use and why. This paper instead concentrates on the “How”: How to successfully execute furnace rebuild/upgrade projects to achieve the expected benefits, and without overrunning the capital budget and/or time schedule. There is some commonality between the success factors for executing furnace rebuild projects and those for projects generally, i.e. safety is paramount. However, these rebuild projects have additional constraints, such as minimum shutdown schedule to avoid excessive lost production, key equipment only available from overseas vendors with long lead times, and the need for specialist skills such as furnace demolition contractors, refractory installers, and heat-up specialists. A furnace is rebuilt/upgraded typically only once every 5 or 10 years, and in that time owners tend to lose some of the institutional lessons learned from their previous furnace rebuilds. Based on our delivering multiple furnace rebuilds for clients each year, we have codified in this paper key success factors. Concepts discussed include first defining the “Why” to derive the scope; project phasing; front end engineering design (FEED); quantitative risk assessment; construction sequence (4D) simulation; pros & cons of various contracting strategies; modularization and design for construction; use of third-party specialist contractors and experts, etc. Examples discussed include the rebuild/upgrade of: a six-electrode-in-line ferronickel furnace in Brazil. a copper flash smelting furnace (FSF) in Japan. a copper flash converting furnace (FCF) in the United States. a nickel slag cleaning furnace (SCF) in Finland.

The handling of process intermediates at Aurubis AG is a topic that grows as our smelter network expands. In this work, higher Sn recoveries were achieved by identifying a new processing route for a CuPb intermediate. Handling of impurities such as Sb and As became important learnings over the course of process development. Mitigating impurity effects requires a sequence of process development steps through modelling, testing, and data-driven decision-making. The concept leverages multiple Aurubis sites’ existing capabilities to separate the Cu from the Pb and Sn. The metallurgical process concept was first devised as a process flowsheet model and then reviewed by Aurubis metallurgists. Following this, a sequence of three test phases took place directly in operation, each larger in scope than the previous and each with specific questions to be answered. As the trial progressed, it moved from a technical focus to a stakeholder management focus. Data-driven consistency and openness were required between all stakeholders so each could understand the impact of the intermediate on their process, give feedback on concerns, as well as stop mechanisms if production was affected to a pre-aligned value. Aligning local site KPIs with overall group KPIs was key, along with steady communication to build acceptance of the new process and ultimately allowing long-term implementation. Ultimately, the project was able to treat the CuPb intermediate at a steady state within the span of 1 year.

The electric arc furnace accounts for approximately one-third of global steel production. Even in scrap-based electric arc furnace steelmaking, achieving the target phosphorous content in the final steel product poses a challenge. Enhancing dephosphorization efficiency requires consideration of various initial conditions and operational parameters, rendering process improvement both scientifically and technically demanding. In this study, an artificial neural network model was employed to predict the end-point phosphorus content of steel. A dataset comprising over 1760 entries with 12 input parameters was collected from the plant. Rigorous data processing techniques were applied to enhance both dataset quality and model performance. The findings demonstrate that the model can accurately predict the final phosphorus content of the steel, at least within the tested operational conditions.

The circular economy mandates the processing of waste from metallurgical and mining operations, an endeavor fraught with social, technical, and economic challenges. Frequently, there are large amounts of these materials, which have limited value and contain nuisance elements that must be removed and sequestered to produce a viable product. Time-consuming research, development, and engineering are required to create and prove new processes. The Inco Iron Ore Recovery Plant operated from the mid-1950s to 1983. It was a “circular economy” operation, which recovered all values contained in the pyrrhotite feed to produce marketable nickel oxide, iron ore, sulfuric acid, and steam. The development process identified suitable equipment and process conditions for (a) high-temperature roasting/selective reduction of pyrrhotite, (b) selective ammonia leaching, reagent and nickel recovery, and (c) agglomeration and induration of fine iron oxide. Technology development lasted 8 years, 1947–1955. The development process employed by Inco, a technology leader of the time, involved the same procedures we use today—paper and laboratory studies, extensive piloting, and semi-commercial testing with external partners—but in a more favorable social, economic, and business environment. Based on a contemporary account, this chapter describes the development process and technical hurdles overcome to create the iron ore recovery plant and compares what would be encountered today when entrepreneurs, designers, and engineers face significantly greater business, environmental, and social hurdles. International Energy Agency targets mandate increasing reprocessing and recycling, i.e., reach a circular economy. We must take actions to accelerate the development process while maintaining guardrails against wasteful and harmful projects.

The Gram-negative acidophile Acidithiobacillus ferrooxidans is capable of exocellular iron reduction through an electron transfer chain that spans both membranes and the periplasm. Four redox proteins are required to transfer electrons to Fe(III): (i) the inner membrane-anchored c-type cytochrome CycA, (ii) the periplasmic c-type cytochrome Cyc1, (iii) the periplasmic blue copper protein rusticyanin (Rus), and (iv) the outer membrane c-type cytochrome Cyc2. To investigate the Fe(III) reduction functionality of this pathway in neutrophilic hosts, it was reconstructed in three different Escherichia coli strains and Vibrio natriegens Vmax X2. The periplasmic proteins Rus and Cyc1 were only produced as membrane-associated proteins in E. coli and no holo-CycA was detected in E. coli cell extracts. V. natriegens produced all four holo-proteins simultaneously while the periplasmic proteins Rus and Cyc1 remained soluble. UV/Vis spectra of soluble cell extracts of V. natriegens showed typical absorbance maxima for heme c. The c-type cytochromes produced by V. natriegens could also be reduced and oxidized. Therefore, V. natriegens seems to be a very promising host for the production of soluble periplasmic as well as membrane-anchored proteins from an extreme acidophile.

Cyanidation, a conventional process to extract gold from gold ores, has been used for over 130 years in industrial mining because of the high efficiency and rate of formation of Au(CN)2− and the high recovery efficiency by adsorption of Au(CN)2− on activated carbon. However, carbonaceous refractory gold ores are not targeted for recovering gold because Au(CN)2− is easily adsorbed on carbonaceous matter in the ores, resulting in high recovery loss. In this study, carbonaceous refractory gold ores were subjected to biooxidation at 45 °C using a mixed culture containing iron-oxidizing and sulfur-oxidizing bacteria, following which gold was extracted using thiourea under strongly acidic conditions. The gold extraction rate reached ~100% in 12 h without re-adsorption. Finally, the quantitative recovery of the Au(CS(NH2)2)2+ complex was confirmed by adsorption on strongly cationic exchange resin. The recovery process involved these aspects: (1) biooxidation with the mixed culture containing iron- and sulfur-oxidizing bacteria facilitated sulfide dissolution without the accumulation of elemental sulfur, (2) biooxidation reduced the amount of Fe-containing metal sulfides, which minimized the decomposition of thiourea, and (3) the Au(CS(NH2)2)2+ complex had a low affinity toward carbonaceous matter, different from Au(CN)2−. Since this process does not require roasting to remove carbonaceous materials in pretreatment and does not use cyanide in gold extraction, it is environmentally friendly and must be considered for practical applications in carbonaceous gold ore-producing mines.

Lithium iron phosphate (LFP) batteries are an important source of critical raw materials due to their high content of lithium, graphite, and phosphorus. The overall aim of this study is to develop a recycling process for LFP-batteries combining hydrometallurgical and biohydrometallurgical approaches for efficient recycling of lithium. As part of the biological approach, various autotrophic bioleaching strategies were tested to selectively leach lithium and to enhance the chemical leaching step of the LFP black mass in the process. Direct and indirect bioleaching approaches using biologically produced lixiviants were examined. First experiments showed leaching yields for lithium of nearly 80% with the direct leaching approach (5% w/v solid load) and maximum about 80% for the indirect bioleaching approach (7% w/v solid load). The results of this study demonstrate the possibilities of bioleaching for the recycling of lithium iron phosphate batteries.

GaAs wafers are essential for the production of GaAs semiconductor chips, which have a wide range of applications in manufacturing electronic devices, including power electronics, photovoltaic cells, sensors, and detectors. The demand for GaAs wafers is steadily increasing due to technological advances and growing environmental awareness, posing new challenges for the industry. During the production of GaAs wafers alone, 15% of the gallium originally used is lost during the process as liquid and solid production waste. These wastes can be considered as secondary raw materials, which should be recycled. In this study, the possibility of bioleaching the gallium from a metal hydroxide sludge, a waste product from the GaAs-wafer production, was investigated. Therefore, oxidative and reductive bioleaching strategies with 5% (w/v) metal hydroxide sludge were tested. The results showed that during oxidative bioleaching of the metal hydroxide sludge nearly 90% Ga was leached after 6 days and for the reductive bioleaching 87% Ga was leached after 8 days. However, reductive bioleaching proved to be a more attractive approach, as the treatment of the leaching solution would be more sustainable. This study demonstrates the potential of bioleaching for the recycling of gallium from waste products resulting from GaAs wafer production.

Australia is one of the main reserves of rare earth elements phosphate (P-REE) minerals. Phosphate-solubilising bacteria (PSB) are capable of dissolving the phosphate content of such minerals. It has been demonstrated that P-REE leaching efficiency is greater when microorganisms are in direct contact with the ore surface. This study investigated biofilm formation by the PSB Klebsiella aerogenes on the surface of monazite. Initial attachment occurred during the early hours of exposure and was affected by extracellular DNA (eDNA) production, particle size, physico-chemical properties of the surface, total available area for attachment, and inoculation size. K. aerogenes produced eDNA, which provides high attachment-affinity towards the surface of P-REE, hence, playing an important role during initial attachment. Attachment occurred preferentially on larger-sized particles. Analysis of the dynamics of planktonic and sessile equilibrium during initial attachment revealed greater biofilm formation in the presence of monazite compared to a glass surface, in which lowering the initial cell concentration shifted the equilibrium towards a greater sessile population promoting biofilm formation, as did increasing the total available area. Given enough time PSBs colonise the surface of these minerals and form mature biofilms, which cover almost the whole surface. Microscopy analysis of biofilm cross-sections showed a thin-layer structure. Biofilm selectively formed on and around physical imperfections but showed no selectivity towards particular mineralogy.

Algae-based technologies offer various solutions to mitigate the environmental impacts of mining during operations and after closure. Algae sequester CO2 into biomass, allowing possible offsetting of carbon emissions. Algae can also facilitate the removal of various contaminants from mine water, dust suppression, stabilisation of mine waste, and mine-site rehabilitation. The cultivation of algae at mine sites may also provide opportunities for the manufacture of valuable products such as pigments, bioplastics, biofuels, and animal feed. This presents the potential to establish a bio-based economy, creating job opportunities for local communities. The feasibility of cultivating and utilising algae requires a case-by-case evaluation of technical performance, local conditions, regulatory constraints, economic feasibility, and environmental impacts. This study aims to explore the potential of various algae-based technologies designed for cultivating, harvesting, and utilising algae at mine sites for beneficial purposes.

Bioleaching is a promising and feasible option for metal extraction from sulfidic mine wastes. The main objective of this study was to investigate how the gas–liquid mass transfer phenomena affect the bioleaching of sulfidic mining wastes, with the ultimate goal of optimizing the gas supply. Experiments were performed in four continuous stirred-tank reactors (CSTRs) arranged in series with a total working volume of 114-L. Three different gas compositions were tested: (I) air, (II) air enriched with 0.5% v/v CO2, and (III) a mixture of N2 (69.5% v/v), O2 (30% v/v), and CO2 (0.5% v/v) in the first two reactors of the series. Results showed that during Condition I, the CO2 transfer rate was not sufficient, particularly in the primary reactor resulting in a low sulfide dissolution yield. Enriching air with 0.5% v/v of CO2 during Condition II increased both sulfide dissolution in the primary reactor and oxygen uptake rate (OUR) in the entire system, which caused oxygen transfer limitations. Sulfide dissolution was further enhanced during Condition III due to increased partial pressure of O2 in the first and second reactors, achieving a total cumulative sulfide dissolution yield of 81% and the dissolution of 86% of Co and 30% of Sb contained in the MW. This study emphasizes the importance of sufficient gas supply in the bioleaching process and demonstrates that gas–liquid mass transfer considerations are crucial for upscaling and cost optimization.

Biomining, an environmentally sustainable method for extracting metals from both primary and secondary resources, has garnered significant attention in recent years. The success of biomining processes relies on the capabilities of microorganisms to produce biometabolites essential for converting solid metals into soluble forms. Among these biometabolites, siderophores, characterized as selective metal-chelating molecules, emerge as promising contributors to the field of biohydrometallurgy. This review explores the role of siderophores in biomining processes, focusing on their types, mechanisms, required conditions for production by microorganisms, and their potential to optimize metal recovery. Furthermore, previous studies utilizing siderophores for metals recovery from primary and secondary resources are reviewed, and various parameters and conditions affecting bioleaching by siderophores, such as pH, time, and siderophore concentration, are discussed. In conclusion, this review highlights the promising future of siderophore-driven biomining technologies. By understanding and using the capabilities of these molecules, researchers can pave the way for more sustainable and economically viable biomining technologies.

Effective pyrite depression is required to improve the grade of copper concentrate from a flotation process. Raw seawater can be used directly in a flotation plant to replace desalinated freshwater. However, seawater causes some problems and prevents efficient flotation. We aimed to effectively depress pyrite in raw seawater using marine iron-oxidizing bacteria (bio-flotation). Basic experimental conditions using four strains of bacteria were assessed in this study. Suitable cultivating conditions using FeS2 and FeCl2 as Fe sources were determined. Bacterial growth increased when FeS2 was used because Fe2+ was supplied more continually by pyrite than FeCl2 in seawater. The bacteria proliferated effectively at 25 °C, even though the temperature of the seafloor the bacteria originally inhabited was different. A flotation experiment was performed using a Hallimond tube after allowing the culture solution to react with 0.5 g pyrite (106–150 μm) for 30 min. The pyrite recovery was 10–20% lower after the pyrite had reacted with seawater containing Fe-oxidizing bacteria, but the pyrite recovery increased to 80–90% when the subculture (the original source of the culture used in the flotation experiment) period was longer using all bacterial strains. The bacterial cell concentrations in the experiments were 1 × 106–2 × 107 cells/mL. However, the pyrite recovery and bacterial cell concentration did not positively correlate. This indicated that the bacterial activity related to the subculture was an important factor promoting the bacterial reaction, i.e., by increasing hydrophilicity of the pyrite surface.

To enhance Au recovery from double refractory gold ores (DRGOs), a crucial step involves the oxidation of sulfides to release Au grains and degrading carbonaceous matter to minimize Au(CN)2− adsorption during cyanidation. Enzymatic degradation of carbonaceous matter in DRGOs has become attractive due to its environmentally friendly attributes. Laccases, the multicopper enzymes, have been extensively studied, primarily for their ability to degrade lignin, a precursor of carbonaceous matter. Various substrates oxidized by laccase can be expanded by mediators, lower-molecular-weight compounds easily oxidized by laccase, producing highly reactive cationic radicals that oxidize more complex substrates by shifting the chemical equilibrium. Various mediators have been identified, and laccases from different mushrooms exhibit distinct interactions with these mediators. Therefore, this study investigated the impact of different mediators in laccase-mediator systems on the degradation of carbonaceous matter in DRGOs to enhance Au extraction. The laccase-mediator system proposed represents a novel approach that deserves further attention, especially for understanding carbon science in hydrometallurgy.

The project “Recycling of mineral fractions from tailings” aims to separate pollutants and valuable materials tailings from tailings. The use of remaining mineral fractions for building materials as a secondary raw material is made possible. Bioleaching is used to extract metal, especially lead, mineral fraction, which have been recovered by flotation from tailings. For this purpose, the fractions were incubated with sulfur-oxidizing bacteria, microorganisms that form low-molecular organic acids and with low-molecular organic acids. After acidophilic bioleaching, manganese (approx. 2 g/L), iron (approx. 8.5 g/L), and zinc (approx. 1 g/L) were detected in the leaching solution. In a second campaign, microorganisms that produce low molecular weight organic acids were used, and the growth of these microorganisms was inhibited. In a third, series of experiments culture supernatants with desired low molecular weight organic acid were used for leaching. With this process, 50% to 60% of the lead contained in the mineral fraction were leached.

Conventional mining and extraction methods for rare earth elements (REEs) are energy-intensive and environmentally harmful. Bioleaching processes offer a promising and eco-friendly approach to enhance the sustainability of REE extraction. This study evaluates the potential of bioleaching REEs from unprocessed carbonatitic and alkaline bulk rocks. Bioleaching experiments were conducted on a Carbonatite sample from the Fen-Complex (Norway) and two nepheline syenites (a Grennaite and a pegmatitic Grennaite from Norra Kärr, Sweden), utilizing the heterotrophic organisms Yarrowia lipolytica DSM3286 and Tea consortia Kombucha. The results demonstrate varying recovery rates based on mineralogy and leaching methods, with preferential leaching of light or heavy REEs depending on the selected organisms. Notably, the highest leaching efficiency of 54% REE recovery was achieved with Y. lipolytica DSM3286 supernatant leaching on pegmatitic Grennaite during a 19-day experiment. Carbonatite and Grennaite samples exhibited lower maximum leaching rates of 5% and 8%, respectively. The findings demonstrate the proof-of-concept feasibility of bioleaching REEs from unprocessed bulk rock materials and highlight its strong potential, especially in providing a sustainable solution for utilizing low-grade ores and mine waste.

Bioleaching as a method for extracting metals from low-grade ores is gaining attention due to its potential as an alternative to energy-intensive and less-efficient metallurgical processes. Furthermore, increasing the chloride concentration in bioleaching environments may enhance the efficiency, thus raising the interest also in halotolerant acidophilic iron oxidizers like Sulfobacillus thermosulfidooxidans. This study aimed to compare the chloride tolerance of various Sulfobacillus species. The results showed that Sb. thermosulfidooxidans exhibited the highest tolerance compared to other tested strains. Based on the knowledge, that yeast extract (YE) may have a positive impact on the chloride tolerance of microorganisms, the importance of single YE components on bacterial respiratory activity was also investigated. The experiments showed that in Sb. thermosulfidooxidans casamino acids with potassium and glucose can be applied to replace the yeast extract. Moreover, ultrafiltration of casamino acids indicated the importance of small peptides or amino acids (<1 kDa). This study contributes to the understanding of the requirements for creating a defined medium for an efficient bioleaching process in the presence of chloride ions involving Sb. thermosulfidooxidans.

The bioleaching of the Ag-bearing tetrahedrite mineral originating from the Strieborná vein of the Rožňava mine in eastern Slovakia was investigated. Tetrahedrite from this site is of interest not only because of high Cu (40–46 wt%) and Ag (up to 1%) grades but also because of the potential for Sb recovery. The polymetallic Ag-Cu-Sb-siderite ore sample was dry crushed and milled to a grain size <100 μm. The ground ore was further upgraded by froth flotation and acid leaching, producing a final siderite-free tetrahedrite concentrate. The bioleaching of the concentrate was carried out in an acidic sulfate medium (pH ~ 2) by iron-oxidizing bacteria Acidithiobacillus (At.) ferrooxidans, At. ferrivorans SS3, and Leptospirillum ferriphilum under aerobic conditions at 25 °C. The bioleaching experiments were performed in a 250 mL shaking flask at 190 rpm, with a pulp density of 2%. The period of bioleaching was intentionally extended to 210 days in order to monitor the concentration changes of individual metals and metalloids in the leachate. While the recovery of Cu and Zn increased proportionally with time, the Sb concentration approached 665 mg L−1 (equivalent to 12.7% yield), on approximately the 30th day of bioleaching and subsequently decreased. The concentration of Cu and Zn in the leaching liquor approached 4800 mg L−1 and 115 mg L−1, respectively, which is equivalent to 75% metal yield. The bacterial activity was monitored by online gas analysis using a multichannel respirometric system to monitor O2 consumption during bioleaching.

Sulfur-oxidizing Acidithiobacillus thiooxidans has been shown to mediate ferric iron reduction at low pH under aerobic conditions. This was attributed to a nonenzymatic process involving sulfur intermediates formed during the sulfur oxidation and has already been successfully used for reductive bioleaching. However, the aerobic ferric iron reduction cannot be attributed to sulfur oxidation alone as hydrogen-grown At. thiooxidans also reduced ferric iron under aerobic conditions. Therefore, we compared the proteome profiles of ferric iron-reducing and nonreducing At. thiooxidans cells to reveal potential enzymes involved in the ferric iron reduction mechanism. The most elevated proteins in ferric iron-reducing cells were those involved in sulfur metabolism (sulfide quinone reductase, sulfur-reducing protein DsrE, oxidative cytochrome c-type SoxX), supporting the chemical mechanism of ferric iron reduction by inorganic sulfur compounds. In addition, redox proteins, including flavoproteins, FeS-containing proteins, and quinoproteins, which may play the role of iron reductases in the enzymatic mechanism of ferric iron reduction, were significantly increased. This study provides new insights into the mechanism of aerobic ferric iron reduction in sulfur-oxidizing At. thiooxidans, which involves an interplay of nonenzymatic and enzymatic processes. On the one hand, enzymatic processes promote the formation of sulfur intermediates, thereby reducing ferric iron nonenzymatically, which is further enhanced by enzymatic ferric iron reduction by redox proteins.

Mining operations in northern Ontario, Canada, have generated substantial quantities (50–100 million tons by dry weight) of pyrrhotite tailings over recent decades. Untreated tailings containing up to 1 wt% of Ni are considered waste and can cause acid mine drainage (AMD). To mitigate the potential AMD hazards due to atmospheric oxidation, these tailings are stored underwater. Metso’s BIOX® process is well-known for its commercial success in treating gold-bearing sulfide minerals, primarily pyrite, due to its simplicity and robustness. This study aims to test the BIOX® bioleaching process for nickel extraction from pyrrhotite. Semi-batch BIOX® bioleaching experiments were conducted to investigate the efficiency of nickel extraction, the elemental sulfur yield, as well as the optimal combination of pH levels in each stage. Based on experimental data, the process was modeled with the HSC software and compared with a two-step process we have previously studied.

The extraction of metal from parent ore is influenced by many factors including microbial ones. It is now clear that microorganisms provide the space for biological and chemical reactions to occur and produce the necessary ferric ions and protons for leaching. Microbial dynamics within bio-hydrometallurgical and bio-oxidation processes are critical to their performances, and a fundamental understanding of key microbial species within such processes is important throughout the lifetime of their operations. Quantitative analysis of the active microbial communities during the cultivation of a mesophilic culture is reported in this study. Cell concentration and microbial community changes were measured and analyzed over 6 weeks of culture maintenance with a fresh medium. It was observed that a culture previously dominated by Leptospirillum ferriphilum was dominated by Ferroplasma acidiphilum and Acidiplasma cupricumulans species after 2 weeks, while Thermoplasmatales sp. and Cuniculiplasma divulgatum dominated the culture for the remainder of the 4-week of operation. The observed decrease in biomass concentration corresponded to the resultant decrease in ferrous-ion oxidation during the maintenance period. This shift in the microbial community structure was thought to be catalyzed by the constituent of the medium, which is indicative of the microbial adaptability of the individual strains in the culture to changes in the medium composition. Thus, this study may provide insight into the activity of these microbes to better harness their functionality by changing process conditions. This understanding may help in overcoming potential technical challenges associated with the processing of low-grade and complex ores due to microbial dynamics.

Stibnite (Sb2S3) is the predominant form of the antimony (Sb) in nature and the main component of antimony tailings. The process of biodissolution of stibnite under neutral or alkaline conditions is one of the most prevalent geochemical processes of antimony release. Recent studies have shown that microorganisms such as Acidithiobacillus (A.) ferrooxidans can promote the biodissolution process of stibnite under extreme acidic conditions, but the process is affected by other substances in the environment, such as its associated minerals pyrite (FeS2) and arsenopyrite (FeAsS). Therefore, this study is devoted to investigating the mechanism of influence pyrite (FeS2) or arsenopyrite (FeAsS) on the biodissolution of stibnite. Through the analysis of environmental physicochemical properties, mineral surface morphology, elemental morphology transformations, electrochemistry, transcriptomics, and molecular morphology simulations, we found that: (1) the presence of FeS2/FeAsS can promote the biodissolution process of stibnite, accelerate the oxidation of Sb and sulfur (S); (2) A. ferrooxidans can enhance the electrochemical activity of the surface of the associated minerals; (3) the expression of functional genes of A. ferrooxidans has increased with the presence of associated minerals, such as electron transfer and metabolism-related functional genes. These results prove the presence of the associated minerals could accelerate the process of antimony release and elucidate the mechanism of stibnite dissolution mediated by the role of pyrite/arsenopyrite-A. ferrooxidans, which are of great theoretical significance for understanding the geochemical cycle of antimony in sulfide mining areas and for the development of antimony pollution treatment and remediation technologies.

In this study, we investigated an innovative bioleaching process that aims to improve the leaching performance of chalcopyrite by in situ mechanical abrasion of passivating layers. This technology uses millimetre-sized grinding glass beads to erode particles continuously, thereby applying shear stresses that continuously remove and refresh surface layers. To this end, a hybrid bioreactor (6 L) was constructed with a stirred mill impeller to perform bioleaching and attrition concomitantly inside a single reactor. Bioleaching tests were carried out with a Cu concentrate containing 71% chalcopyrite and the BRGM-KCC bacterial consortium. Using a fixed glass beads charge in all experiments, slurry solids concentration was set to either 10 wt% or 5 wt%, corresponding to concentrate/beads (C/B) mass ratios of 1.25 and 0.625. With a C/B mass ratio of 1.25, bacteria were strongly inhibited. With a 0.625 C/B mass ratio, microbial activity and growth were observed after a latency phase of 6 days. At the end of the test, Eh was close to 840 mV (SHE), and Cu yield reached 80%, versus 10.5% in conventional bioleaching STR tests. These results show that (i) microbial growth and activity are possible in an intense attrition-induced shearing environment, (ii) attrition allows chalcopyrite dissolution to continue when Eh exceeds the passivation threshold.

Responsible sourcing and processing of critical minerals is the key to effective energy transition. The current traditional extraction of rare earth elements (REEs) from REEs-bearing minerals is carbon-intensive, uses harsh chemicals, and produces a large amount of toxic waste. Therefore, the need for sustainable development of innovative flowsheets to assist the mining industry in extracting REEs with a lower carbon footprint is expected to grow rapidly. To address challenges in conventional biomining due to high levels of salts in process waters, refractory, and low-grade mineral ores/wastes, this study aimed to understand the role of salinity and iron/sulfur (Fe/S) oxidation in monazite bioleaching systems. The results showed that microbially driven dissolution of REEs using the native microbes on non-sterile ore was affected by both the availability of Fe/S as well as increased salinity. The consortium of indigenous microbes on the ore dissolved REEs (Ce, La, Nd, Pr, and Y) up to a final concentration of 40 and 54 mg/L in the presence of 30 and 15 g/L Cl− (as NaCl), respectively.

Rare earth elements (REEs) are crucial components in clean energy, electronics, and national defense applications. The demand for more has led to the exploration of alternative REE sources, such as groundwater. In this study, we use REE-selective Bacillus subtilis spores due to their unique adsorptive/desorptive capabilities to extract REEs from the solution. The adsorption process was investigated at different experimental parameters such as pH and initial metal concentration using both groundwater and standard REE spike solutions. Interferences in the groundwater, such as iron and aluminum, have proven to limit the adsorptive capabilities of the spores. The standard Dy solutions demonstrate recovery of 95% Dy3+ using the spores. The groundwater results indicate that none of the seven target REEs were precipitated at pH 4.1 (Fe oxidation), but 50% of Fe and Al were removed. Increasing the pH to 6.1 (Al oxidation), only 2% of Fe and Al remained, while 75% of REEs were lost. Removing interferences led to substantially higher adsorption percentages. These adsorption pH studies demonstrated pH 7 as having the highest adsorption percentages. The spores efficiently adsorbed the seven target lanthanides at 97%, while recovery was ˃90%. There was a stronger binding for Nd, La, and Y but at different pHs. The overall findings suggest that groundwater has the potential to be a viable source of REEs, and this biological adsorption system can be used to extract REEs from various sources.

Phosphorus (P) is an essential macronutrient in agriculture and has been listed as a critical raw material by the European Commission given its high demand and unequal distribution of phosphate rock reserves. In addition, crops can absorb a small part, and excess P fertilizers are washed away, resulting in eutrophication. Therefore, efforts must be made for the development of slow-release P fertilizer that can be absorbed effectively by crops. The objective of this study is to evaluate the slow release of P, converting insoluble phosphate to soluble forms. For this, grown cells of the acidophilic sulfur-oxidizing Acidithiobacillus (At.) thiooxidans were harvested to obtain a suspension with ~109 cell/mL, which were encapsulated in a matrix of alginate (3%) with CaCl2 (4%) together with elemental sulfur (0.4%) and Ca3(PO4)2 (0.25%). Beads with an average diameter of ~3 mm each were obtained and inoculated to a shake flask of 500 mL in triplicate; each containing 200 mL autotrophic basal salts with trace elements, and cultivated aerobically at 30 °C, shaken at 100 rpm for 21 days. Three initial pH were evaluated (2.0, 2.2, and 2.5). Samples were withdrawn at regular intervals to measure the soluble phosphate and sulfate. The results have confirmed the slow release of bioavailable phosphate by using At. thiooxidans encapsulated on the beads of alginate compared with experiments carried out with the suspension cells. This study opens new avenues for biotechnologies to dissolve insoluble sources of phosphate such as apatite to be applied as slow-release P fertilizer.

In our work, density functional theory (DFT) is used to investigate the multiphase interface interactions between metal sulfide minerals and iron/sulfur-oxidizing microorganisms. The DFT results reveal that during the sulfide ore bioleaching process, the thermodynamically preferred adsorption site for bacteria is the Fe site, μ-S0, and Fe(III)-6H2O can promote the dissolution of minerals, and the electron transfer is from CuFeS2 or Sb2S3 to FeS2. This research reveals the multiphase interface interaction mechanisms during the bioleaching process and provides a theoretical basis for the industrial application of metal sulfide ore bioleaching.

In this research, two different jarosites generated by biological (bio-jarosite) and chemical (chem-jarosite) methods were used to study the uranium (U) removal efficiency and adsorption mechanism. The results showed that the maximum removal rate of U by bio-jarosite reached 77.4% and the U loading capacity was 43.4 mg/g, while the maximum removal rate was 67.2% and loading capacity was 33.6 mg/g for chem-jarosite under shaking conditions. SEM results showed that the surface of bio-jarosite is rougher than chem-jarosite, indicating a greater number of active sites were exposed on the bio-jarosite surface. Morphology would be one of the reasons why bio-jarosite has higher uptake capacity than that of chem-jarosite. These findings indicate that biogenerated jarosite is a great adsorbent for U remediation, but it was affected by bioleaching bacteria and pH. In addition, the bioleaching bacterium Sulfobacillus thermosulfidooxidans shows good potential as an adsorber of uranium.

Our study aimed to assess the influence of the design of shake flask experiments on the growth of At. ferrooxidans using elemental sulfur (S0) as substrate. Cultures of At. ferrooxidans in 0Km medium with 1% sulfur were incubated at 30 °C for 10 days. Different culture volumes (75–150 mL), agitation rates (101–350 rpm), and orbital diameters (19–25 mm) were used to vary the gas–liquid mass transfer coefficient (kLa, from 8 to 41 h−1) and the power dissipation per unit of volume (P0/V, from 21 to 982 W/m3) from one culture to another. At. ferrooxidans growth and S0-biooxidation rate were improved with the increase of kLa and P0/V. In all experiments, dissolved oxygen concentration remained above 85% of saturation, indicating that there was no limitation of the gas–liquid mass transfer. Increasing P0/V for a given value of kLa improved the growth rate while it remained the same for a fixed P0/V and different kLa. It was also observed that μmax reached a plateau when P0/V was above 600 W/m3. Interestingly, at the plateau, the agitation rate was higher than the theoretical critical rate Nc required to achieve a complete suspension of the sulfur particles, which was not the case for the other cultures. These results show that microbial growth of At. ferrooxidans on S0 was influenced by particle dispersion and not by gas–liquid mass transfer. In this case, P0/V and Nc are two key factors that must be considered in the design of the experiments.

The use of lithium-ion batteries (LIBs) has been increasing, and effective recycling strategies need to be developed. Bioleaching, which uses microorganisms to solubilize metals, is a promising, environmentally friendly alternative to conventional (pyro- and/or hydrometallurgy-based) metal recovery techniques. However, bioleaching has not yet been applied to recycle LIBs on an industrial scale. A low-waste closed-loop bioleaching-based technology was developed for cobalt (Co) recovery from an active cathode material (LiCoO2; LCO). The system involved generation of sulfuric acid in an acid-generating bioreactor (AGB) containing an adapted acidophilic prokaryotic consortium, 2- to 3-week leaching of LCO with the biogenic acid (pH 0.9), selective precipitation of Co hydroxide, and recirculation of the raffinate back into the AGB. In total, 58.2% and 100% of the Co and Li, respectively, were solubilized in seven phases, and >99.9% of the dissolved Co was recovered after each phase. Additionally, Co electrowinning was optimized as an alternative recovery technique, yielding high recovery rates (91.1% and 73.6% on carbon felt and roughened steel, respectively) from bioleachates that contained significantly lower Co concentrations than industrial hydrometallurgical liquors. The closed-loop system was dominated by the mixotrophic archaeon Ferroplasma, followed by the sulfur-oxidizing bacteria Acidithiobacillus (At.) caldus and At. thiooxidans. The developed system achieved high Co recovery rates and provided high-purity solid products suitable for a battery supply chain while minimizing waste production and the inhibitory effects of elevated concentrations of dissolved metals on the leaching prokaryotes. The system is suitable for scale-up applications and has the potential to be adapted to different battery chemistries.

Microbial communities play a significant role in the treatment of inorganic constituents at mine sites, often through direct metabolic reduction. Targeted quantitative polymerase chain reaction (qPCR) allows for quantitative monitoring of specific genes, whereas next-generation sequencing (NGS) can be used to provide comprehensive microbial community profiles that are used to monitor important metabolic functions. In this study, qPCR tests, NGS, and differential plating methods combined with genetic colony identification were used to detect and characterize microbial communities that reduced selenate (SeO42−) to selenite (SeO32−) or SeO32− to elemental selenium (Se). This combination of novel and classic molecular biological tools provided multiple lenses to view selenium metabolizing communities and can increase our ability to understand how microbiology impacts treatment processes for selenium.

The increasing demand for critical metals, such as nickel (Ni) and cobalt (Co) in the production of batteries needed for electric vehicles (EV), has warranted the need to explore alternative technologies capable of valorizing tailings and waste materials as potential additions to the critical metals supply chain. Pyrrhotite tailings often entrain Ni and Co in mineral matrices amendable to bioleaching. To be economic and sustainable, the process needs to include the recovery of Ni and Co but also the recovery of the major iron (Fe) and sulfur components, work to reduce any waste by-products, as well as support repurposing. Conventional bioleaching of pyrrhotite-rich tailings at pH ≤ 2 requires great amounts of sulfuric acid, and the removal of Fe from the produced metal-rich liquor needs significant amounts of limestone or lime, leading to the generation of large volumes of sludge containing gypsum and ferric oxyhydroxides (which presents solid handling challenges), with the risk of co-precipitation of a portion of the target metals prior to recovery. In collaboration with CanmetMINING, this study investigates the piloting of a bioleaching approach proposed to treat the Sudbury basin pyrrhotite tailings stockpiles. The initial efforts to create a larger-scale piloting circuit allow optimization of operating parameters, which could help resolve the challenges associated with the implementation of a continuous pyrrhotite bioleaching process and make the process viable for industrial applications.

In previous investigations to treat acidic As(III)-containing solutions, an autotrophic acidophilic arsenite oxidizer, Acidiphilium acidophilum CJR1, has been isolated. Nonetheless, its physiological response toward As(III) remained unknown. An RNA-Seq approach was employed to obtain more insight. Though capable of autotrophic growth with arsenite, due to considerably better growth in the presence of yeast extract, A. acidophilum CJR1 was cultured under two heterotrophic conditions, one with additional arsenite and as a control one with yeast extract and 20 μM Fe2+. The results indicated the expression of arsenite oxidase genes under both conditions, suggesting that the enzyme may be constitutively expressed. In the As(III) condition, the COG categorization indicated that most strongly upregulated genes were energy-related or chaperones. These results provide the first transcriptomic insight into the arsenite response of an Acidiphilium acidophilum strain.

There are over 8500 mine tailing storage facilities with the gross weight of 282.5 billion tons. These are waste dumps with less value and have been ignored for a while. The operating and maintenance costs of those facilities are not small, and they can be huge liability issues when a failure happens. It can be an environmental disaster and a huge negative impact to the company’s operations and social responsibility. However, it could be an opportunity to extract more metals. A few copper mine tailings have been tested using conventional mineral processing followed by bioleaching/biooxidation of sulfide concentrates. Metals associated with sulfides were upgraded up to 13 times, and the concentrates were microbially oxidized to extract from sulfide matrix. A mixture of mesophilic microorganisms was used for bioleaching. The extraction efficiency of metals was up to 93% from the concentrate. The ultimate goal is to eliminate all tailings produced by the metallurgical operation, and a holistic approach for mineral processing, chemical/biological metallurgy, water treatment, and value-added structural material fabrication has been investigated. A detailed flowsheet of the Entail Process™ was developed showing the benefits of using microbial treatment by biohydrometallurgy. One of the new processes is to fabricate value-added product called Geofoam™. Other than conventional geopolymerization, geofoam shows many physicochemical characteristics that can be used in different applications.

This study explores biohydrometallurgical techniques within the carbon capture, utilization, and storage (CCUS) framework to address global CO2 emissions. A key aspect of this research involves utilizing the bacterium Proteus mirabilis strain SKC-7 for bioleaching steel slag, resulting in a calcium-rich pregnant leach solution (PLS) suitable for CCUS applications. The study rigorously examines the impacts of various parameters on the formation of carbonate precipitates within the CCUS framework. These parameters include the incorporation of carbonic anhydrase enzymes (found in the spent medium), the adjustment of pH levels, and the modulation of CO2 gas flow rates. Initially, the bioleaching of steel slag was conducted to generate the calcium-rich PLS, followed by carbon sequestration experiments using the bacterium Bacillus subtilis strain SKC-14. These experiments involved injecting CO2 into a combination of PLS and spent medium, after which the precipitates were analyzed for calcium conversion percentages. The characterization of these precipitates was conducted using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). Key findings included high calcium conversion rates under various experimental conditions and the identification of diverse carbonate precipitate morphologies, including natron and the vaterite polymorphs of calcium carbonate. The study demonstrates the effectiveness of biohydrometallurgical methods in advancing CCUS technology, presenting a viable solution for mitigating global warming and climate change. To the best of our understanding, this study represents the initial documented application of biohydrometallurgical processes in the context of CCUS.

Nitrogen is a macronutrient, and, in its ammonium form, it is easily assimilated by most microorganisms. For assessing the effect of NH4+ in bioleaching environments, we designed column tests in both suitable and stressed conditions—specifically, low temperatures and inhibitory sulfate concentrations. We observed differential effects between suitable and stressed environments. The addition of NH4+ generated a significant increase in the total bacterial number and a slight increase in the oxidation activity in a suitable environment. The cease in NH4+ amendment has a higher impact on the archaea compared to the bacterial population. This interruption in NH4+ feeding also impacted the ferrous iron oxidation activity. Based on the gene expression analysis, we realized that the nifH gene was overexpressed by Leptospirillum at NH4+ levels lower than 10 mg L−1. Moreover, in bioleaching columns at low temperatures, the total bacterial and archaeal cell numbers depended on the NH4+ levels. Higher NH4+ levels in those columns enhance the Most Probable Number (MPN) of Fe-oxidizing microorganisms and the oxidation activity; therefore, the lag phase in the Eh increase was shorter and the Cu recovery higher. The redox potential decreased in the pregnant leaching solution (PLS) of the column after the turn-off of NH4+ feeding. The ion concentration in 9 m columns supplemented with 40 mg L−1 of NH4+ decreased from 37 to 5 mg L−1 after 50 days of amendment cease. In column tests, at high sulfate concentrations, the NH4+ amendment significantly increases microbial activity and Cu recovery.

Acid rock drainage (ARD) is a serious environmental risk that reduces the pH of water resources, contaminates ecosystems, and is caused by the oxidation of mine waste exposed to natural elements. Previous studies have shown great promise in preventing ARD using co-disposal and microbially-induced calcite precipitation (MICP). Oxidant ingress is limited in traditional co-disposal, but when combined with MICP, it is decreased significantly. In addition, calcite increases the neutralization capacity and leads to metal immobilization, further limiting environmental damage even under highly aggressive conditions. The main reagent-intensive step is the cementation phase in the MICP process, which involved daily irrigation of cementing solution made up of media, urea, and calcium chloride. In this study, the calcite yield was determined in co-disposed coal waste columns using various irrigation protocols. Two sets of 12 bioreactors were set up with different packing configurations where they received cementing solution every 4 or 7 days for 60 days. The calcite content was determined thereafter and compared to the calcite content found in co-disposed beds that received daily irrigation. Acid wash tests revealed that more frequent irrigation led to higher calcite content. However, the relative yield was not substantially different, and using an irrigation protocol where cementing solution is only applied weekly led to appreciable calcite formation that is thought to be sufficient for ARD prevention. Future studies should involve stress testing the weekly irrigated MICP-co-disposed beds to determine their long-term stability under aggressive acidic conditions compared to that of the successful daily-irrigated beds.

To achieve successful mine closure and restore derelict land, implementation of sustainable mine-site rehabilitation schemes aligned with circular economy principles should be prioritised using proactive strategies. To address both the need for fertile topsoils for mine-site rehabilitation and the desire to re-purpose benign mine wastes towards materials of value, an effective approach towards controlled resource management based on waste valorisation involves using the major coal ash fraction of coal waste to fabricate a soil (referred to as a technosols, FabSoil) by amending it with a suitable organic waste source. This technosol can be developed as a topsoil to remediate the degraded mine land. This study investigated the improvement of the fertility of the technosols, previously reported as FabSoil, through bioaugmentation and biostimulation. The FabSoil was fabricated from ultrafine coal tailings, inoculated with commercially available microbial inocula and amended with three different amounts of malt residue (2.5%, 5%, and 7% w/w) from a local brewery. Eragrostis tef (teff), a first-stage plant species, was grown in each of the treatments. The results indicated bioaugmentation of technosols amended with 5 wt% malt residue presents a favourable condition for the development of primary species used in site rehabilitation. This is expected to accelerate the establishment of self-sustaining fertile soils for the rehabilitation of disturbed mining areas.

To achieve effective bioleaching of base metals from PCBs, a balance of the rates of regeneration of ferric lixiviant and ferric reduction for leaching is required. We investigate the effect of Fe2+ concentration, PCB solid loading, and operating mode in a novel two-stage bioleaching reactor system comprised of a stirred tank reactor for Fe3+ leaching of base metals in PCBs, coupled to a packed-bed reactor with biomass retention for microbial Fe3+ regeneration. The packed-bed component consisted of multiple column reactors in series, each packed with polyurethane foam biomass support particles colonised with mixed copper-adapted mesophilic cultures of Leptospirillum ferriphilum, Acidithiobacillus caldus, and Acidiplasma cupricumulans. Enhanced tolerance to metal ions and protection offered by biofilm associated with colonised cells are used to maintain high microbial ferrous oxidation rates. The initial Fe2+ concentration was varied from 5–10 g/L, and PCB loading was varied from 0–20% w/v. Two operation modes were explored: (1) a fully closed-loop system where a metal ions-rich stream was re-circulated between the chemical and packed-bed bioreactor, and (2) an open system with part of the metal ion-rich stream re-circulated and part recovered for continuous metal recovery. At each reactor configuration studied, the Fe3+ reduction rate as a function of metal dissolution was compared to that of microbial Fe3+ regeneration rate. With the microbial Fe3+ regeneration being the rate-determining step in bioleaching, optimum reactor configuration for maximum delivery of the required Fe3+ oxidant is vital to maximise the space-time yield of the bioleaching to optimise overall bioleaching efficiency.

This study aims to evaluate the feasibility of an integrated remediation strategy for a mine site presenting both historic mine waste dumps and AMD. A microbial consortium from an SRB bioreactor treating a real AMD using glycerol as an electron donor was adapted to grass compost as the sole energy source. It was then used as inoculum to assess the feasibility of treating the AMD of the studied site with compost as an energy source: increasing pH and precipitating metals (Fe, Co, Ni), and arsenic. The first experiments using garden grass compost showed a slow but effective reduction of sulfate (800 mg/L in one month) and validated the ability of the SRB consortium to use grass compost as an energy and carbon source in the presence of AMD containing 200 mg/L Fe and presenting acidic pH (pH 2.5). Subsequent experiments aim to test compost obtained with the aerial parts of plants from an onsite phytostabilization pilot plot. The following parameters will help determine the efficiency/feasibility of the approach: mass balance of metals, arsenic, carbon, and sulfur in liquid and solid phases.

Cobalt, crucial for lithium-ion batteries and various other industries, experiences increasing global demand, notably for electromobility. Chile’s copper production offers a chance to produce cobalt as a by-product, complementing its lithium and cobalt mining sectors, pivotal for the transition to clean energy technologies. Bioleaching, utilizing microorganisms for metal extraction, shows potential for cobalt production, supported by Chile’s expertise in sustainable technology R&D, particularly in copper bioleaching. This project, led by researchers with profound experience in bioleaching and geology, the first bioleaching results at flask level are presented using a native consortium of thermotolerant microbes, adapted to operate at on-field conditions using a cobaltiferous pyrite enriched tailing extracted from the north of Chile. Two microbial consortia were isolated and selected at 30 and 45 °C for its astonishing capacity oxidizing iron and sulfur, the main ability for dissolving pyrite (FeS2), the principal bearing ore containing cobalt. Genomic characterization of both consortia is undergoing. The four-year project aims to scale up bioleaching processes, focusing on reprocessing cobalt-rich tailings from copper mines in the Atacama and Coquimbo regions, particularly those of the iron oxide-copper-gold (IOCG) type. Beyond extracting value from tailings, the project carries significant environmental benefits by intercepting pyrite early in the process, it mitigates the environmental threat of acid mine drainage (AMD). Preventing AMD not only safeguards water resources and agricultural land from contamination but also mitigates risks associated with tailings dam destabilization. The project not only promises economic gains but also underscores Chile’s commitment to sustainable resource management and environmental stewardship.

Critical elements, such as rare earths, gallium, and germanium, are becoming increasingly important to the global economy due to the advancement of alternative energy and electronic technologies. Australia produces an estimated 30 million tonnes per year of alumina refinery waste (red mud), which contains an array of critical elements. Biomining could be the key to harnessing this untapped critical element supply, as current chemical separation methods are costly and environmentally damaging. This approach relies upon using identified microorganisms with a prior demonstration of critical element utilisation and the presence of these species across various mine waste sites. Candidate microorganisms include Pseudomonas putida, Shewanella oneidensis, Geobacter metallireducens, and Aspergillus niger. This study aims at identifying the Ga, La, Dy, and Ge binding capacities of P. putida and the proteins related to critical metal metabolism using bioinformatics and “omics” research. Initial proteomics analyses have identified 153 statistically relevant proteins associated with Ga interactions, including transcriptional regulation proteins associated with arsenic metal tolerance (ArsR1 and ArsH) and proteins previously identified as having metal-binding capacity. These include pyrroloquinoline quinone (PQQ) dependent alcohol dehydrogenases, which have previously demonstrated lanthanide dependence and binding capability. These proteins will be produced and tested for their potential use as biomaterials to recover Ga, which will pave the way for developing a sustainable method to recover this highly demanded element. This research could be used as a platform to create novel sustainable biomining solutions for the valorisation of alumina refinery waste.

The ongoing global transition towards the development of greener technologies, along with a focus on reducing carbon emissions and environmental footprints, has prompted the mining industry to pursue greener alternatives. Bioleaching is a cost-effective and environmentally friendly technology that can be an appropriate alternative. At present, bio-oxidation of metals from ores is successfully practiced in industries; however, there is currently no bio-based process for the extraction of precious metals. Therefore, we aimed to develop a complete biological process for bioprocessing UG-2 PGM ores. The first part of the study involved bio-pretreatment to remove base metals from ores, followed by cyanogenic bioleaching of the pre-treated material. Microorganisms indigenous to a South African platinum mine were isolated and screened for their ability to produce biogenic cyanide. Four bacterial strains, namely Pseudomonas aeruginosa, Pseudomonas stutzeri, Pseudomonas brassicacearum, and Bacillus sp., exhibited significant bio-CN-producing capability. Among these strains, under optimized conditions, P. brassicacearum demonstrated the highest bio-CN production (14 ± 1 mg/L) at 18 hours of growth. Compared to one-step bioleaching, two-step bioleaching yielded higher mobilization of metals. Additionally, the two-step bioleaching approach was found to give higher precious metal recoveries from pre-treated material as opposed to untreated material. Amongst all bacterial strains, P. brassicacearum showed the highest metal extractions, i.e. 75.69, 18.69, 9.38, and 0.28% of Au, Pd, Rh, and Pt, respectively, at 10 g/L pulp density. The findings are encouraging and have established the foundation for creating a complete bio-based method for PGM bioprocessing from UG-2 ores.

Planetary Technologies, Inc. is developing technologies that process various source materials for the end goal of carbon dioxide removal through ocean alkalinity enhancement (OAE). One such technology that has been developed processes asbestos tailings with sulphuric acid solution, recovering magnesium as well as nickel and cobalt in the leach liquor. Leaching was conducted in 3 m and 5.5 m height columns with varying lixiviant flowrates (derived from the irrigation rates) to study heap leaching efficiencies after 100 days. Two more columns of 3 m were loaded with feed, and a load of 300 kg applied to the top of the heap to simulate leaching at 9 m height to observe if this affected physical and/or chemical performance of the leach. Two different flowrates were studied, and these tests yielded higher metal extractions. The optimized leaching efficiencies were 93%, 92%, and 89% for Mg, Ni, and Co, respectively. Furthermore, the 25% asbestos content of the feed was reduced to non-detectable in the leach residue. The resulting pregnant leach solution was collected and contacted with fresh feed to consume the excess acidity. The pH-adjusted discharge solution was treated with reagents to precipitate Fe, Al, and other impurities before a high-grade mixed hydroxide precipitate of up to 30.5% Ni was produced in a two-stage counter-current precipitation sequence.

This chapter investigates the effectiveness of long-term and accelerated sulfuric acid soaking processes for the extraction of rare earth elements (REE) from a Canadian ore sample with neodymium (Nd) in allanite and dysprosium (Dy) in fergusonite. Both soaking-cracking processes were followed by water leaching for 1 to 4 h. The long-term soaking process, conducted at ambient temperature for periods ranging from 1 to 6 months, achieved 78% TREE recovery. The accelerated soaking process, conducted at 90 °C for periods ranging from 1 to 4 h, achieved over 73% TREE recovery. The metallurgy performances of these processes were compared to those from the conventional acid baking water leaching process. The results indicated that these acid soaking processes can liberate and recover REE from allanite and fergusonite host minerals, providing a potential alternative to the conventional rotary kiln acid-cracking process. This effort could lead to reductions in capital and operational costs, as well as improvements in environmental and carbon emission ratings.

A commercial hydrometallurgical plant has been operating in Napanee, Ontario since 2008 leaching superalloy scrap with aqua regia and producing a high-grade tantalum/tungsten leach residue, a mixed nickel/cobalt hydroxide cake, and high-purity ammonium perrhenate as final products. The process involves batch leaching of crushed superalloy scrap followed by pressure filtration to produce a leach liquor containing rhenium, nickel, and cobalt and a leach residue that is high in tantalum and tungsten, which is sold. The leach liquor is neutralized in stages with soda ash and caustic soda to ~pH 10 to precipitate a mixed nickel/cobalt hydroxide cake, which is recovered by pressure filtration and sold. The rhenium pregnant leach solution is then processed by anion exchange with a strong base resin to extract and concentrate rhenium. Rhenium is stripped from the resin with strong ammonium thiocyanate solution, and the strip liquor is further concentrated by evaporation and freeze cooling to precipitate ammonium perrhenate. This paper will present results from the various unit operations and describe the many changes that have been implemented over the years to improve process efficiency, reduce operating costs, and improve the ability of the plant to handle diverse feeds.

This research focuses on selectively precipitating impurities, namely aluminum, iron, and thorium, from a pregnant leach solution (PLS) rich in rare earth elements (REEs). The main aim is to remove these impurities while retaining the maximum possible REE in solution, a vital step in REE processing. The study combines experimental work with modeling to decode the complex precipitation patterns. A design of experiments and response surface methodology are employed to evaluate how temperature, pH adjustment (using 20 wt% magnesium carbonate (MgCO3)), and oxidation using hydrogen peroxide (H2O2) affect impurity removal and REE preservation. Characterization of the resulting solid precipitates is performed using X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). Analysis shows that precipitates at pH 3 and 5.5 mainly comprise ferrihydrite, aluminum sulfate, and magnesium carbonate. EDX also reveals REEs in these precipitates. This research sheds light on the process of selectively removing impurities from REE solutions and lays a foundation for enhancing REE recovery, thus supporting sustainable and cost-effective production of these essential materials. The findings inform the development of more effective and environmentally benign REE production methods, crucial for many high-tech applications. Further studies and process enhancements based on this work could improve REE recovery efficiency, meeting the growing industry demand for these materials.

Seabed polymetallic nodules, which contain significant quantities of metals key to electrification (nickel, cobalt, copper, and manganese), can be processed using a variety of different metallurgical processing routes, including direct smelting and subsequent hydrometallurgy, ammoniacal leaching (gas reduction or Cuprion), or acid leaching (often reductive). Many of these approaches suffer from reduced cobalt extraction, difficult physical performance, or just general overall circuit complexity. SGS has considered pressure acid leaching of nodules for further investigation, as publicly shared data on this processing route stems from the 1970s and 1980s and is not always easily accessible. This paper will detail the series of tests conducted and the results obtained (high Ni/Co/Cu recovery with limited Mn/Fe), as well as comment on the potential treatment options for the product solution and residue.

The Lofdal REE project is one of the few rare earth deposits in the world that contains mostly heavy rare earth elements (~75% HREO distribution). The mineralogy of the Lofdal project is complex, with xenotime as the primary rare earth hosting mineral and silicates, calcite, and iron oxide as the main gangue minerals. The beneficiation flowsheet developed for the Lofdal project in previous studies was further optimized on the run of mine samples and piloted at SGS Canada. The flotation pilot plant produced a ~93 kg concentrate sample for further optimization and scale-up testwork of the hydrometallurgical steps to recover the HREE from the concentrate. This paper provides an update on the laboratory testing programs conducted to develop the process.

The global market for lithium products is very attractive with the supply of raw materials falling behind the emerging demand growth in markets such as China. This paper examines the growing number of lithium conversion plants to produce battery-grade lithium hydroxide or carbonate. These are complex chemical plants with very high capital costs. For several conversion projects, the feasibility study projected CAPEX and OPEX had been far exceeded during the development. Projects ramp up had been slow, taking around 24 to 36 months to achieve the requisite battery-grade (4 N) specifications of the products as well as plant throughput and reliability. This paper references several projects—without identifying them—and lessons learned. Several projects made mistakes and bad decisions with fast tracking and efforts to reduce capital resulting in poor quality equipment; all of which have led to increase in operating costs. Whilst generally, the ore preparation including the acid roasting and leaching steps, which are standard technologies, have proven to be operable, the multi-stage crystallisation and re-leaching steps are proving to be problematic. The softening in lithium prices during 2023 has exacerbated some of these problems. Mergers and takeovers in the industry are occurring. In the longer term, a strengthening of the prices will see a different industry emerge.

The Metals Company (TMC) is pioneering a new source of critical minerals needed to scale up battery production and energy storage globally. A vast resource of nickel, copper, cobalt, and manganese is contained in polymetallic nodules that sit unattached on the seabed, four kilometers below the surface in an area of the Pacific Ocean called the Clarion Clipperton Zone. TMC’s flowsheet to produce these metals from the nodules involves initial pyrometallurgical processing to produce a nickel-copper-cobalt matte, which is further refined to battery-grade sulfates and copper metal using a conventional hydrometallurgical process. This paper provides an overview of the project, the hydrometallurgical flowsheet, and the associated outcomes from a bench-scale testing program undertaken at the SGS laboratories in Lakefield, Ontario. The hydrometallurgical flowsheet being developed is based on existing processes used commercially for treating platinum group metal-containing matte. It consists of a multistage leach process that produces a nickel-cobalt liquor with low copper, which is further refined into separate nickel and cobalt streams to produce high purity, battery-grade sulfate crystals. The process also produces a copper-rich liquor that feeds copper electrowinning for the production of copper cathode. This multistage leach process includes both atmospheric and pressure leaching and was demonstrated to achieve greater than 99% extraction of nickel, cobalt, and copper from the matte. Both the nickel and cobalt sulfate specifications will be presented and will show that the achievable purities of these products are comparable to those observed in present market battery-grade sulfates.

The sulfuric acid bake followed by water leaching is now well-established technology used for processing of ores and concentrates containing rare earth phosphate mineralization. Gangue minerals can have a significant impact on the process. In this work, we tease out the impact of the presence of iron minerals on the monazite acid bake process, focusing particularly on magnetite. Sulfuric acid baking and leaching of a magnetite sample alone and a magnetite/monazite mixture at bake temperatures ranging between 200 and 800 °C was conducted. The presence of magnetite with monazite had a significant impact on the extraction of rare earth elements and impurities from monazite and these were explained by the phases formed in the bake.

This extended abstract is based on a recently published paper by Umicore (Van Hoof G, Robertz B, Verrecht B, Metals 13:1915, 2023). Electric mobility requires a lot of critical raw materials like nickel, cobalt, and lithium. Recycling these materials from end-of-life batteries and production scrap is key for a sustainable and circular battery value chain. We present a carbon footprint analysis of two battery recycling flowsheets: Pyro-Hydro, a combination of battery smelting followed by further hydrometallurgical refining of the alloy, and Thermomechanical-Hydro, a combination of (thermo)mechanical pretreatment and further refining of the resulting black mass via hydrometallurgy. The analysis is based on a prospective life cycle assessment using primary data from engineering models and reflects the current state of the art. The results show that Pyro-Hydro leads to the lowest overall carbon footprint, but both flowsheets have challenges and opportunities for decarbonization (Neuman et al. Adv Energy Mater 12:2102917, 2022). The analysis also highlights the importance of accurately assessing the fate of the side streams, such as graphite and electrolyte, to gain a complete and objective view.

Fluidized beds heated via fossil fuel combustion have been widely used for various applications, including mineral processing. Heating these fluidized beds with clean electricity is emerging as a promising solution to reduce greenhouse gas emissions and improve energy efficiency, operability, and product quality. Various heating principles can be applied for electrically heated fluidized beds (EHFBs), including Joule heating, induction heating, electromagnetic irradiation, sonication, plasma heating, and gas preheating. Graphite purification is described as an EHFB case study.

This study evaluates the potential of a chemical soaking process as an alternative to the conventional acid baking process for cracking minerals hosting rare earth elements (REEs) and scandium (Sc). The research focuses on the extraction efficiency for Canadian REE/Sc ore/concentrate samples containing minerals such as allanite, fergusonite, bastnaesite, monazite, and pyroxene. Two soaking approaches were examined: a long-term acid/alkaline soaking process at ambient temperature lasting 1 to 6 months and an accelerated soaking process at 95 °C for 17 h or less. Following soaking, water leaching was conducted for 2.5 to 5 h. The long-term soaking achieved REE/Sc liberation ranging from 45% to over 90%, while the accelerated method demonstrated higher REE recoveries than the long-term soaking result for most samples. Although further optimization was not pursued due to the screening nature of this study, the findings suggested that chemical soaking could be a viable and environmentally friendly alternative to traditional methods for a wide range of REE/Sc bearing samples, potentially offering cost savings and reduced carbon emissions.

Mkango Resources Ltd. is developing the Songwe Hill rare earth carbonatite deposit in Malawi. The rare earth host minerals in the ore include synchysite (Ca(Ce,La,Nd)(CO3)2F), parisite (Ca(Ce,La,Nd)2(CO3)3F2) and fluorapatite Ca5(PO4)3F. The process development for the flotation concentrate was targeted at the particular mineralogy of the deposit and aimed to develop a flowsheet that would elegantly address the challenges relating to the simultaneous presence of phosphate, fluoride and calcium which complicated the recovery of rare earths downstream. This paper outlines the various process options evaluated including direct HCl leach, air roast/HCl leach, sodium carbonate roast/HCl leach and caustic conversion/HCl leach. A simple flowsheet was developed, which was later tested at pilot plant scale and successfully demonstrated high rare earth recoveries and formed the basis for a definitive feasibility study.

With the accelerated global transition to electrified transportation and increased use of electrical energy in multiple sectors, the need for storage of electrical energy in Li-ion batteries has massively increased. New sources of lithium from hard rock minerals, clay deposits, salar brines, and geothermal brines are being actively sought with increased lithium extraction plant capacity being planned, designed, and developed. Urgency now exists to significantly increase production of refined lithium chemicals of battery grade quality to meet the expected ramp-up in global demand for Li-ion batteries to supply electric vehicles and other markets. This urgent push to meet demand is driven overall by the need to reduce global CO2 gas emissions and limit rising temperatures in the earth’s atmosphere. However, despite this push, feed source chemistry and the requisite tailored processing approaches to achieve battery grade products for Li-ion batteries must first be fully measured, understood, and adequately tested, to develop viable and operable process flowsheets. Thereafter, rigorous, stage-wise engineering of a selected flowsheet still needs to be executed to provide the required engineering detail and accuracy with sufficient confidence in project timelines, and in capital and operating cost estimates. In this paper, key stages in executing front-end loading (FEL) engineering of projects are outlined and how the associated testing programs tie in. Rigorous completion of these stages is shown to be essential to adequately design and cost such lithium extraction projects to reduce operational and financial risks. A case example of a scoping study for a lithium refinery producing battery grade lithium chemicals is presented to illustrate flowsheet development, scoping level engineering, and to show some economic drivers for lithium plants. Elements from this scoping study illustrate important risks in developing lithium projects and highlight the need for adequate flowsheet development with stage-wise engineering to systematically lower the risk of process failures, design flaws, poor plant operability, and economic losses.

Graphite in both its mined and synthetic forms is the key component of the lithium-ion battery (LIB) anodes used in electric vehicles. On average 50–200 kg of hydrometallurgically refined graphite is used in the battery pack anodes for a single vehicle, accounting for more than 25% of the battery pack mass. The increased demand for production of electric vehicles in recent years has been accompanied by an additional interest in research and process development for purification of mined graphite. Production of high-purity graphite powder suitable for use in LIB anodes can be achieved by grinding and flotation of mined graphite followed by alkali digestion of the flotation concentrate and further grinding and flotation. At elevated temperatures, impurities such as quartz (SiO2), alumino-silicate minerals (present as feldspar and clays), various heavy metals, and iron (present as hematite) all react with alkali reagents like caustic soda and are separated from the mined graphite feedstock. This paper outlines the alkali leach hydrometallurgical options, when coupled with grinding and flotation, can result in production of a high-purity refined graphite product that meets the stringent specifications of electric vehicle LIBs. Challenges in materials of construction and equipment selection for the alkali leach process at high temperatures and pressures are also discussed.

This study explores the complex relationship between particle size, mineral composition, surface characteristics, elemental distribution, and the mechanisms of rare earth element (REE) adsorption in a unique ionic clay from South America. Differing from the common ionic clays that primarily exhibit physisorption, this sample demonstrates a mix of REE adsorption methods, including chemisorption. The research includes dividing the clay into three particle size groups: S1 (<0.25 mm), S2 (0.25–0.5 mm), and S3 (0.5–2 mm), and thoroughly analyzing each for elemental and mineral composition, surface area, morphology, elemental distribution, and REE absorption processes. The findings show that most REEs that can be desorbed are physisorbed, mainly due to kaolinite, which is generally associated with physisorption. Heavy rare earth elements (HREEs) are noticeably preferred in adsorption compared with light rare earth elements (LREEs), a pattern attributed to the weathering processes during the formation of the clay, promoting movement and concentration of HREEs. The ionic clay contains a significant amount of mineralized REEs, suggesting more intensive extraction methods like acid baking and water leaching for complete REE extraction. In terms of desorbable REEs, physiosorption is predominant, accounting for over 80%. Chemisorbed REEs are found in association with various minerals, including kaolinite, quartz, and goethite. This research reveals the detailed interaction between particle sizes, mineral makeup, surface features, and REE adsorption behaviors in a non-standard ionic clay sample, offering valuable insights into the factors influencing REE adsorption in ionic clays and highlighting the need to consider different adsorption methods in future extraction processes.

This study aims to develop a more efficient method for separating magnesium from nickel and cobalt in leach solutions, addressing the challenges of traditional metal separation techniques. Nickel and cobalt are vital for various applications, especially in lithium-ion battery production, but their extraction from low-grade laterite ores is complicated by impurities like magnesium. Magnesium’s presence is particularly problematic in solvent extraction processes used for nickel and cobalt separation, as it can degrade the performance of battery cathodes. The proposed solution employs ethylenediaminetetraacetic acid (EDTA) to selectively form complexes with nickel and cobalt, reducing their co-precipitation with magnesium. Through thermodynamic simulations and kinetic experiments at temperatures of 25, 50, and 75 °C, this study optimizes the complexation process. Results indicate that increasing the temperature accelerates complexation, enabling magnesium separation efficiency over 98% and reducing nickel and cobalt loss to below 2% at 75 °C. The research highlights the recyclability of EDTA, enhancing the method’s economic and environmental viability. This novel approach offers a significant advancement in metal processing for lithium-ion battery manufacturing, providing a viable alternative to conventional magnesium separation methods and setting a promising direction for further research in metal recovery and purification.

Ionic clays typically contain about 0.05–0.5 wt% of rare earth oxides (REO). In these clays, rare earth elements (REEs) are adsorbed onto the surfaces of aluminosilicate minerals such as kaolinite, illite, and smectite. The formation of ionic clay deposits is largely attributed to the in situ weathering of REE-containing rocks, like granitic or igneous rocks. This weathering process leads to the formation of aluminosilicate clays that capture solubilized REE ions. The primary method for extracting REEs from these ionic clays is through leaching with inorganic salt solutions that contain mono- or divalent cations. This leaching technique facilitates the desorption of physisorbed REEs, allowing these elements to be replaced by the cations in the leaching solution, and results in the REEs becoming soluble in the form of sulfates or chlorides. Some earlier studies have also employed pH adjustments to enhance REE extraction’s efficiency. In this specific study, a 20 g/L (NH4)2SO4 solution at a 1/3 g/mL solid to liquid ratio and a temperature of 25 °C is used to desorb REEs from an ionic clay sample. This study investigates the impact of varying agitation rates (from 150 to 700 rpm), pH levels (3–1), and particle size reduction (achieved through puck milling) on the extraction of REEs. The findings reveal that increasing the agitation to 350 rpm enhances REE extraction, while a decrease in pH marginally improves extraction efficiency. Additionally, reducing the particle size positively influences REE extraction, but it also raises the extraction of impurities like aluminum and thorium.

To overcome the inexpressive recycling rate (<1%) of critical raw materials (CRM) such as Ta from slags originating from the Cu industry, the enrichment of these metals in targeted minerals under specific conditions may facilitate the recycling. Based on that, our study investigated the mineralogy of Ta-rich phases in a synthetic fayalitic slag at different holding times in a specific transformation temperature, which was defined by thermochemical modeling. Laboratory scale samples of fayalitic slags mixed with Ta2O5 were smelted in an electric resistance furnace under argon atmosphere. Subsequently, the crystallization was achieved through cooling at a fixed rate of 25 °C/h to a specific temperature and held for different hold times. The samples were then removed from the furnace into air atmosphere and room temperature. The thermochemical modeling indicates that the oxidation of fayalite generates mainly magnetite (spinel) and silica, but also several other phases, such as pyroxene. The analysis performed on the samples was electron probe microanalysis (EPMA) and X-ray diffractometer (XRD), which showed that as the hold time increased, the individual crystals became larger and were distributed evenly throughout the sample. Moreover, the analyzed spinel phases were not directly associated with Ta-containing solidified phases. Rather, the metal exhibited preferential interaction with Ca-Si phases. In addition, the dissolution of Ta was observed in the last liquid phases, which were mainly Ca-Al-Si oxides. Prolonged hold times do not promote targeted Ta crystals nor control Ta mobility, but concentrate it in specific mineral phases which can allow further segregation.

Natural Resources Canada (NRCan)‘s Mineral Programs Branch (MPB), in collaboration with federal partners, is implementing a suite of programs to support the advancement of the Canadian Critical Minerals Strategy through a “technology pipeline” approach of extractive metallurgical processes from Fundamental Research to Research and Development to Pilot and Demonstration to Early Adoption. MPB’s suite of programs include the following: Critical Minerals Research, Development and Demonstration (CMRDD); Critical Minerals Geoscience and Data Initiative (CMGD); Indigenous Natural Resource Partnerships Program; Global Partnerships Program (GPI); and Critical Minerals Infrastructure Fund (CMIF). With a focus on the CMRDD program, the suite of federal government programs can support and advance critical mineral resource development. Emerging success stories resulting from federal government programs demonstrate the acceleration of critical mineral projects. Early-stage research and development projects, in which federal laboratories can provide collaborative or in-kind support, can advance mineral processing and metallurgical technologies through proof of concept bench scale testing that progresses the project to pilot scale. Piloting projects, which are eligible for CMRDD funding, encourages the demonstration of technologies that advance projects to commercialization. Commercialization projects can be supported by programs such as CMIF and Strategic Innovation Fund. The federal government’s “technology pipeline” approach can accelerate the advancement of critical mineral extraction from initial conception to commercialization, which supports and strengthens innovative mining ecosystems to position Canada as a stable supplier of critical metals.

The Strange Lake peralkaline rare earth deposit has an indicated resource of 189 million tonnes containing 0.934% total rare earth oxide (TREO). The ore is enriched in magnet rare earths; one tonne of ore contains 1.38 kg of Pr + Nd oxides, 0.05 kg of Tb4O7, and 0.35 kg of Dy2O3. The light rare earths are mainly hosted by parisite, allanite, and britholite, and the heavy rare earths by the silicate minerals keivite and britholite. Extensive testwork over the last 2 years has established that the ore is amenable to X-ray transmission (XRT) ore sorting. Magnet separation is able to reject about half of the feed mass with about 90% recovery of the rare earth elements (REE), and froth flotation can deliver a flotation concentrate amounting to less than 7% of the mass of ore and containing more than 50% of the REE values in the ore. Sulphuric acid baking allows recovery of about 90% of the Pr and Nd and more than 80% of the Tb and Dy. The acid bake plant will be coupled with a separation plant to recover the key magnet REE as separated and refined oxides.

Neo Rare Metals, a division of Neo Performance Materials Inc. (“Neo”) (TSX: NEO), is a global leader in the supply of gallium from recycled sources and operates the only commercial gallium production facility in North America, with over three decades of experience in the supply of high-purity gallium metal and related chemicals. Neo currently supplies approximately 5% of global demand for gallium, which is a critical enabler of high tech and clean energy applications such as light-emitting diode (LED) lighting, rare-earth permanent magnets, and wireless communications. Gallium’s strategic and technological significance is highlighted by its listing as a critical mineral or equivalent by Canada, the United States, European Union, Japan, the United Kingdom, South Korea, and Australia. Neo’s position as a market leader in gallium is built on a long history of excellence in extractive metallurgy, and includes important contributions made by the late Joe Ferron. This paper presents a technical overview of Neo’s gallium operations and experience in both primary gallium (recovery from alumina ore), and secondary gallium (recycling of gallium scrap), in addition to a current market perspective. Neo’s tenor as owner-operator of the former Ingal-Stade primary gallium facility and commercial producer of a Kelex impregnated ion exchange (IX) resin with applications in both gallium and germanium recovery are discussed. Neo’s commercial secondary gallium operations are based on a patented hydrometallurgical recycling process invented by Dr. Ferron. Key unit processes including leaching, solvent extraction, solution purification, and electro-chemistry, along with recent examples of process optimization are discussed.

NOVONIX developed a novel all-dry, zero-waste process to produce single-crystal nickel-based cathode active materials (e.g., NMC622, NMC811). The NOVONIX process, currently at the 10 tpa pilot-scale capacity, allows to synthesize phase-pure (layered NMC structures) and single-crystal primary particles with a good intraparticle elemental homogeneity. Furthermore, it has been identified that 1 Ah pouch battery cells incorporating NOVONIX’s NMC622 cathode powders have similar, if not superior, capacity retention (200+ cycles) than to battery cells containing commercial cathode powders with the same chemistry. As NOVONIX envisions the industrial development and production of SC-NMCs, it commissioned HATCH to help commercialize their process and compare it to the conventional processing route. The scoping study performed by HATCH indicated potential advantages of the NOVONIX process over the conventional processing route. The NOVONIX process avoids the generation of waste by-products such as Na2SO4 and potentially reduces operating (excluding material feedstock costs) and capital costs by 50% and 30%, respectively.

The Turnagain nickel project in northern British Columbia is emblematic of the likely next class of nickel producers. Low-grade ultramafic nickel projects such as Turnagain have many similarities with copper porphyry projects: massive deposits with high-throughput and low per unit cash flow, but their mineralogy can be challenging with numerous alteration minerals, variations in nickel deportment, and wide variations in nickel recovery. Project benefits can include significant by-product credits, and the ability to reduce greenhouse gas footprint through carbon mineralization in tailings—the most permanent carbon sequestration. The presentation will describe the Turnagain project and ore, and the mineral processing and geometallurgical programme undertaken to reduce technical risk.

The aim of this study was to explore the lithium carbonate precipitation from a lithium-ion battery leachate in a batch reactor by a gas–liquid and liquid–liquid reactive process, employing carbon dioxide and sodium carbonate, respectively. The effect of operating parameters including reaction time and initial reactant concentration was investigated. The obtained crystals were observed using scanning electron microscope, the crystal size distribution was studied by laser diffraction, and the crystal structures were analyzed by X-ray diffraction. Additionally, lithium content was evaluated by inductively coupled plasma spectroscopy. In the case of the liquid–liquid precipitation, scanning electron images showed that lower initial concentrations of lithium led to the formation of larger crystals, while higher concentrations yielded smaller particles with significant agglomeration. The results also indicated a higher yield for the liquid–liquid compared to gas–liquid precipitation, which could be attributed to the reaction parameters such as temperature and pH. The reduced solubility of CO2 in water at elevated temperatures, coupled with the pH decrease during the process, likely contributed to this disparity. Nevertheless, the use of carbon dioxide is of great interest since it is a greener and cost-effective approach in the lithium carbonate precipitation process. These experiments highlight the crucial role of the operating parameters in the lithium carbonate crystals.

For over 30 years, hydrometal has recycled nonferrous metals from complex secondary materials using hydrometallurgical processes. The tailor-made treatments developed by hydrometal contribute significantly to the development of sustainable solutions to the depletion of natural resources and fit naturally into the sustainable circular economy concept. Hydrometal’s expertise is based on a wide range of hydrometallurgical technologies that are unique in the world of the treatment of complex residues that are often considered as toxic and hazardous waste. One of these unique processes, developed recently and supported actively by Dr. Joe Ferron, is the recovery of germanium based on an innovative ion exchange process. After the leaching of complex secondary raw materials containing germanium such as zinc or iron by-products and copper cement from various industries, germanium is selectively recovered from complex solutions and concentrated 10- to 100-fold. This pure germanium concentrate can therefore be readily reintegrated into germanium refineries. This paper summarizes the methodology for developing such a process from proof-of-concept at lab scale to the evaluation of industrial performance at an industrial pilot scale.

The quality of a rare earth element (REE) concentrate can be negatively affected by the presence of fluorite. This study aims to better understand the high-intensity magnetic fluorite separation process from a finely ground REE concentrate to purify a REE-flotation concentrate. Using a flotation concentrate produced during mini-piloting, particle size and suspected agglomeration were first investigated using laser diffraction particle sizing. Laboratory-scale magnetic separation tests were carried out using a factorial design with magnetic induction intensity (10,000–20,000 Gauss) and the solids fraction of the pulp (10–20% w/w) as variables. The material tested comprised monazite and bastnaesite as REE-bearing minerals, as well as Fe-bearing dolomite, ankerite, apatite, and fluorite, the latter two being assumed to be diamagnetic. Results showed significant particle agglomeration in the concentrate before ultrasonication. Chemical and mineralogical analyses allowed for description of the recovery of the REE and gangue minerals in terms of their size, magnetic properties, and liberation. While magnetic separation was effective at rejecting fluorite, a significant portion was carried over to the magnetic fraction through association with paramagnetic ferroan dolomite and REE minerals. While a REE recovery to the magnetic product of 80% has been achieved, REE losses mainly resulted from difficulty in attracting fine (<5 μm) particles, even after multiple passes. Liberation may also hamper REE recovery which increased upon an HCl preleaching step. This study provides a better understanding of the impact of particle size and liberation on high-intensity magnetic separation of REE-bearing minerals from diamagnetic minerals.

Rare earth elements (REEs) are central to modern life’s technological advancements. Endowed with substantial mineral resources, Canada is a crucial potential source of these vital elements. This chapter addresses the development of beneficiation flowsheets for notable Canadian projects, each of which presents unique challenges due to low grades and complex mineralogies, necessitating innovative and cost-effective beneficiation techniques to render extraction economically feasible. Against the backdrop of the Critical Minerals Plan of Canada—an industrialization strategy that fosters a net-zero economy—this study highlights the national endeavor to secure a domestic source of critical minerals and spearhead sectors crucial for future sustainability, such as electric car battery production. In this study, we examined mineralogical characteristics and processing methods, including gravity separation, magnetic separation, and flotation, tailored to enhance REE recovery and grade. The investigation included detailed laboratory experiments assessing the impact of reagent choices, addition points, and pH on beneficiation outcomes. The study also delves into the environmental considerations surrounding the use of hydroxamic acid-based flotation reagent suites. This analysis aims to improve both the recovery rates and the quality of concentrates, enhancing the project’s economic and environmental sustainability. The findings highlight the imperative of further research to address existing knowledge gaps and embrace sustainable practices in the beneficiation of rare earth minerals, pivotal to the high-tech industry’s future and aligned with Canada’s strategic vision for a net-zero economy.

Solvometallurgy is an innovative approach to extract metals from primary and secondary resources. It relies on the use of eco-friendly and cost-effective nonaqueous solvents, such as deep eutectic solvents (DESs), to extract and recover metals of interest, while promising to minimize water consumption and the use of harsh acid/base chemicals in processing circuits. This work presents the outcome of a series of 24 h solvometallurgical leaching tests using waste printed circuit boards (PCBs) at a mild temperature of 65 °C. Four DESs were investigated, containing choline chloride (ChCl) as the hydrogen bond acceptor (HBA), ethylene glycol (EG), malonic acid (MA), acetic acid (AA), and levulinic acid (LA) as the hydrogen bond donors (HBDs), and iodine (I2). Among the DESs tested, ChCl:AA:I2 emerged as the most effective and selective solvent, extracting 94% of Cu, 78% of Ni, and 88% of Au, with 37% and 6% co-extraction of Fe and Al, respectively.

The Wicheeda rare earth carbonatite deposit has a measured mineral resource of 6.4 Mt averaging 2.86% total rare earth oxide (“TREO”) and an indicated mineral resource of 27.8 Mt averaging 1.84% TREO at a cutoff grade of 0.5% TREO. Mineralization comprises synchysite/parisite, bastnaesite, and monazite dominantly in a dolomite matrix. Beneficiation tests on multiple samples as well as a pilot plant have demonstrated 80% recovery into a mineral concentrate containing 50% TREO. Bench and pilot plant hydrometallurgical tests have shown a TREO recovery from concentrate to final product exceeding 90%. The proposed plant includes sulphuric acid baking, water leaching, and impurity removal by MgO precipitation followed by ion exchange for uranium removal. In an innovative approach for an acid bake solution, rare earths are precipitated with ammonium bicarbonate. The precipitate filtrate is treated with lime to precipitate Mg (as Mg(OH)2), Mn, and most of the SO4. NH3 is simultaneously volatilized and recycled internally. The barren filtrate from the above step is recycled to the water leach step. Sodium carbonate was considered as a possible rare earth precipitant. However, recycling of an Na-bearing filtrate to water leach was not possible because of double sulphate precipitation leading to reduced extractions. Testwork established that minor amounts of ammonium ions sent to water leaching do not cause double sulphate precipitation. The proposed beneficiation and hydrometallurgical plants have been designed at a pre-feasibility study level of detail, and capital and operating costs generated.

The most common method of cracking rare earth ores and concentrates is acid baking, in which concentrated sulphuric acid is mixed with the feed material, held at an elevated temperature to ensure sulphation of the rare earth elements (REEs), followed by water leaching the rare earths from the calcine. Impurity elements are often also sulphated, solubilized during water leaching, and typically removed from solution by hydrolysis augmented by ion exchange depending on the impurities. The result is a purified pregnant leach solution (PLS) typically containing 20 to 30 g/L total rare earth elements (TREE) with very low impurity levels. The solution can often be saturated in CaSO4 along with high Mg content (both leached from the ore/concentrate and from dissolution of the MgO or MgCO3 added to neutralize acidity and precipitate impurities) and with SO4 as the counter-ion. This purified solution must be processed to produce either a mixed REE precipitate or separated REE products for shipment to a downstream processing operation. The options for recovering REE from the purified PLS are discussed in this paper: important factors include the specification for the REE product, the desired overall water balance for the proposed operation, and reagent availability and costs.

The solvent extraction of rare earth elements (REEs) from their mixed solution in nitrate acid was performed. The experimental results showed that the extraction rates of La, Ce, Pr, Nd, and Y were 54.5%, 45.33%, 51.33%, 55.33%, and 89.77%, respectively, by the extractant, D2EHPA. Different operating parameters have been studied to get the optimum conditions, and the results showed that D2EHPA has a strong extraction ability for REEs, especially for yttrium.

In response to the global climate crisis, electrification of the transportation sector has been considered one of the best responses to target net zero emissions by 2050. This has prompted several car manufacturers (OEMs) to increase electric vehicle (EV) production, which puts a strain in lithium battery (LIB) material supply chains. In this context, LIB material recycling becomes critical. Recycling not only contributes to material supply but also releases four times lower carbon emissions vis-à-vis primary source metal extraction. Currently, two recycling processes are industrially used: hydrometallurgy and pyrometallurgy. These processing pathways have many challenges such as low recovery rates by pyrometallurgy and large waste generation by hydrometallurgy. Recently, a third recycling pathway has been proposed involving direct recycling of the cathode active material (CAM) like NMC cathodes (LiNixMnyCozO2). This nondestructive recycling approach allows for cathodes—not fully degraded—to be regenerated for reuse but also be upcycled into next-generation Ni-rich NMC cathode materials. In this work, the baseline of this pathway is demonstrated in a lab investigation with chemically delithiated cathodes. The process tested involved hydrothermal relithiation and calcination/annealing. Results will be presented as proof-of-concept demonstrating the direct recycling of NMC 111 and NMC 622 as well as the upcycling of NMC 111 to NMC 622 via co-addition of Li2CO3 and NiSO4.6H2O during calcination.

In Canada, spodumene (LiAlSi2O6) is the most common and widely explored among the lithium hard rocks. Its abundance and exploration potential have led to significant efforts in its study and development. It is noted that spodumene from Canada typically shows heterogeneous nature and simple mineralogy. The chemical components of spodumene pegmatites across different projects remain highly similar. The primary challenge in spodumene concentration lies in effectively separating it from sodic plagioclase (Na-feldspar) that shares similar crystal structure and has similar chemical composition with spodumene. This chapter presents lignosulphonate as depressant facilitating the separation of spodumene from Na-feldspar. The research employed surface chemistry, notably time-of-flight secondary ion mass spectrometry (ToF-SIMS) to explore the complexities of feldspar depression. The insights gleaned underscore potential challenges that may arise in industrial projects within Canada.

Current evaporation methods adopted in South America to extract lithium from brine are not suitable for Canadian brine sources in British Columbia, Alberta, and Saskatchewan. Not only is the process inefficient with significant losses, but cold climate conditions would require new processes or technologies. Much of the research and development focus is on adsorbent technologies with limited investigation on direct lithium extraction using solvent extraction due to poor efficiency when using conventional mixer-settlers as well as poor separation between monovalent and divalent cations with existing extractants. At the National Research Council Canada (NRCC), studies to identify new extractants to improve separation and the development of supported liquid membranes (SLM) to increase efficiency when processing brines are being undertaken. This chapter demonstrates the improved separation efficiency component of SLM. Benchscale monovalent separations were performed on a synthetic brine, 4000 ppm each of Li, Na, and K, based on the Mextral 3936H data sheet as a first benchmark. Results between shakeout solvent extraction, flatsheet SLM, and hollow-fibre SLM are compared with the manufacturer’s data sheet and against each technology.

The Mond Process involves, in the words of Lord Kelvin, “giving wings to nickel.” The process has been used for decades by a handful of companies around the world to produce more than 100,000 t of high-purity nickel and iron annually. The presentation will outline the merits and drawbacks of carbonyl processing of both sulfide and laterite nickel ores in terms of energy input and environmental footprint, plus the potential for producing new grades of battery precursors (such as high-purity nickel and iron powders) made by this unique, low-temperature vapor-phase method of nickel, iron, and cobalt deposition and particle formation.

The subset of rare earth elements, notably, neodymium, praseodymium, dysprosium, and terbium, are key ingredients used to make the world’s strongest type of magnets, the neodymium–iron–boron (NdFeB) magnet. Developed in 1984, these magnets now have broad applications and are found in a wide range of consumer and industrial products. After four decades of increasing use, little progress has been made in developing commercial-scale recycling of these magnets; however, considerable research has been made. This study explores the recycling of NdFeB magnets, focusing on the recovery of rare earth elements. Various methods, including mechanical separation, hydrometallurgical, and other processes, are examined for their effectiveness in recovering valuable materials in the context of real-world scrap. Environmental and economic implications are considered to assess the feasibility and sustainability of NdFeB magnet recycling, providing insights for a more circular approach to magnet production and consumption.

Addressing the threat of climate change requires a transition from fossil fuels to renewable energy sources like wind and solar for energy production. Though commercially viable and cost-effective, their intermittence necessitates efficient energy storage devices for on-demand use. Among energy storage technologies, rechargeable batteries, particularly lithium (Li)-ion batteries, are prominent due to their high energy and power density, compact size, and quick response. However, driven by soaring demand and geopolitics, Li-ion batteries face challenges such as high cost and potential shortages of lithium and cobalt. This underscores the need for innovative battery technologies using more abundant, safer, and cheaper materials than lithium. Post-Li-ion battery technologies are based on sodium, potassium, calcium, magnesium, zinc, and aluminum. A comparison between the cost, abundance, and gravimetric and volumetric capacities of these metals demonstrates that among them, aluminum is the cheapest, most abundant and delivers high capacity. This study examines three electrolytes (1-ethyl-3-methylimidazolium chloride, trimethylamine hydrochloride, and urea in combination with AlCl3), and three graphitic cathode materials (natural graphite, sonicated graphite, and graphene nanoplatelet) for aluminum battery development. Using cyclic voltammetry, electrochemical impedance spectroscopy, and rate capability tests, the study evaluates the electrochemical performance of these batteries to determine the most effective electrolyte and cathode material. The findings will be crucial for both industrial and academic researchers working on next-generation batteries that are more abundant, affordable, and high-performing. This research contributes to the ongoing effort to develop post-lithium-ion battery technologies, which are expected to play a significant role in the future energy storage market.

High-purity graphite demand for applications such as battery production is increasing rapidly. Different processes can be used to improve the purity of the graphite concentrate from the usual ~90% graphitic carbon grade (Cg) to the targeted 99.95% purity. While the caustic fusion route has the advantage of not requiring the use of HF or Cl2 and entails lower temperatures than thermal or thermo-chemical purification processes, it suffers from the need for significant quantities of NaOH. The recycling of NaOH in this application is thus strategic for economic and environmental reasons. Examples of NaOH recycling exist in alumina production, but its implementation for the purification of graphite poses other type of challenges because of the presence of different impurities. As the recycling of NaOH solution implies its concentration by evaporation of water after solution purification, questions thus arise about these aspects of the process and their economic implications. Using simulation and experimental results, this chapter examines the chemical feasibility of recycling NaOH for a caustic fusion purification of graphite and the economic aspects of the washing circuit. Results from the computer simulations of the washing step show that water management is critical for the economic viability of the process. Experimental results show that impurities (i.e., Al, Si) can be efficiently removed (50–75%) from the NaOH solution by the addition of Ca(OH)2, thus supporting the chemical feasibility of the process.

The escalating need for efficient electrical energy storage has intensified the pursuit of more advanced rechargeable batteries. Modern lithium-ion batteries (LIBs) have surpassed previous secondary batteries in both energy and current density. However, the performance of modern LIBs is constrained by their graphite anodes, whose theoretical maximum capacity has already been reached. To surpass this limit, a new anode material is needed, and transition metal sulfides are an excellent class of candidate materials, given their higher capacity, abundance, and good stability. This study investigates CoSx-CNT anodes in LIBs, where the material achieved an impressive 560 mAh g−1 initial charge capacity. However, as the cycling continued, the charge capacity of the cell increased, reaching 659 mAh g−1 after 90 cycles. The increase was attributed to increasing reversible reduction of the organic liquid on the growing solid electrolyte interface (SEI), which continued to reversibly store charge even as the conventional Li2S conversion reaction declined. This research demonstrated the potential beneficial effect of the growth of the SEI on the electrode’s reversible charge capacity, as opposed to previous studies in which SEI growth worsened cell performance. Insights from this system offer an improved means of studying the SEI’s properties and formation, as well as valuable knowledge for enhancing the cycle life and charge capacity of even non-TMS LIB anodes.

In this work, we review the leaching behaviour of rare earth elements (REEs) from ores with variable ionic character and highlight the influence of mineralogy on the processing strategy and terminal REE recovery levels. As the grades of ion-adsorption ores are low, the recovery of REEs must be maximized to justify the economic process, while ensuring minimum environmental impact. Differing from the traditional ionic clays that primarily exhibit physisorption, samples in this study contained around 30% clay material and had varying degrees of REE partitioning via physisorption and mineralization (in both acid soluble and refractory phases). This chapter presents insights gained by processing the clays by ion-exchange leaching (IXL) using various lixiviants and by acid leaching to identify the optimum REE recovery route. Some of the ores contained up to 60% of adsorbed REEs that could be easily recovered by IXL, while in some other cases, the REEs were mainly associated with mineral phases, thus requiring strong acid leaching. This research reveals the connection between the mineral makeup and REE leaching behaviour in a non-standard ionic clay samples and highlights the need to consider different processing routes to optimize REE recovery.

The only current industrial technology used in the world for rare earth (RE) separation is solvent extraction (SX) initially developed during the 1960s. After almost 30 years of inactivity in the field of RE processes and following the RE crisis in the 2010s work on RE separation has been reactivated in the Western world. Several teams began working on alternative technologies to solvent extraction in part because SX was considered as a Chinese technology. The promoters of these alternative technologies criticize SX for leading to high CAPEX and OPEX, having a high carbon footprint, and being inflexible. The combination between a large pallet of aqueous and organic chemistries and artificial intelligence allows to significantly decrease the OPEX and the environmental footprint of SX while improving its flexibility toward the variability of the RE feedstocks.

Cobalt is a critical material as designated by the United States Department of Energy. It is used in electric vehicles as a cathode material and in high-strength steels as an alloying addition. The United States currently relies nearly 100% on imports and secondary scrap materials for refined cobalt consumption. A flotation study was carried out to determine the viability of two-product flotation on cobalt and copper-bearing material from the Iron Creek deposit in Idaho. Rougher flotation testing was used to ascertain the most appropriate conditions for collector type and collector dosage. The as-received material had grades of 0.265% Co and 0.24% Cu. Out of several rougher flotation tests, a cobalt grade of 1.85% with a recovery of nearly 94.1% along with a copper grade of 1.37% with a recovery of 90% appears to be optimal. Differential flotation testing was undertaken to obtain separate copper and cobalt concentrates by depressing the copper bearing pyrite at a pH of 11.5. Cleaner flotation at a higher pH was attempted to further recovery of cobalt from the differential flotation copper concentrate. Regrinding to a particle size P80 of 80 μm aided in the recovery of cobalt to the cobalt concentrate. Locked cycle testing was also conducted to simulate an industrial flotation operation with results supporting the implementation of an industrial flotation circuit for the recovery of cobalt and copper as separate products.

Vale Base Metals operation in Long Harbour Newfoundland produces high-quality nickel, cobalt, and copper products that have direct applications in the global energy transition. Maintaining and increasing the output of these metals is crucial to meet the demand for this worldwide transition. The production of metals is based on the chloride-assisted pressure oxidation step, which is fully integrated into downstream unit processes where waste solids are separated from the process solution and impurities are removed. Operating the pressure oxidation step at high availability is important to the overall plant operation. Process equipment scaling on the discharge of the autoclaves has been an ongoing challenge. Steps to reduce scaling through several plant trials and an assessment of the mechanism of scaling have led to a possible solution to reduce the amount of downtime required to bring scaled process lines back online. In collaboration with Vale Base Metal’s technology group, a solution to further cool the autoclave discharge to <95 °C was tested and proven to be effective in reducing the incidence of scaling. This chapter will review the outcomes of plant trials and the successful implementation of a cooling methodology, with steps to provide a more effective engineered solution.

The Atlas Materials Process for nickel and cobalt recovery from saprolite ores has undergone extensive bench and pilot plant testing and is moving toward commercial implementation, with commissioning targeted for 2027. The process involves hydrochloric acid leaching of valuable metals, impurity removal to reject iron, aluminum, and chromium, production of mixed hydroxide precipitate (MHP) of nickel and cobalt, manganese removal, and magnesium product formation. The leaching and impurity removal residue may be used as a supplemental cementitious material (SCM) to replace fly ash in cement manufacture. Magnesium hydroxide may be precipitated by the addition of sodium hydroxide, and the resulting sodium chloride solution may be recycled through the chlor-alkali process to regenerate hydrochloric acid for leaching and sodium hydroxide for precipitation. The process is designed to produce no solid wastes and have a low carbon footprint through maximum use of renewable energy. The results of the bench and pilot plant testing will be presented and discussed.

The extraction and processing of rare earth elements (REEs) are of paramount importance due to their critical role in various high-tech and green energy applications. Geopolitical strains in the last decade have created significant volatility in the REE supply chain, with wide fluctuations in pricing and availability of the magnet REE. Commerce Resources, a junior mineral exploration company, is working toward the development of a REE mine (Ashram Deposit) and processing facility to offer an alternative to Chinese REE. This chapter presents an account of the development and optimization of the hydrometallurgical processing portion of the project. L3 evaluated both a hydrochloric acid and a sulfuric acid route. Following improvements in the flotation concentrate recovery and grade, L3 developed a streamlined sulfuric acid bake process for the extraction of REEs.

The horizontal single belt casting (HSBC) process has been developed in the last 26 years in Germany and North America, as an alternative to traditional casting processes, to produce thin strips (3–15 mm thick) of various steels, and light metal alloys. At the McGill Metals Processing Centre off-campus laboratory, the process has been applied at the pilot-scale, courtesy of MetSim Inc., to successfully produce aluminum and steel alloy sheets, 200–250 mm wide. These had good mechanical properties and good surface quality. In the present work, the computational fluid dynamics (CFD) software ANSYS-Fluent v. 19.0 was used to generate a 3D transient model, which was validated against experimental HSBC pilot-scale results for casting AA2024 and AA5182 thin alloy strips. The current CFD model researches the production of strips using a slightly modified liquid metal feeding system in terms of the “free fall distance” and the type of feeding system and their effects on the initial stages of the HSBC pilot process and the quality of cast products.

Transient liquid phase bonding (TLPB) is a joining process that can be implemented for a variety of material systems. It is of particular interest to the aerospace industry for both production and reparation of complex components which have strict requirements for mechanical properties and undergo high service temperatures. The use of TLPB has been successfully demonstrated and is used widely. Researchers have sought to develop models of the isothermal solidification (IS) kinetics, which are a critical component of TLPB, with some success in binary and simplified systems. To date, however, there has not been a robust analytical model which can estimate the TLPB process. Here, differential scanning calorimetry (DSC) is used to quantitatively study the IS kinetics of the Ti64-Cu system with a brazing temperature of 1050 °C (above the Ti64 ß-transus temperature of 980 °C). A half braze joint was subjected to a cyclical heat profile (1050–850 °C) where the liquid fraction of filler metal remaining was determined after each isothermal hold at the brazing temperature by measuring the enthalpy of transformation on each cooling segment. These measurements were subsequently used to estimate the required time at temperature to achieve complete isothermal solidification in a braze joint with a specified gap width. The predictions from the DSC results were validated using optical microscopy and SEM/EDS analysis. Successful full bond joints (FBJ) were produced using TLPB to examine the effects of varying foil thickness on the joint.

The production of aluminum alloys using the near net shape and cost-effective powder metallurgy (PM) route results in excellent microstructure and properties. This fact has led to extensive use of aluminum PM parts in the automotive and aerospace industries. In many cases, as-sintered parts may need further mechanical surface treatment to ensure the highest size precision. This can cause alterations in surface topography and wear behavior of aluminum. This study concentrates on the effect of sizing on the tribological properties of aluminum PM parts after applying sizing using different loads. Microhardness, wear resistance, and the coefficient of friction were measured and studied. Scanning electron microscopy (SEM) and confocal scanning laser microscopy were used to analyze the wear tracks. The results showed an increase in the wear rate in the sized samples. Also, sizing mechanical surface treatment resulted in enhancing the hardness in the aluminum PM parts.

The automotive industry faces the challenge of enhancing fuel efficiency while meeting global environmental regulations concerning emissions. Thus, advanced high-strength steels (AHSS) recently gained significant attention due to their improved combination of strength and ductility compared to conventional steels, allowing the manufacturing of lighter body-in-white assemblies. Among the AHSS, medium-manganese steels, which contain 3–12 wt% Mn and belong to the third-generation category, are of great interest. Since the mechanical and microstructural properties of medium-manganese steels rely heavily on the amount and stability of retained austenite, the impact of alloying with vanadium was explored. Two medium manganese steels containing 0 and 2 wt% vanadium were investigated. The results showed that the microstructure of the micro-alloyed medium-Mn steels consists of martensite and retained austenite phases. The findings also revealed that adding 2 wt% vanadium reduced the fraction of retained austenite coupled with the refinement of austenite grain size.

Surface integrity remains a significant concern in the additive manufacturing (AM) of titanium alloys, particularly due to implications for fatigue properties in critical applications, such as aerospace and biomedical. To address this concern, the current research investigates the effectiveness of ultrasonic pulsed waterjet (UPWJ) peening as a novel mechanical treatment for enhancing the surface characteristics of laser powder bed fusion (L-PBF) Ti–6Al–4V specimens. For UPWJ peening, a jet pressure of 69 MPa and a traverse speed of 800 mm/s were utilized, at a pulse frequency of 40 kHz. In addition to L-PBF, wrought Ti–6Al–4V specimens were also subjected to peening under identical UWPJ conditions, in order to assist meaningful comparisons. A comprehensive assessment of surface properties, including microstructure, surface roughness, residual stress, and scratch hardness, was conducted. The results indicated a significant reduction in the arithmetic mean height (Ra) for L-PBF components post-UPWJ peening, yielding a more consistent surface topography. Moreover, UPWJ peening induced substantial compressive residual stresses (approximately −800 MPa) uniformly across both AM and wrought samples. In terms of mechanical response, this treatment led to a notable 20% enhancement in scratch hardness (HSp). In conclusion, UPWJ peening showed the capability to offer improved surface properties and great magnitudes of compressive residual stress, positioning it as a feasible post-processing technique for enhancing the quality of PBF-LB fabricated Ti–6Al–4V components.

The presence of nonmetallic inclusions significantly affects the downstream processes of any liquid metal and compromises the quality of final products. Currently, inert gas injection is one of the processes for removing inclusions from liquid metals. The main target of inert gas injection is to form small bubbles that attach to the nonwetting surfaces of inclusions, facilitating their floatation to the surface of the molten bath. However, the efficacy of inclusion removal greatly depends on the sizes of gas bubbles generated within the liquid metal. Notably, small bubbles, forming at the orifice of gas injection nozzles, will normally coalesce into larger bubbles. Hence, a precise knowledge of their size and distribution within the liquid metal plays a very important role in maintaining optimum bubble size ranges. This range is ideally around 500 μm diameter, to also remove sub-50 μm diameter inclusions. This study introduces an in situ, real-time method for measuring bubble sizes and their distribution in liquid metals. It is primarily based on the liquid metal cleanliness analyzer (LiMCA) system. The LiMCA system was initially developed by Prof. Roderick Guthrie and Dr. Don Doutre at the McGill Metals Processing Centre (MMPC). LiMCA analyzers now serve as a tool for detecting inclusions in various liquid metals such as aluminum and steels. In the present study, a modified design of the LiMCA system was employed to investigate the sizes of the microbubbles formed. The successful detection and measurement of bubble size emphasizes the viability of LiMCA theory in effectively monitoring microbubbles in various liquid melts.

This work studied the effect of the T4 and T6 heat treatment on the tribological properties of as-cast A356.2 aluminum alloy under dry sliding reciprocating conditions. Samples were fabricated through a gravity die-cast process, followed by solutionizing at 510 °C and aging at 210 °C. The heat-treatment duration for each sample was optimized using data from micro-hardness, electrical conductivity, and microstructural analyses. Wear volume loss, wear rate, and coefficient of friction (CoF) of the A356.2 aluminum alloy were evaluated under a normal load of 5 N to identify the dominant wear mechanisms. The wear track’s worn surface and cross-section microstructure were examined using optical profilometry, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results indicated that the wear resistance of A356 alloy improved with T4 and subsequent T6 treatments. Delamination, adhesion, and oxidation were the predominant mechanisms during wear, followed by abrasive wear. The improvement in tribological properties is attributed to the increased ductility and hardness resulting from eutectic silicon phase refinement and the precipitation of Mg2Si.

In this study, B319 aluminum alloy matrix composites with varying amounts of graphene (0, 0.3, and 0.7 wt.%) were fabricated by a novel dispersion approach involving ball milling and spark plasma sintering followed by conventional gravity casting. The friction and wear response of the resultant castings were studied under reciprocating dry sliding conditions. The results suggest that the addition of graphene refined the microstructure of the B319 alloy, leading to improved hardness. Among the tested composites, the B319-0.3 wt.% graphene composite exhibited the best wear response, which was attributed to microstructural refinement, increased alloy hardness, and the formation of a graphene-rich tribolayer at the mating surfaces. The dominant wear mechanisms in the B319 alloy were (i) delamination, (ii) adhesion, and (iii) oxidation, followed by abrasive wear. However, the maginitude of these mechanisms reduced with 0.3 wt.% graphene addition, contributing to an overall improvement in the wear behavior of the B319 alloy.

Lightweight materials with superior mechanical properties have been a focal point of research and industry attention, especially in sectors like shipbuilding and aerospace. Microlattice is a type of metamaterial designed with precisely arranged patterns of struts. Additive manufacturing offers a great chance to create these complex structures. This study presents an analysis of the specific design of the BCC-Z structures by adding 1 and 3 plates which are made by maraging steel 300. The primary emphasis lies in examining the mechanical behavior during quasi-static testing, incorporating both experimental analysis and modeling, alongside the microstructural evaluations. To enhance comprehension of the microstructure characterization, an exploration of grain orientation, node’s porosity, and microhardness has been conducted. The mechanical properties improve significantly by adding plates to the primary BCC-Z structures.

This study investigates the fabrication process of a pure copper component using selective laser melting powder bed fusion (SLM) for industrial applications. Our investigation thoroughly analyzes the mechanical, thermal, and electrical properties exhibited by the additively manufactured (AM) sample. Notably, the AM sample demonstrates significant improvements in mechanical strength, showcasing higher ultimate tensile strength and elongation compared to conventionally manufactured counterparts. Furthermore, it meets or exceeds industry standards for both electrical and thermal conductivity, affirming its suitability for various industrial applications. Electron microscopy techniques elucidate the structural advantages conferred by the LPBF method, highlighting its potential for producing intricate and high-performance copper components. This comprehensive analysis not only underscores the feasibility but also emphasizes the potential superiority of SLM in fabricating lightweight and robust copper components for industrial usage.

This study investigates the impact of Si addition (0–0.5 wt%) on the strength and electrical conductivity (EC) of Al–Mg–Si conductor alloys, employing two distinct thermomechanical processing routes: the conventional route (CR) and the modified route (MR). A thorough microstructural analysis, utilizing techniques such as differential scanning calorimetry, transmission electron microscopy, and microhardness measurements, elucidates the combined effects of Si and the thermomechanical processing routes. The findings indicate that Si incorporation generally enhances strength at the expense of EC compared to the base alloy. Furthermore, adopting the MR yields superior strength and EC performance when compared to the CR.

This chapter investigates microstructural features in three dimensions. The study focuses on an additively manufactured (AM) nickel alloy with ultrafine grains as the base material. Sample preparation and characterization were performed using a dual-beam electron microscope equipped with focus ion beam milling (FIB). A specific area of the base material was selected, sectioned using the FIB column, and a micro-sized chunk box was extracted. This chunk box underwent a characterization cycle involving repetitive electron backscatter diffraction (EBSD) pattern detection and FIB milling. Subsequently, layer-by-layer EBSD data from the chunk box were assembled to construct a 3D representation of the microstructure. The layer-by-layer EBSD data of the chunk box was then assembled, resulting in a 3D representation of the microstructure that includes volumetric grain information. This innovative technique facilitates a more comprehensive study of additive manufacturing materials compared to conventional 2D methods.

The extensive utilization of the lightweight AlSi10Mg alloy in automotive and aerospace sectors stems from its high strength, favorable mechanical properties, and weldability, owing to its near eutectic composition of Al and Si. Age hardening is significantly influenced by Mg. This study examines AlSi10Mg alloy specimens produced at varying heights via laser powder bed fusion (LPBF), analyzing microstructure. Results reveal differences in melt pool size distribution and microstructural morphology at different heights, attributed to variations in cooling rate and gas entrapment during LPBF. Consequently, these microstructural variances will lead to diverse strengthening mechanisms and mechanical properties across specimen heights.

Nickel aluminum bronze (NAB) alloys play a critical role in maritime industries due to their outstanding combined properties such as high strength and corrosion resistance in seawater. In previous studies, researchers discovered that the functional properties of NAB samples produced via wire arc additive manufacturing are improved compared to the traditional methods. Hence, this research aims to investigate the influence of the selective laser melting (SLM) technique on the mechanical properties and corrosion performance of NAB specimens. NAB alloys typically contain a Cu-rich phase called α phase with a face-centered cubic (FCC) crystal structure and κ particles that are often categorized based on their chemical composition, physical characteristics, and distribution within the microstructure. In NAB alloys, the manufacturing process highly influences the microstructural characteristics. In the SLM process, the microstructure is refined due to the high cooling rate, therefore, an improvement in the functional properties of NAB specimens such as mechanical properties and corrosion resistance will be expected.

The study investigated the effect of a 0.3 wt.% Cu addition on the hot deformation behavior of an Al–Mg–Si conductor alloy and examined the influence of temperature on its performance. Hot compression tests were conducted at temperatures of 450 °C and 550 °C, with a constant strain rate of 0.1 s−1. Results from the tests at 450 °C revealed a 7.2% increase in peak flow stress compared to the base Al–Mg–Si alloy. Increasing the temperature to 550 °C resulted in a slight (<2%) peak stress increase for the alloy with 0.3 wt.% Cu. Microstructural analysis showed the formation of a significant amount of equilibrium precipitates after compression at 450 °C, while at 550 °C, these precipitates were mostly not present. Furthermore, samples deformed at 550 °C exhibited approximately 29 HV higher hardness after isothermal aging at 185 °C for 4 h, along with lower electrical conductivity compared to those deformed at 450 °C.

Hybrid additive manufacturing represents a novel approach in the industry, particularly for applications related to repair and maintenance. Discussion on the microstructural and physical attributes of hybrid bi-materials is centered around solidification and diffusion. Throughout the selective laser melting (SLM) process, the microstructure of the printed material experiences dynamic changes. The mechanical properties of the final product are intricately linked to the evolution of grain microstructure, a process heavily influenced by key parameters including scan velocity, laser power, and scan strategy, particularly at the interface. These parameters significantly affect the thermal history and the rate of temperature change during manufacturing. In this research, an advanced finite element (FE), multilayer model has been specifically tailored for AlSi10Mg alloy on cast Aluminum 2000 series within the SLM framework. The primary goal is to forecast thermal profiles and predict the geometric characteristics of the melt pool and the rates of solidification at the interface.

In comparison to other metal additive manufacturing technologies, electron beam melting offers several advantages, including higher energy efficiency, increased scanning speed, and reduced thermal distortion. The Ti6Al4V alloy is notable for its exceptional combination of strength, ductility, good high-temperature corrosion resistance, and a high strength–density ratio. Industries, particularly aerospace, where components endure low or elevated strain rates at service temperature, necessitate isothermal hot compression experiments on the homogenized alloy to understand its behavior. This research focuses on investigating the hot deformation behavior within the temperature range of 250–350 °C and the strain rate of 10 s−1. To predict the flow behavior of this microstructurally complex alloy, we employed the modified Johnson–Cook constitutive model and corresponding numerical simulation based on stress-strain and work-hardening characteristics. For the simulation of the hot deformation experiment, Lagrangian smoothed particle hydrodynamics in combination with the ABAQUS/Explicit subroutine was employed.

Additive manufacturing of light metal alloys has gained momentum lately in both academic and industrial domains. This necessitates a much deeper analysis of such materials under 3D printing processes to fully understand their behaviors corresponding to different sets of process parameters and predict the mechanical properties of the final fabricated items. Furthermore, the promising results accomplished by machine learning (ML) approaches in different fields of study are believed to guarantee reliability of these methods in forecasting the characteristics of the additively manufactured light metal alloys as well. In this paper, a comprehensive dataset regarding the melt pool morphology of stainless steels as the most common light metal alloys studied in the literature under the widely recognized selective laser melting process has been developed to train a wide variety of ML models. These models not only demonstrated exceptional performances in comparison with previous efforts and introduced new state-of-the-art melt pool geometry approximators but they also acknowledged the validity of the data set developed.

Most of the reactive metals may be separated by a high-temperature operation in their solid chloride salt form. The efficiencies of the separation depend on the vapour pressures of the corresponding salts with alkali chlorides. It may be beneficial to explore the possibility of performing the separation at lower temperatures in a mixture of two or more solid solutions and in a liquid salt formed by mixing two alkali chloride salts of the refractory metals. In this work, thermodynamic calculations using the Flood, Forland, Grjotheim (FFG) molten salt cycles are presented pertaining to the separation of refractory metals using solid or liquid mixtures of alkali chlorides.

An experimental study of the microstructure of a hybrid part, composed of two materials fabricated through the laser powder bed fusion (LPBF) process—specifically, AlSi10Mg on an Al-Cu cast alloy substrate—revealed variations in the microstructure of the first consolidated layer. These variations were found to contribute to a robust metallurgical bonding, subsequently enhancing the mechanical properties and overall performance of the LPBF-AlSi10Mg side of the hybrid part. In this study, we conduct numerical investigations to explore the microstructures of additively manufactured dilute Al–Si on the substrate Al–Cu alloy. A thermal model has been developed to systematically address the impact of laser processing conditions on the thermal behavior of the molten pool, partial melting of the cast substrate, and the dilution of its alloying elements during the LPBF process. To simulate the microstructure evolution of the candidate alloy, we employ a multi-component, multi-order parameter phase-field model. This model allows for a comprehensive exploration of the microstructural variations across the interface of the bimetal. Notably, the presented phase-field model can self-consistently simulate both heterogeneous and homogeneous nucleation events, providing insights into the triggers for morphological transitions. Moreover, it quantitatively explains the observed microstructural variation across the bimetal interface.

Titanium alloys combine outstanding mechanical properties with corrosion resistance and biocompatibility and are, therefore, used in many challenging applications. Nevertheless, especially in medical engineering, well-tailored properties such as a moderate Young’s modulus in combination with high strength and ductility are needed to ensure excellent osseointegration and minimize bacterial infections. For lightweight applications, on the other hand, a higher Young’s modulus, high strength, and sufficient ductility are needed. To fulfil the beforementioned requirements, the use of β-rich titanium alloys in combination with advanced thermo-mechanical production routes might be advisable. Weight reduction can be achieved by the application of additive manufacturing for which alloy development can be helpful to reduce anisotropy. In the present paper, related alloy and process design strategies performed at the Institute for Materials Science of the Technische Universität Braunschweig are discussed at four different examples, namely (1) the production of nano-structured Ti–13Nb–13Zr by equal channel angular swaging (ECAS) followed by recrystallization and ageing treatments to obtain a defined surface with a roughness close to 100 nm, (2) the application of martensite decomposition to increase the strength of Ti–6Al–2Sn–4Zr–6Mo, (3) the elaboration of a thermo-mechanical treatment procedure for Ti–36Nb–2Ta–3Zr–0.3O, and (4) the development of high-strength alloys based on CP-Titanium containing oxygen, iron, and molybdenum as major alloying elements for additive manufacturing.

AlSi10Mg, an aluminum alloy containing silicon and magnesium, offers a combination of lightweight, high strength, excellent thermal conductivity, corrosion resistance, machinability, and weldability, making it a valuable material in aerospace, marine, and various other industries. This study investigates the damage evolution and failure mechanisms of AlSi10Mg alloys fabricated through selective laser melting technology under quasi-static uniaxial tension. To replicate the tensile test, a finite element model is developed. By treating the damage parameters as design variables, the constants of the damage model are determined by minimizing the root mean square discrepancy between experimental and finite element model predicted responses. The Bonora damage model, based on continuum damage mechanics, is employed to estimate the damage evolution and material softening throughout the process. Additionally, the presence of defects not only alters the mechanical properties but also impacts the tensile behavior of the printed components.

The compromise between electrical conductivity and strength of aluminum alloys with additions of iron, nickel, and both iron + nickel was examined. As expected, pure aluminum showed the highest electrical conductivity of 61 %IACS with the lowest ultimate tensile strength (UTS) of ~54 MPa, while higher alloy content aluminum + iron and aluminum + nickel alloys showed electrical conductivities closer to 54–55 %IACS with corresponding UTS ranging from 66 to 117 MPa. However, the aluminum alloys with both iron + nickel had nearly the same electrical conductivity as the other alloys but tended to have higher UTS over 120 MPa. All the alloys examined had similar castability as assessed using a hot tearing susceptibility finger-type mold. Aluminum alloys with transition metal additions offer high electrical conductivity as well as high castability and strength over pure aluminum.

Titanium alloys, specifically Ti–6Al–4V, are widely used in the aerospace industry due to their exceptional high-temperature and strain fatigue properties, combined with a relatively low density. With the recent emergence of additive manufacturing technology, the aerospace industry is increasingly adopting this technique for fabricating Ti–6Al–4V parts, allowing for greater design freedom compared to conventional techniques. However, one of the challenges is determining its high strain rate and high-temperature properties, similar to the environment in which the parts are in service. Therefore, in this work, a compressive split-Hopkinson pressure bar (SHPB) technique equipped with an infrared radiation furnace was employed to dynamically test as-printed and heat-treated Ti–6Al–4V alloy samples, fabricated using the laser powder bed fusion (LPBF) process. The results of this work established the dependence of dynamic mechanical properties on the microstructural features of the Ti–6Al–4V alloy. Moreover, the dynamic response at elevated temperatures has been investigated, specifically at strain rates and temperature ranges of 200–2500 s−1 and 25–400 °C, respectively.

Metal paste deposition (MPD) is a new metallic additive manufacturing technique, which is closest in principles to the polymer-based fused deposition modeling (FDM) technique. The operational cost of MPD is lower than for the more typical laser-based metallic additive manufacturing techniques. Yet, its more recent apparition on the market means its feedstock catalogue is rather limited as of today. In this work, we studied the MPD printability of Ti–6Al–4V. This alloy is of particular interest for the additive manufacturing industry as it is the most widely used titanium alloy. Therefore, to decrease material costs, there is a drive to replace susbtractive approaches with additive approaches for this material. In this work, a paste was designed with adequate powder, solvent, and binder amounts so that it would flow and extrude with ease. As well, the paste was designed to avoid failure during sintering. Here are presented promising preliminary results regarding the density of Ti–6Al–4V parts printed by MPD.

Plasma electrolytic oxidation (PEO) emerges as a promising surface engineering technology for an array of light alloys, including aluminum, magnesium, and titanium. Its flexibility and growing importance in automotive, aerospace, biomedical, and many other industries highlight its versatility and potential. This electrochemical process uses electric discharges to create multi-component oxide coatings, giving materials outstanding physical, mechanical, and chemical properties. These properties include improved wear and corrosion resistance, biocompatibility, thermal stability, and beneficial dielectric characteristics. This presentation explores the properties of PEO coatings, with a focus on their strategic design through the customization of the PEO process to attain specific properties for different applications. The primary emphasis lies on enhancing corrosion and wear resistance, as well as biocompatibility.

This study involves an investigation into the microstructure and electrochemical properties of an additively manufactured Ti–6Al–4V sample fabricated through electron beam melting (EBM). The microstructural variances along both longitudinal and transverse planes with respect to the build direction were studied. The microstructure in planes parallel and perpendicular to the build direction was characterized using optical and scanning electron microscopy, X-ray diffraction, and transmission electron microscopy with energy-dispersive spectroscopy. Microstructural analysis revealed that different segments along the transverse axis were comprised of mainly α-phase with a minor β-phase presence. As the build progressed from the starting point to the end, both phases exhibited an increase in size, accompanied by noticeable segregation of vanadium and iron into the β-phase. Electrochemical behaviour was studied over time using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The film resistance of the commercially available wrought sample was marginally superior to that of the EBM samples. Notably, the film resistance of the EBM-transverse sample displayed a slightly more pronounced improvement with exposure time compared to its longitudinal counterpart.

This research has been focused on the intricacies of Ti-5553 alloy, a promising material for aerospace applications, employing the laser powder bed fusion (LPBF) process. The assessment of printability through the LPBF approach was carried out. The effects of volumetric energy density (VED) on the resulting microstructure and mechanical properties were investigated. An optimal VED was identified that results in a remarkable relative density, surface roughness, and uniform hardness distribution in as printed components. Moreover, the influence of α precipitate morphology on mechanical properties was a focal point of our investigations. By selecting extreme VEDs within an appropriate melting mode, comprehensive analyses using advanced electron microscopy, X-ray computed tomography, and mechanical tests were performed to evaluate the quality and microstructural development in the LPBF-made parts. The presence of intragranular nonlamellar α particles was identified as a key contributor to the balance between ductility and impact toughness. Furthermore, the conducted work introduced a novel approach—laser postexposure treatment during LPBF—to control microstructure formation, resulting in uniform and elongated grains, comparable with directionally solidified products used for enhanced creep resistance. Higher ultimate strength values were recorded for samples printed parallel to the building direction, primarily attributed to transgranular fracture. This finding offers valuable insights into the optimization of build orientations for enhanced mechanical performance. Additionally, the challenges posed by rapid heating and solidification rates through postprocessing heat treatment were addressed. Tailored in situ and ex situ heat treatment cycles were shown to effectively modify microstructure and enhance mechanical properties.

Currently, most of the natural graphite purification for battery anode material is achieved in China, using hydrofluoric acid leaching, which has been shunned in the Western countries due to safety and environmental concerns. This paper uses the available hydrofluoric acid (HF) safety guidelines and industry information to discuss the issues of transportation, storage, and utilization in a responsible manner. Health effects and environmental considerations are reviewed. Safe practices for handling the HF (both anhydrous and as aqueous) are considered. Proper selection of different materials of construction is discussed, for both the anhydrous and the aqueous HF.

Exploitation of mineral resources in steady primary ore deposits inevitably generates waste in large quantities. This waste sometimes occupies large areas and causes environmental risks but also offers economic opportunities. Mine waste can thus contain economical concentrations of chemical elements, in particular the so-called critical metals whose ever-increasing demand requires the search for new deposits. An example is the consolidated mining tailings from artisanal gold mining in the Bétaré-Oya gold district. Their mineralogical and geochemical studies reveal significant concentrations of Zr, V, Cu, Zn, Sr, Li, Cr, Co, Pb, Ag, and REEs distributed in primary silicate minerals, newly formed secondary minerals and accessory minerals. Consequently, well-regulated mining integrating the concepts of waste valorization and circular mining system could be more profitable industrially, economically, and environmentally.

Molybdenum, a critical component in alloys, stainless steels, and tool steels, has witnessed a consistent rise in demand primarily driven by its diverse applications. Beyond its traditional role in steel production, molybdenum’s versatile properties have found utility across various alloy systems and chemical compounds. Moreover, its integral role in sustainable energy technologies positions it as a linchpin in the global transition towards cleaner energy sources. As nations prioritize green infrastructure initiatives to spur economic growth, the demand for molybdenum is poised to escalate further. This paper examines the evolving landscape of molybdenum, analyzing global supply trends, its utilization across different industries, and the growing applications driving future demand. Additionally, it underscores the significance of effectively executing primary molybdenum projects to ensure a sustainable supply chain amidst increasing demand dynamics. This study reviews the molybdenum situation, including global supply, first and end use of molybdenum, and promising future applications.

In mineral processing operations of sulfide ores, the valuable nickel and copper-bearing minerals are concentrated, while the lower-value minerals such as pyrrhotite are rejected to the tailings. In recent years, nickeliferous tailings reprocessing has attracted significant attention due to the declining ore grades and an increased focus on the environmental threats posed by large tailings storage facilities. Thermo-concentration is a potential process for tailings treatment. Investigations since the 1970s have shown that thermo-concentration can recover nickel from the tailings while avoiding SO2 emissions. However, it is a highly endothermic process. Iron is added to the pyrrhotite tailings, and the mixture is thermally processed to produce an alloy phase assaying 10–20% nickel. In the present research, microwave radiation (2450 MHz) was utilized to thermo-concentrate nickel from the mixtures of nickeliferous pyrrhotite, iron oxides, and metallurgical coke. Microwaving of the reaction mixtures at 800 W was found to be sufficient to initiate the thermo-concentration process and form an alloy containing greater than 10% nickel.

Global forecasts suggest an increase in zinc production in the coming years. Along with cost, economics, and acceptance of zinc refinery products on the world market must be considered. The metals industry is facing several challenges, including a reduction in overall metal content and increased levels of impurities in the ore body and concentrate. Also, it is more important than ever to evaluate the sustainability and efficiency of the production process. The New Zinc Roaster is the result of continuous studies in the Frankfurt Research Center (historically Lurgi) and equipment development for numerous clients. Metso’s 50+ years of Fluid Bed Technology experience, coupled with a long list of international projects, has transformed the traditional roasting process. The integration of new equipment features combined with automation elements, additional sensors, and digital tools support today’s typical operation practices, to advance production targets through better control of operation and reduction of shutdown time. This article presents a short review of common practices in the industry, with a focus on how zinc concentrates high in impurities such as copper, lead, and silica are treated and how Metso is applying advanced process equipment in the fluid bed roasting process. An oven monitoring system is introduced as a method to reduce plant efficiency losses from fluid bed instabilities. The review concludes by discussing the integration of plant enhancements with modern digital tools, such as Metso’s digital solution suite for the roaster, gas cleaning, and acid plant. This approach aims to ensure increased plant safety and optimized operation, especially during upset plant conditions.

With the rising global demand for nickel, combined with the market shift towards battery production, the nickel resource landscape is evolving from the sulphide ores to the oxidic nickeliferous laterites. These laterite deposits contain two major ore types: limonitic and saprolitic. While nickel in the sulphide ores can be readily concentrated by flotation, this is not feasible for the oxide ores. Consequently, extracting the metal from the oxide ores involves treating large quantities of raw materials using numerous unit operations. Presently, the nickel in the saprolitic ores is extracted by pyrometallurgical processes, using carbon as the reducing agent. However, there is a need to develop more economical and environmentally friendly alternatives. One potential option involves the solid-state reduction of the nickel oxide in these ores using hydrogen-enriched natural gas, followed by the concentration of the resulting ferronickel. In this paper, a thermodynamic model was developed using HSC Chemistry® 7.1 to predict the equilibrium amounts of the products resulting from the solid-state reduction of a saprolitic ore using methane–hydrogen mixtures. Since nickel oxide has very high stability in the saprolitic ores, it was found that it was necessary to destabilize the nickel oxide using lime to facilitate reduction. Based on the modelling results, the optimum conditions were determined.

According to the latest reports, the iron and steel industry is not on course to achieve net-zero emissions by mid-century, as total emissions continue to increase. However, there is a growing number of announcements for new projects focused on near-zero emission iron and steel production. The hydrogen-based direct reduction has gained renewed interest among researchers, policymakers, and industries due to positive outlooks on sufficient and affordable green hydrogen production. The current study investigates the hydrogen reduction of industrial hematite iron ore pellets containing ∼96.9% Fe2O3. The isothermal reduction experiments were carried out using pure H2 in a custom-made thermogravimetric setup. The reduction experiments were performed at 700 and 1000 °C. The surface morphology, microstructure, and chemical composition were investigated for an intermediate state (50% reduced) and near-complete reduction (>95% reduced). The thermogravimetry results showed that, at 1000 °C, the average reduction rate during the initial stage (≤30% reduction) was 5.6 times higher than the reduction rate at 700 °C. Nevertheless, the increased reduction kinetics observed at elevated temperatures led to more microstructural defects, such as cracks and pores. Based on the macroscopic surface investigations, the severity of cracking seems to be strongly affected by the reduction temperature and, to a slightly lesser extent, by the degree of reduction at a particular temperature. Both temperatures exhibited a porous surface morphology; however, at 1000 °C, the progression of pore sintering over time resulted in a surface covered with dense iron particles.

Prior research has shown that microwave treatment diminishes the competency of kimberlites. However, there is a lack of information regarding the downstream processing of microwave-treated kimberlites. In this study, the microwave treatment of kimberlites at both the bench-scale and the pilot-scale was investigated. First, a comprehensive study of the kimberlite characteristics was conducted, including mineralogy, thermogravimetric analysis, and permittivities. Second, bench-scale microwave treatments were performed to investigate the heating behaviours of the kimberlites and their amenability to microwave treatment. Third, pilot-scale microwave studies were conducted to weaken the kimberlite by inducing microfractures along the grain boundaries. This weakened kimberlite requires less comminution energy, which could potentially lead to a reduction in diamond breakage and damage. Fourth, comparative comminution studies were performed on both the as-received (reference) and the pilot-scale microwave (PMW) treated samples, utilizing jaw and cone crushers followed by high-pressure grinding rolls (HPGR). These results demonstrated that the microwave-treated samples consumed less energy and generated fewer ultrafine particles (<38 μm) than the reference samples. Fifth, the coarse particles (>1 mm) were separated into both the concentrate (sinks) and the tails (floats) via dense media separation (DMS) with both fractions being subjected to liberation analysis. Sixth, the fine particles (<1 mm) were utilized in the settling studies. Finally, some conclusions and key findings are presented as well as recommendations for further research.

Biocarbons are promising alternatives to fossil reductants and have, for decades, been considered for metallurgy to allow for the reduction of CO2 emissions without changing today’s industrial processes and furnaces. The chemical, structural, and mechanical properties of biocarbon are different from those of fossil carbon. The approach to overcome this challenge is often to modify biocarbon or produce designed biocarbon with properties similar to those of coke or other fossil carbon sources. In this work, the approach has been to investigate how different properties of the carbon source such as reactivity, density, and onset temperature of the Boudouard reaction will affect furnace operation. A simulation tool for FeMn process, based on HSC Sim flowsheet which incorporated knowledge of mass and energy balance and kinetic data for Mn-ores, has been developed in earlier work. This HSC Sim simulation was further developed to incorporate knowledge about kinetic data for reactions involving carbon and to allow for distinct behaviour of the carbon from different sources. This gives the possibility to evaluate the effect of carbon properties on the Boudouard reaction, the energy consumption, and the CO2 emissions. Overall, the gas composition and the temperature distribution in different zones in the furnace will be altered. Mixtures of carbon sources are also considered, as well as the effect of potassium circulation in the furnace, known to accelerate the Boudouard reaction. The simulation results are discussed against current knowledge.

Hydrate-based desalination (HBD) is a cutting-edge, eco-friendly, and energy-efficient desalination method that can treat a wide range of saline solutions, including seawater, industrial effluents, and lithium-containing brines. The valorization of the latter via sustainable liquid mining, i.e., the concentration of dilute metal-containing aqueous solutions through clean water recovery, is of paramount importance to meet the skyrocketing demand for lithium in the years to come. This research focused on HBD’s potential of 0.1 M LiCl as a sustainable liquid mining technology for the water recovery and valorization of lithium resources with and without the presence of CO2 nanobubbles (NBs) as a kinetic promoter. Water recovery of 61.72 ± 2.15% and lithium enrichment factor of 1.87 ± 0.09 were achieved. Moreover, the water recovery was increased to 72.07 ± 4.18% and the enrichment factor reached 2.25 ± 0.14 in the presence of CO2 NBs after 180 min. Also, the desalination efficiency without and with CO2 NBs was 52.47 ± 2.33% and 50.12 ± 3.87%, respectively. Our experimental results indicate the viability of HBD in valorizing lithium resources by recovering clean water, thus offering valuable insights for sustainable water management in the lithium extraction industry.

In the present study, the thermodynamic properties of vanadium oxide in the CaO-Al2O3-VOx-SiO2 slag at 1873 K were investigated by equilibrating the slag with liquid Cu under C-CO equilibrium condition. The distribution ratios of V between the slag and liquid Cu were evaluated with respect to the slag composition. The distribution ratio showed a decreasing tendency with increasing Al2O3 concentration and an increasing tendency with increasing slag basicity.

The increase in metal mining, processing, and smelting activities has precipitated a substantial escalation in the contamination of soil by heavy metals. Ferrihydrite (FH) has been commonly used as an amendment for the immobilization of heavy metals in contaminated soil. However, FH suffers from drawbacks such as agglomeration and nonmigratory characteristics, which limit its practical application in soil remediation. Herein, a colloidal ferrihydrite material (FH-SG) was prepared by using organic molecules with multifunctional groups as well as negative charges and combined with ferrihydrite. The results showed that FH-SG with abundant surface hydroxyl groups (-OH) and large specific surface area (91.5 m2/g) can be well suspended, stable at pH 4–12, negatively charged at a wide pH (>4.8). When the FH-SG was added into contaminated soil with the rate of 1:2–1:4 g/mL, the stabilization rates of soil water-soluble As, Pb, and Cd reached 94.66–95.63%, 96.12–98.33%, and 95.52–96.37%, respectively, and the stabilization rates of soil bioavailable As, Pb, and Cd reached 72.22–77.19%, 49.39–52.91%, and 25.30–30.51%, respectively. The maximum migration distance in quartz sand and soil media with different particle sizes can reach 2.07–2.92 m and 0.78–1.08 m, respectively. Altogether, our findings clearly demonstrate that FH-SG exhibits better stabilization and migration than those of FH alone and most proposed FH colloidal systems. The FH-SG colloidal system holds significant promise for the remediation of various kinds of complex polluted soil.

Mining and processing of larger volumes of material per tonne of product will inevitably be required to deal with declining ore grades. This intensifies the current problems associated with water and energy supplies. A greater amount of fine wet tailings would also be produced and require management. Integrating pre-concentration into the process flowsheet has the potential to reject barren materials as early in the process and as coarse a particle size as possible. This, in turn, could reduce transportation needs, improve plant feed grades, and reduce environmental footprint which ultimately maximises resource and eco-efficiency. A number of pre-concentration technologies are available, and the best option is very case and ore specific. The integration of different technologies into a single pre-concentration flowsheet could potentially be an option. The process of identifying the best option is not always direct. Instead, the evaluation of options should start wide and considers ore suitability, technology capability, and economic viability. This paper includes case studies that apply the methodology developed by the authors over the years that evaluates the pre-concentration options including assessment of ore heterogeneity using geostatistics, mathematical process modelling, preliminary layouts, cost estimates, and financial implications for the overall operation (mine, pre-concentration, and downstream processing).

Water is a critical part of mines and processing plants, the management of which has environmental, social and financial implications. Water is closely linked to all activities on site, including residue storage methods. Tailings dams are the most common method of storing excess liquor and residue on site. However, tailings dam failures have resulted in loss of life and pollution of rivers and devastated the surrounding communities. In light of these catastrophic failures, projects are investigating alternative methods to store residue, such as filtered tailings stacking or repurposing the residue. Removing tailings dams means removing the almost “infinite” storage of residue and liquor. This chapter discusses the implications of removing tailings dams from a sitewide water and dissolved solids balance perspective. Due to the removal of the liquor storage associated with the tailings dams, buffer ponds need to be incorporated into the layout, along with a larger, more complex water treatment plant. These solutions increase both capital and operating cost of the site.

The global issues of climate change and the growing demand for critical metals required for the transition to clean energy call for innovative solutions in the field of mineral processing and metal extraction/recovery. To address this issue, we propose a carbon-negative mining technology focused on North American mine tailings containing silicate minerals. Our method uses renewable electricity to generate electrosynthesized hydrochloric acid (HCl) and sodium hydroxide (NaOH) from salt splitting. Acid (HCl or H2SO4) leaches metals from minerals, while NaOH is used to capture atmospheric CO2, which then reacts with leached elements to precipitate valuable products. This process results in the precipitation of metal carbonates ((Mn,Co,Ni,Cu)CO3 and (Mg,Fe)CO3), where the former is further refined for metal recovery and the latter sequesters CO2 as a stable carbon sink. The focus of the present work was to develop an efficient (low-energy) atmospheric leaching process (meaning more efficient than heap leaching and less energy intensive than high-pressure acid leaching (HPAL)) for a range of model silicate minerals (olivine, kimberlite, and serpentine) to evaluate the kinetics and extent of silicate dissolution and metal recovery and the properties of the residual minerals. The results obtained thus far can guide the design of an intensified process that takes advantage of early leaching kinetics and greater early filterability by utilizing alternating stages of extraction/depassivation.

Freeze concentration (FC) is a well-known technique for water separation by the formation of ice. Although primarily used in the food and chemical industry, the same principle can be applied to hydrometallurgical effluent treatments with the benefit of lower energy cost, lower carbon footprint, and less corrosion and scaling concerns than evaporative processes. However, commercial FC processes form ice as suspended solids which necessitates a complex purification system, making it uneconomical. In response, we have developed a continuous layer freeze concentration (LFC) device that grows ice as a solid rod that is then slowly extruded from the reactor, allowing simultaneous ice recovery. Freezing experiments conducted at various temperatures with a 1.5 molal MgCl2 solution all demonstrated at least 70% impurity reduction without any post-purification. Further increasing the impurity reduction to above 99% is achievable through deionized water washing and vacuum filtration but at the expense of a 60% loss in ice. A comparison with conventional suspension freeze concentration (SFC) showed our new LFC design to be superior at producing higher quality ice and reducing ice loss.

Recovery of metals from aqueous waste streams is a priority in making water recycling technologies economically viable. A solvent extraction (SX) raffinate from a printed circuit board recycling operation in northern Ontario with high concentrations of Na, Cl, S, and As was tested for water capture. This type of hydrometallurgical effluent is a challenge to commercial water recycling technologies like reverse osmosis, especially because of the high metal concentrations and the low pH of 1. To address this challenge, we are developing a hybrid forward osmosis and freeze concentration (FO-FC) process. Forward osmosis (FO) osmotically extracts water through a water-selective membrane into a concentrated draw solution (CDS): in this case, a MgCl2 solution. This concentrates the hydrometallurgical effluent and creates a diluted draw solution (DDS). Freeze concentration (FC) freezes the extracted water out of the DDS and regenerates the CDS while producing ice. Depending on the process water requirements and draw salt costs, further purification of the ice melt via reverse osmosis (RO) may be necessary, or it can be recycled as is. We operate with a commercially available FO membrane made by Aquaporin, which can tolerate lower pHs than other commercial options. This work presents a parametric study of the mass and energy balance requirements of the process using OLI flowsheet for the maximum water removable from the raffinate and the electrical energy required to do so.

A forward osmosis and freeze concentration combined with reverse osmosis (FO–FC–RO) process is being developed to recover water from hydrometallurgical effluents. The FO process purifies the contaminated water using a draw solution with higher osmotic pressure than the feed which allows water to permeate through a semi-permeable membrane from the feed to the draw solution. The concentrated draw solution is regenerated by the freeze concentration process, producing ice entrained with draw solute. After melting, an RO step is used to further purify the ice melt, obtain pure water, and increase the draw salt recovery. The RO operating pressure constrains the amount of water that can be removed from the hydrometallurgical feed through the process. This study investigates to what extent RO limits the FO-FC process. This work utilizes a simulation via the OLI Flowsheet software. A comparison between the simulation and experimental results proves that MgCl2 as a draw salt can be recovered in the RO step with 92.5% efficiency under 500 psi hydraulic pressure. Alternatively, when a Ce/LaCl3 mixed draw salt is used, it can be recovered with 93.5% efficiency under similar hydraulic pressure.

Lithium extraction from spodumene using the conventional method of leaching after sulfuric acid roasting produces an aluminisilicate residue stream containing gypsum. Outside of China where aluminosilicate residue can be sold as supplementary cementitious material, the residue is typically disposed of via tailings or dry stacking. A key issue in selecting alternative uses for aluminosilicate residue is its high gypsum content. This study discussed three flowsheets that eliminate or separate gypsum from aluminosilicate residue to improve its saleability. The first flowsheet is gypsum carbonation, which utilizes a basic environment where gypsum is reacted with carbon dioxide to generate calcium carbonate and a saleable by-product. The second flowsheet explores acidic filtration directly after water leach, followed by neutralization. The third flowsheet is calcination of the aluminosilicate residue to produce a strong coherent material that can replace backfill aggregate, thereby removing the need for a quarry and landfill.

The integrated management of smelter operations is founded on standard operating practices, including standardized operating modes. The system-wide conception of modes ensures that if new instructions are to be sent to one part of the smelter, e.g. the smelting furnace, then corresponding sets of instructions are sent to the other critical parts of the smelter, e.g. the offgas handling system. In general, a mode change is triggered when the risk-opportunity profile of the plant has deviated to the extent that a system-wide response is merited, passing a critical threshold. These theoretical notions had been initially been discussed in Automated Scheduling and Scientific Management of Copper Smelters (Navarra, Miner Process Ext Metall 125(1):39–44, 2016) but gained practicality through a collaboration with the Hernan Videla Lira (HVL) Smelter, described in System Dynamics and Discrete Event Simulation of Copper Smelters (Navarra et al., Min Metall Explor 34(2):96–106, 2017). The current paper now recounts the formative experiences surrounding the work at HVL, which led to data-driven framework that considered changing meteorological conditions within the Atacama region, quantifying the trade-off between the environmental risk of SO2 accumulation, and copper production. The same approach could be adapted to other metallurgical operations, to develop integrated responses to dynamically changing risk-opportunity profiles.

Conventionally, prosperity has been synonymous with financial success. However, a paradigm shift is underway, redefining prosperity. It challenges the conventional view of prosperity and envisages an economy where development harmonizes with environmental preservation as well as the health and well-being of local communities. Designing Sustainable Prosperity (DSP) is an approach to solve complex problems which embeds the United Nations Sustainable Development Goals (UN SDGs) into decision-making. DSP redefines prosperity to allow for comprehensive measurement and consideration of the extractive industry’s impact on water, air, land sustainability, and people. One of the distinctive features of DSP is the innovative use of the UN SDGs and their indicators to prioritize business cases. DSP is a whole systems solution designed for specific regions, equipping them with resilience to face an uncertain future. DSP transcends financial performance by contributing to local communities’ benefits, global health and well-being, and protecting the environment.

Due to climate change, we are facing challenges to decarbonise and increase resource utilisation in critical metals. This requires more efficient processing, at higher throughputs and with reduced waste. Nickel is facing increasing demand due to the increase in demand for batteries in the push towards electrification. The existing hydrometallurgical technologies commonly used for nickel laterite ore leaching include HPAL (high pressurised acid leach), the Caron process, atmospheric sulfuric acid leach and heap leach. These technologies all have their disadvantages which make it difficult for them to meet the demands of the future with the current challenges that we are faced with. It is important when considering alternative processing methods that they meet the current climate change challenges by achieving a higher resource utilisation while moving towards the ultimate goal of zero waste. This chapter aims to showcase a number of new alternative leaching processes including nitric acid leaching, step temperature acid leaching (STAL) and hydrochloric acid leaching. The most important aspects of these new leaching processes are presented and compared with the existing nickel leaching technologies. These demonstrate through innovation a reduced waste future is here and a zero waste future may be possible.

A big share of ferro nickel for the stainless steel industry is coming from nickel pig iron (NPI). There is no environmental data on the different production routes of NPI in the public domain. This chapter will show how environmental impact (here global warming potential [GWP]) can be calculated using basic technical data for processes like rotary kiln, electric arc furnaces, or blast furnaces. These basic data are modelled in the thermodynamic modelling software HSC 9.1 where pyrometallurgical processes can be simulated. The resulting consumption data for the different processes are then transferred to the life cycle assessment (LCA) for Expert Software from Sphera where the GWP is calculated.