New Directions in Mineral Processing, Extractive Metallurgy, Recycling and Waste Minimization

Considering the two most important issues the ironmaking industry faces today, i.e. energy consumptionEnergy consumption and greenhouse gas emissions, it would be advantageous to utilize the concentrateConcentrate-size raw materials directly without pelletizing or sinteringSintering, especially without the use of coke. This plenary lecture describes two such processes developed at the University of Utah. One is the Flash Ironmaking Technology (FIT),Flash Ironmaking Technology (FIT) and the other is a moving-bed process for continuous ironmaking with gaseous reduction of iron ore concentrateConcentrate (MBIT). These technologies are designed to produce iron directly from iron concentrateConcentrate without requiring pelletization/sinteringSintering and cokemaking. They take advantage of the high reactivity of the concentrateConcentrate particles and will significantly reduce energy consumptionEnergy consumption and carbon dioxideCarbon dioxide emissions compared with the current processes. The process of the development from the conception of the idea, to kinetic feasibility establishment, and to the operation of a prototype facility will be discussed.

PhosphorusPhosphorus is an important element for both the agricultural and industrial sectors, especially within semiconductor and pharmaceutical industries. However, the resource of phosphorusPhosphorus, and high grade phosphatePhosphate rock deposits are rapidly being depleted and finding phosphorus secondary resources turns to be more and more crucial. Steelmaking slagSteelmaking slag is considered an attractive phosphorusPhosphorus secondary resource as it contains relatively high phosphorusPhosphorus content and has a constant supply, relatively fixed composition with minor contamination. The present study used graphite powder as a reducing agent to reduce FeO-CaO-SiO2-P2O5 synthesized slag into phosphorusPhosphorus. And in this study, it was clarified that phosphorusPhosphorus could be evaporated from steelmaking slagSteelmaking slag by carbothermic reductionCarbothermic reduction at 1573 K. During the carbothermic reductionCarbothermic reduction process of synthesized slag, phosphorusPhosphorus was detected to be distributed into gas phase, metal phase, and part of it kept in residual slag phase. And partial phosphorusPhosphorus transferred into the gas phase could be recovered.

There has been a decrease in the grade of copperCopper concentrateConcentrate, leading to an increase in impurities load of copper smelterCopper smelter globally. Among such impurities, leadLead has a detrimental impact on electrorefining operation causing the passivation of the anode. Although reductive smelting of dust to produce leadLead bullion has been known to be an option of leadLead bleeding off the copperCopper production circuit, impurities other than leadLead included in “dirty concentrateConcentrate” in recent years may suffer the operations of leadLead smelting and successive refining of the bullion, as well. The present paper will suggest a process from pretreatment of feed to the leadLead smelter to pyro-refining of bullion to ensure satisfactory quality of bullion while managing impurities other than leadLead and discuss process factors that are crucial for the process design of the present process.

Copper smeltingCopper smelting furnaces are typically lined with magnesia-chromite refractories. This paper evaluates the common refractory wear mechanisms of infiltration, spalling, and chemical attack as observed in the copper anode furnaceCopper anode furnace. All these wear parameters leadLead to severe degeneration of the brick microstructure and to a decreased lining life. Additionally, the influence of infiltration on the thermal conductivity and temperature field on a simplified furnace lining was investigated by means of numerical simulationNumerical simulation. A steady state heat transfer finite element analysisFinite element analysis was conducted using a theoretical model of a cross-section of the furnace. Two cases with different material properties were considered. The first case considered virgin lining and the second a lining with deep slag infiltrations. Accordingly, a detailed investigation and understanding of the wear mechanisms through “post-mortem studies” in conjunction with numerical simulationsNumerical simulation is an important prerequisite for the refractory producer.

The pre-reduction reactions of high Mn-oxides in Comilog and Nchwaning manganese ores have long been investigated because of their potential to reduce both the specific energy and coke consumptions of FeMn alloys. However, the performances of most industrial furnaces do not beneficiate from fully completed pre-reduction reactions. In this context, a new incremental approach, using an experimental and numerical tool, is developed to investigate the mechanisms involved from the microscale to the industrial scale using experimental toolsExperimental tool from the laboratory set-ups to pilot equipment. The pre-reduction optimization study was started at the microscale. Results of the lab-scale trials on both ores at different temperatures, CO/CO2 ratios, and the numerical model simulating the kinetics and heat transfer of the pre-reduction reactions will be presented. The main kinetic parameters have been identified from the lab-scale trials using the numerical model, compared to the literature, and interpreted to explain the physico-chemical behavior of pre-reduction.

Rare-earth-elements (REE)Rare-earth-elements (REE) can be used as alloying agents to improve the properties of aluminumAluminum alloys. REE are often added in the metallic form to produce the alloys, but the high cost of REE metals makes the alloys expensive thus limiting their application. An alternative way to make REE-Al alloys is by reacting REERare-earth-elements (REE) oxides with light metals. For this route, secondary light-metal resources, such as aluminumAluminum drossDross, have the potential to be used to reduce the cost of alloy production and at the same time limit waste generation. In this study, a systematic thermodynamic evaluation of aluminum-lanthanumLanthanum (Al-La) alloy production using lanthanum oxide (La2O3) and different light-metal secondary resources was carried out. Three different Al dross compositions were evaluated, each with different metal/metal oxide ratios. Based on the analysis, Al drossDross can successfully be used as the starting material for this process. The La2O3 (10 wt% of total charge) was completely reduced in all simulated compositions. Additional calculations were carried out to simulate a process in a Rotary Salt Furnace (RSF). From this analysis, the use of chloride salts is predicted to only slightly reduce the yield, but the use of fluoride salts should be avoided.

In different nonferrous metal producing industry sectors, the impurity element iron has to be removed from the process solution. Examples are the jarositeJarosite or goethiteGoethite from nickelNickel or zincZinc production but also the red mud from aluminum production. Regardless of environmental concerns, the material is land filled in almost any case, although valuables such as indiumIndium, silverSilver, gold, nickelNickel, or zinc are present in considerable amounts. Within the presented research, a low carbon dioxide emitting multi-metal recovery from such iron containing residues by means of a selective chlorinationSelective chlorination extraction has been fundamentally evaluated by experiments but also by comprehensive thermodynamic calculations. The paper summarizes the thermodynamic fundamental concept exploited to separate the dominating iron matrix from the valuable elements and shows verification experiments in a lab size of several grams.

The current interest in space-based mineral and metal extraction technologies, and the increased likelihood of establishing research facilities on the lunar surface, provides a strong impetus for high vacuum metallurgical research. The current work examines the viability of a thermal dissociationThermal dissociation process for metal and metal oxide extraction from beneficiated and un-beneficiated lunar feedstocks. Thermal dissociationThermal dissociation experiments using lunar regolith simulants and pure oxide samples were performed using a bespoke apparatus involving a vacuum reactor coupled with a solar simulator heat source. Specific focus was given to sub-liquidus operation and the sublimation of metal oxides under low temperature and low vacuum conditions. The thermodynamic and kinetic considerations, as well as the practical demonstration of such a process, are also discussed. This work demonstrates the potential of utilising the natural high vacuum conditions on the Moon for developing novel high vacuum extraction processes.

In the flash furnaceFlash furnace for copper smeltingCopper smelting, Cu loss in the slag is an economically important topic. It is known that the size of the matteMatte droplets, one of the significant factors of mechanically entrained Cu loss, is complicated by the local number density in the reaction shaft, initial size, and chemical composition of the concentrateConcentrate. Numerical simulationNumerical simulation based on a dynamic model can clarify the various factors’ effects instead of the experimental measurements restricted in the industrial high-temperature reaction field. In this study, the collisionCollision and coalescenceCoalescence behavior of many droplets consisting of matteMatte and slag with various sizes assumed in the flash smelting reaction shaft is calculated explicitly by smoothed particle hydrodynamics method considering interfacial deformation. This numerical simulationNumerical simulation visualizes droplets' interfacial deformation, matteMatte coalescenceCoalescence, and slag interference. It reveals the considerable effect of interfacial energy among matteMatte-slag-gas on each droplet size growth.

To design, develop, and efficiently operate the new technologies needed by the metallurgical industry,Industry we need a skilled workforce with a sound understanding of the key aspects of the value chain and the metal processing cycle. That is, we need a workforce with specialist expertise in metallurgical engineeringMetallurgical engineering with the ability to use advanced computer-based tools to analyse, predict, and control these processes. With few exceptions, the availability of, and enrolments in, metallurgical engineering educationEducation programs around the world are low, and programs are under-resourced. There are major issues in relation to attracting students, designing and delivering programs, and ensuring financial sustainabilitySustainability of our universityUniversities programs. In this context, we explore the approach taken to the development of the metallurgical engineeringMetallurgical engineering program at The University of Queensland, and the teaching of undergraduate students and engineers working in the metallurgical industryIndustry. These examples illustrate the importance of engagement with, and support from, industry in order to significantly increase the number of metallurgical engineeringMetallurgical engineering graduates and sustain metallurgical engineering as a discipline in our universities.

The hydrometallurgical separation of cobaltCobalt and nickelNickel was achieved from HCl leached solution of spent Li-ion batteriesLi-ion batteries, while applying Cyphos IL104 as a potential extractant. CobaltCobalt extraction significantly increases with increasing Cyphos IL104 and Cl− ion concentrations, and equilibrium pH (pHeq). Under the optimized condition of 0.8 mol·L−1 Cyphos IL104, 3.0 mol·L−1 Cl− ions, pHeq value 5.0, and O/A ratio of 2/3 could extract >99% Co with only 3% Ni into the organic phase. The back-extraction of cobaltCobalt performed with 2.0 mol·L−1 H2SO4 solution yielded 99.95% stripping efficiency and was crystallized to obtain high-pure CoSO4.xH2O crystals.

SeleniumSelenium and telluriumTellurium are semiconductors. TelluriumTellurium forms inorganic and organic compounds that are superficially similar to corresponding seleniumSelenium compounds yet dissimilar in terms of properties and behavior. The first part of this paper describes seleniumSelenium and telluriumTellurium in terms of their chemical reactions. The second part presents applications of seleniumSelenium and telluriumTellurium recovery processesRecovery process that are hot topics in today’s extractive metallurgy field.

HydrometallurgyHydrometallurgy is a widely applied technology to extract valuable metals from spent lithium-ion batteries. H2SO4-H2O2 combination is the most common lixiviant used for leachingLeaching black mass. However, the use of H2O2 poses several problems including instability and high reactivity in high temperature leachingLeaching. In here, nickel matteNickel matte (NM; Ni-Cu SulfideSulfide) is proposed as a novel reductant in H2SO4 leachingLeaching. The effects of NM dosage, pulp density, H2SO4 concentration, temperature, and reaction time on metal recovery have been studied. The results demonstrate that NM improves metal dissolution. With leachingLeaching condition H2SO4 1 M, pulp density 5%, and temperature 70 °C, both Co and Mn recovery are doubled when NM is added. A significant finding was that the effect of temperature on leachingLeaching efficiency was insignificant. High leachingLeaching efficiency was attained at high pulp density (210 g/L), low leaching temperature (10 °C), and short period of time (30 min). The recovery of Li, Ni, Mn, and Co in this leachingLeaching condition was 93%, 50%, 69%, and 88%, respectively. Aside from its advantage as reductant, NM addition could increase Ni concentration in leachate, which may further facilitate direct nickelNickel-rich cathode syntheses using precipitation and crystallizationCrystallization.

Renewed interest in green hydrogen energyHydrogen energy due to its versatility and ability to decarbonise numerous economic sectors prompted research on the evaluation of sustainabilitySustainability of associated technologies. Proton Exchange Membrane (PEM) water electrolysis is a promising technology to produce hydrogenHydrogen gas from water electrolysis using renewableRenewable power. However, PEM electrolysersPEM electrolyser use rare noble metals and other expensive materials. Furthermore, the availability and supply risks are additional concerns for the critical metals. Hence, this paper explores the review of the recyclingRecycling process of end-of-life PEM electrolysersPEM electrolyser from the point of collection to the final material recovery and the potential reuse in the manufacturingManufacturing process. Several studies have highlighted existing and novel recyclingRecycling technologies for the different materials used in electrolyser components. Some of these methods include hydrometallurgyHydrometallurgy, pyrometallurgy, transient electrochemical dissolution, selective electrochemical dissolution, and acidic process. Overview of these processes and implication of recyclingRecycling are presented here.

The electrodepositionElectrodeposition of critical base metalsBase Metal and rare earthRare earth metals using a eutectic mixture of urea and choline chlorideCholine Chloride (IL) was discussed. The maximum current efficiencies obtained for Co, Zn, Pb, and Cu were 95%, 91.3%, 96.4%, and 97%. The deposition of alloys of zinc like Zn-Sn, Zn-Cu, Zn-Ni, and Zn-Mn and alloys of nickelNickel like Ni-Mn, and Fe-Co–Ni was reported. The co-deposition of rare earthRare earth elements like Co-Nd and Sm-Co alloy was also carried out, because rare earthRare earth metals cannot be deposited alone in urea melt due to their high negative reduction potentials of the rare earthRare earth ions. The effect of Urea and choline chlorideCholine Chloride or EMIC or BMIC on the electrodepositionElectrodeposition of critical base metalsBase Metal and rare earthRare earth elements was discussed. The critical parameters in the electrodepositionElectrodeposition processes were identified, such as current density and efficiency in metal and alloy production.

This study analyzes open access data on the input and generation of end-of-life lithium-ion batteryLithium-ion battery waste supply for a potential commercial battery recyclingBattery recycling industry in BangladeshBangladesh.. Four main sources were identified in the battery waste pool: mobile phones, laptop and tablet PCs, small handheld devices, and hybrid electric vehicles. Their predicted generation rate and volume by type were forecasted to the year 2041 based on the available historic data and assumptions. Such batteries contain commercially recoverable quantity of base metals like Co, Ni, and Mn as well as other common metals like Li, Cu, Al, and Fe. These metals are in high demand for Bangladesh where urban mining and ‘informal recyclingRecycling’ currently present challenges to public health, ecological safety, and resource efficiency. A precise estimate of secondary resource inventory, cumulative growth, and economic forecasting of battery waste can pave the way for ‘formal recyclingRecycling’ which will attract national and international investments.

For a smooth transition to a CO2-neutral society, spent lithium-ion batteries (LIBs)Spent lithium-ion batteries must be recycled. Swerim has made significant advances in this field. This paper will summarize the major projects and highlight their major results. In the pyrometallurgical study, an optimized pyrometallurgical recyclingRecycling process was developed and demonstrated in a pilot electric arc furnace (8-tonne scale). The developed process demonstrated a high recovery of cobalt and nickel of >98%, and most of the lithium was recovered into a Li-rich dust fraction which could be upgraded into lithium carbonate by carbonated water leaching. In the shredding and thermal treatment study, a homemade simulatorSimulator was constructed to simulate the combined mechanical and thermal treatment of spent LIBs cells. Studies were conducted to examine the possibility of recovering electrolyte components as well as to understand the mechanisms behind the formation of gases generated during shreddingShredding.

Understanding the fundamental knowledge of leadLead reduction from lead-bearing materials using hydrogenHydrogen is essential for developing a carbon neutral leadLead production process. RecyclingRecycling of leadLead from secondary resourcesSecondary resource using hydrogenHydrogen as a reducing agent is industrially important to promote circular economy, resource efficiency, and reduction of carbon footprint. The current study evaluates and compares the general reduction mechanismReduction mechanism of PbOPbO with a more complex lead-containing compound, PbO-SiO2 glass/slagSlag. Isothermal reductions were carried out on pelletized PbOPbO and PbO-SiO2 (70wt% PbOPbO and 30wt% SiO2) using hydrogenHydrogen at 350 to 800 °C (for PbOPbO) and 300 to 700 °C (for PbO-SiO2). The results from microstructural observation showed that uniform, globular, non-wetting leadLead droplets formed on the surface of PbOPbO pellets. The leadLead droplets covered the whole surface, which appeared to inhibit further reduction. In the case of PbOPbO-SiO2, the viscous nature of the glass/slagSlag appeared to significantly hinder diffusion of hydrogenHydrogen within the pellet, resulting in a low reduction rate.

TitaniumTitanium alloy grinding scrapsGrinding scrap (TAGS) have a production of 30 thousand tons annually. They contain large titaniumTitanium resources as by-product from the titaniumTitanium alloy machining process. TAGS cannot be sent back directly to the vacuum smelting process due to its high-content of impurities such as the grinding wheel ash and titaniumTitanium oxides. In this study, a process of Electrostatic SeparationElectrostatic separation-Oxidative RoastingRoasting-Acid LeachingLeaching was applied to separate and recover titaniumTitanium from TAGS. The results indicate that 76.61% titaniumTitanium could be recovered during electrostatic separationElectrostatic separation process under the optimal conditions. The final product of TAGS containing 91.44% titaniumTitanium dioxide was obtained after optimized physical separation, oxidative roastingRoasting followed by hydrochloric acid leachingLeaching process. The product meets the requirements for feed raw materials required to prepare the industrial titaniumTitanium dioxide. It was found that aluminum was the major impurity in the titaniumTitanium-based product in the form of corundum.

Rwanda has not experienced any mine closureMine closure since mining operations started in the 1930s. To date, there is no information on good practice mine closureMine closure procedures despite the presence of old mining operations. Therefore, this study is the first of its kind to scrutinise the closure planPlan for Rutongo, a tinTin mine that has existed for over 80 years and is approaching its mine life. The study seeks to quantify heavy metalHeavy metals levels in mine wastesMine wastes and suggests a closure planPlan for waste rockWaste rocks dumps (WRDs) and tailingsTailings storage facility (TSF) so as to reduce contamination effects during and after cessation of operations. Geochemical characterization using X-Ray Fluorescence (XRF) and Inductive-Coupled Plasma Mass Spectroscopy (ICP-MS) was conducted. Results indicated the presence of pyrite and arsenopyrite, the deleterious elemental concentration ranging from 120 mg/kg to 710 mg/kg As, 10.32 mg/kg to 22.35 mg/kg Co, and 8.6 mg/kg to 128 mg/kg Cr. When these results are benchmarked against various soil quality standards, it is evident that the mine wastesMine wastes are contaminated by As and a critical concentration of Cr and Co. A mine closureMine closure planPlan with remediation and containment strategies for bio-accumulation of As, Cr, and Co and use of covers that have a capillary barrier to minimise water percolation, and a top soil that supports vegetation backed by hyper-accumulators was recommended.

Copper smeltingCopper smelting slagSlag from Luanshya of the Copperbelt province of ZambiaZambia with about 2 weight% copperCopper, 0.2 weight % cobaltCobalt, 0.8 weight % chromiumChromium, 6 weight% sulphurSulphur, and 18 weight% ironIron, the remainder being silica, aluminium, calcium, and magnesium oxides, was processed. SulphurSulphur is mostly present in elemental form. The presence of sulphurSulphur and chromiumChromium makes this slagSlag an environmental hazardHazard. Mineralogical examination showed that chromiumChromium and cobaltCobalt are predominantly present in chromite and complex fayalite phases, respectively. However, copperCopper is mainly present in the sulphide or matteMatte form. CopperCopper was upgraded to more than 25 weight % via a combination of screening, magnetic separationMagnetic separation, and froth flotation. SulphurSulphur was recovered as a concentrateConcentrate at a grade of 73 weight % via pre-flotation. Reductive roastingRoasting followed by magnetic separationMagnetic separation or acidic leachingLeaching was carried out. ChromiumChromium was upgraded by a factor of 8 in the weakly magnetic fraction. Recovery of 55–70% for cobaltCobalt was obtained after acidic leachingLeaching of reductively roasted samples.

The worldwide ever-increasing vehicle uptake escalates the number of end-of-life lithium-ion batteries that need to be managed. Aluminothermic reductionAluminothermic reduction is considered as an alternative approach for separating Li and Co from LiCoO2, the most common material used as batteries’ cathode. The current study evaluates the potential use of three different aluminum sources (chemical grade, waste swarf, and waste drossDross) as reductants for the aluminothermic reductionAluminothermic reduction process. Systematic thermodynamic analyses have been carried out using the FactSage thermochemical package to identify the optimum conditions and the reaction products at various temperatures. Selected experiments were carried out to demonstrate the process. In the case of reduction with chemical grade aluminum, Co could be extracted as Co metal or Co–Al alloy while Li is distributed to Li(g) and slagSlag. The impurities in the waste swarf and Al drossDross were found to affect the Co and Li products and their separation mechanism.

The manufacturingManufacturing sector depends mainly on the foundation industriesFoundation industries which have a major contribution to the country’s economy. These foundation industriesFoundation industries include glass, metals, ceramics, cement, paper, and chemical sectors that support the demands of our modern lives. On the other hand, these industries are energy intensive. Energy requirements in foundation industriesFoundation industries can be improved by benchmarkingBenchmarking and comparing the actual energy consumptionEnergy consumption of individual processes with their theoretical minimum value. In this study, an energy taxonomy approach has been used to identify the elements responsible for energy consumptionEnergy consumption in the granulation process. Bond’s law has been used to calculate the theoretical minimum energy consumptionEnergy consumption of one such individual process, i.e., granulation—a common process among the foundation industriesFoundation industries which accounts for an average of 50% of the total energy consumptionEnergy consumption. A framework has also been developed that can be used by foundation industriesFoundation industries to benchmark their energy efficiencyEnergy efficiency and that provides an insight into the practical and theoretical potential for reducing their energy requirements.

The Harris process for lead softeningLead softening uses sodium hydroxide and sodium nitrate to remove arsenicArsenic, tinTin, and antimony from molten leadLead by oxidation. It is known to be better than oxygen softening; however, the process has a higher cost in terms of the reagents used. Sodium hydroxide is corrosive and expensive. In this research, calcium carbonate, calcium hydroxide, and magnesium hydroxide were used as alternatives for sodium hydroxide in the softening process. Based on the initial results, the research focused on using calcium carbonate for subsequent softening process. In this study, the activities of the impurities, arsenicArsenic, tinTin, and antimony, were calculated and compared with that obtained with sodium hydroxide as the melt. The softening experiments were conducted on lead bullionLead bullion by design of experiment (DOE) method by varying temperature, time, and reagent quantity. The drossDross obtained was analyzed chemically and with X-ray diffraction (XRD) to identify the phases formed. Experimental and theoretical results are presented.

Copper slagCopper slag is a major waste produced in pyrometallurgical plants during the smelting and converting operations and has caused heavy environmental contamination. A pyro-hydrometallurgical process for the treatment of copper slagCopper slag has been developed to accomplish recovery of nickelNickel, cobaltCobalt, and copperCopper and reuse of iron source. It was proved that the slag phase was reconstructed by sulfation-sulfate decomposition roastingRoasting followed by water leachingLeaching, over 95% iron existing as hematiteHematite was transferred into residues which were subsequently to produce iron concentratesConcentrate. Nickel-cobalt mixed hydroxide precipitate was obtained from liquors after the separations of copperCopper, iron, and aluminum step by step. By adding concentrated HCl to re-dissolve the precipitate, then cobalt was extracted over nickelNickel using extraction agent N235 and the raffinate was subsequently crystallized to produce nickelNickel chloride by introducing HCl gas. On the basis of the optimum conditions from a laboratory-scale test, about 70% of copperCopper, nickelNickel, and cobaltCobalt were recovered as respective product, indicating the feasibility of the process.

TungstenTungsten is one of the most important refractory metals as it is used in the production of numerous end use items such as tungstenTungsten and tungstenTungsten carbide parts. Tungsten is also used in the manufacturingManufacturing of steels, super alloys, and catalysts. Other applications of tungstenTungsten are in the manufacturingManufacturing of tungstenTungsten-copperCopper and tungstenTungsten-silver composites. Tungsten from its concentratesConcentrate and secondary sources is processed as high-purity ammonium para tungstateAmmonium Para Tungstate (APT). Currently, there are two main APT production processes: one uses solid ion exchange and the other uses liquid ion exchange. Both processes use multiple process steps and generate large amount of process wastewater. Other serious problem of APT production is the difficulty in the availability of tungstenTungsten sources especially to the plants outside China. The ore concentratesConcentrate available to some tungsten processors in the market may be low grade ores and/or the high grade ores containing large amount of critical impurities such as Mo and/or radioactive elements. This paper will discuss some of these issues and also some process-related issues such as equipment scaling, loss of LIXLIX solvents, tungstenTungsten losses in the overall process, and large volume of process waste water, especially in the solid ion exchange method. Due to the proprietary nature of the work, literature from only presentations and publications will be presented. This paper will also discuss the recent literature, related to new conceptual APT process which could leadLead to increased efficiency, energy reduction, and waste minimization.

In this study, an efficient and sustainable hydrometallurgical process was developed for the recovery of zinc, bismuthBismuth, and leadLead from zinc-rich dustZinc-rich dust after pyrometallurgical treatment of iron and steel metallurgical dust. The feasibility of the separation of zinc, bismuthBismuth, and leadLead in the leachingLeaching system was confirmed by thermodynamic analysis. In the first step of the leaching process, zinc is leached and recovered as ZnSO4 in the leachate. In the second leachingLeaching step, a combination of H2SO4 and NaCl was used as leachingLeaching agent to study the leaching behavior of bismuthBismuth and leadLead under different experimental conditions (e.g., H2SO4 concentration, NaCl concentration, liquid-solid ratio, temperature, and reaction time). Under the optimum conditions, the leachingLeaching rates of bismuthBismuth and leadLead were 93.5% and 0.24%, respectively. The leachate enriched in bismuthBismuth was used to prepare bismuthBismuth products, and the leach residue enriched in leadLead could be further processed to recover leadLead.

Alloy powderAlloy powder is a typical by-product produced from stainless steel processing, which contains a significant level of valuable metals, such as iron, chrome, and nickelNickel. About 1 million tons of alloy powderAlloy powder are generated in China annually, but as mixed with impurities such as Al and Si, alloy powder is not suitable to be directly smelted into stainless steel by refining. In this study, alloy powderAlloy powder was efficiently utilized during limonitic lateriteLimonitic laterite sinteringSintering process. The effects of adding alloy powder on green bed permeability, the yield and quality indexes of the sinters, and the microstructure of the sinters were evaluated. The results show that the concentrated distribution degree of granules and green bed permeability was improved after adding alloy powderAlloy powder. As the additional amount of alloy powderAlloy powder increased from 0 to 3%, the tumble index and yield of the sinters rose from 50.07% to 54.69% and from 62.04% to 67.35%, respectively.

In this work, novel deep eutectic solventDeep eutectic solvent (DES) was prepared from the choline chlorideCholine Chloride as a hydrogenHydrogen-bond acceptor in combination with organic acidsOrganic Acid (i.e., phthalic acid, 2,2-dimethylol propionic acid, glutamic acid, tartaric acid) as a hydrogenHydrogen-bond donor. Only at the preparation temperature of 110 °C, two novel of DESs were prepared: choline chlorideCholine Chloride:2,2-dimethylol propionic acid with molar ratios of 1:0.67 and the choline chlorideCholine Chloride:tartaric acid at a 1:0.5 molar ratio. The thermal stability of DESs was studied. DESs choline chlorideCholine Chloride:2,2-dimethylol propionic acid (1:0.67) and choline chlorideCholine Chloride:tartaric acid (1:0.5) were found stable at temperatures lower than 211 and 195 °C respectively. The solubility of metal oxides (MOs) ZnO, Fe2O3, Fe3O4, and V2O5 was determined in choline chlorideCholine Chloride:2,2-dimethylol propionic acid (1:0.67) and choline chlorideCholine Chloride: tartaric acid (1:0.5). The obtained MOs solubility values indicated these novel DESs with the interesting ability to dissolve the selected MOs.

An understanding of the reaction phases formed during the high-temperature oxidationHigh-temperature oxidation of rare earthRare earth permanent magnets is vital for developing appropriate strategies for their pyrometallurgy-based recyclingRecycling processes aimed at the concentration and potential recovery of the rare earthRare earth elements. The current study uses in-situ high-temperature optical microscopy combined with ex-situ scanning electron microscopy to analyze oxide growth on the surface of an end-of-life Ni/Cu/Ni-coated NdFeB permanent magnet oxidized at 900 and 1100 °C for up to 4 h under ambient air conditions. Distinct oxide morphologies were observed at the two oxidation temperatures over time ranging from blister- and spike-like structures. At the longest oxidation times, visible cracking of the surface of the magnet and protrusion of Fe2O3 phase were observed. The presence of a Ni/Cu/Ni coating on the magnets was found to significantly affect the oxidation growth; a nickelNickel ferrite phase was formed at 1100 °C after 4 h while at 900 °C, there was still discrete NiO and Fe2O3.

Crystallisation is an important industrial unit operation for raw product formation, purification, and waste removal. This process typically requires multiple steps (crystallisation, solid liquid separation, and product drying) to attain the final product. Here, we introduce a novel process: membrane percrystallisationPercrystallisation which achieves complete separation of solvent from solute in a single step. Liquid is vaporised at the inorganic membrane permeate surface, whilst dry solid product is continuously ejected from the permeate surface, under vacuum. This novel technology has been demonstrated at the laboratory scale in metal recovery and waste brine treatment applications. Membrane percrystallisationPercrystallisation intensifies the process offering a simple, compact, and closed system. Within this study, key percrystallisationPercrystallisation operating parameters in salt crystallisation that employ supported continuous saccharidesSaccharide-based carbon membranesCarbon membrane will be discussed with examples of potential applications in hydrometallurgical processes.

IronIron (Fe), being such an abundant element, is used in various industries such as the steel industry. Similarly, arsenicArsenic (As) can be treated to obtain an industrially useful by-product. For this reason, the leachingLeaching of arsenopyrite (FeAsS) from mining tailingsTailings is silvered, using ThioureaThiourea (CH4N2S)-OxalateOxalate (C2O42−) system. The presence of FeAsS was confirmed by XRD and SEM–EDS, while the ICP analysis indicated a content of 5.47% Fe and 0.93% As. Likewise, the parameters analyzed were [CH4N2S] and [C2O42−]. As a result, the highest recovery of Fe was 21.29% and As of 24.04%, in concentrations of ThioureaThiourea of 0.03 mol and OxalateOxalate of 0.1 mol, at 60 min.

Based on the harmless and resourceful treatment of zinc-containing electric furnace dustElectric furnace dust, the orthogonal design of 4 factors and 3 levels was used to explore the effect of citric acidCitric acid leachingLeaching experimental conditions on the leaching rate of Zn, Fe, Pb, and other components. When the acid concentration is 0.8 mol/l, the leachingLeaching temperature is 55 ℃, the liquid–solid ratio is 8, and the leachingLeaching time is 60 min, the leachingLeaching rates of Zn and Fe are 82.2 and 13.71%, and the removal rates of Pb, S, and P are 93.08, 86.4, and 73.9%. According to experimental and theoretical research, zinc can be extracted from zinc-containing electric furnace dustElectric furnace dust, and a leaching residue with Fe content of 48.2% can be produced, which can be returned to the iron and steel process for recyclingRecycling. The test results can provide reference for the comprehensive development and utilization of zinc-containing electric furnace dustElectric furnace dust.

The concept of heating strength of sinteringSintering surface is introduced, which is used as the evaluation standard of sinteringSintering ignition effect. At the same time, ignition systemIgnition system in Shougang Jingtang sintering machine (550 m2) was studied and analyzed. The results showed that, with the increase of air–fuel ratio (A/F)Air-fuel ratio, the high temperature (above 1000 ℃) holding time was extended on the sinteringSintering bed surface at the condition of fixed gas flow in ignition chamber. The maximum temperature also rose, which means that the heating strength of sintering bed increased and the ignition effect improved. By increasing air–fuel ratio (A/F)Air-fuel ratio, the coke oven gas consumption decreased by 247 Nm3/h, and the sinter qualitySinter quality index remained stable in Shougang Jingtang Company.

In order to solve the problems of high cost, high risk, and serious environmental pollution in the current treatment of molten casting residue slagCasting residue slag and some of the casting residue slagCasting residue slag still cannot be effectively utilized, the molten casting residue slagCasting residue slag is treated by gas quenching technologyGas quenching technology to prepare slag wool fibersSlag wool fibers in this paper. The mechanism of fiberizationFiberization of molten casting residue slagCasting residue slag in the process of gas quenching is analyzed. The results show that the acidity coefficientAcidity coefficient of the prepared casting residue slagCasting residue slag fibers is 1.25. The total content of SiO2, Al2O3, CaO, and MgO was 93.25%. The slag wool fibersSlag wool fibers with fibers diameter less than 3 μm is 54.57%. This proportion decreases as the fibers diameter increases. 84.07% of slag wool fibersSlag wool fibers diameter is less than 7 μm. The results show that the molten casting residue slagCasting residue slag can be prepared into the slag wool fibersSlag wool fibers that meet the application requirements by gas quenching technologyGas quenching technology.

Rare earthsRare earth are critical to the future of green technology, especially for wind turbines and electric vehicle motors. However, reducing these rare earthsRare earth into the metals is challenging metallurgically and economically. An overview will be given on the state-of-the-art processes for reducing rare earthsRare earth from the rare earth oxides to the rare earthRare earth metal. The benefits and the challenges of the state-of-the art processes will be presented. An overview of novel processes being developed in the field will also be given. These novel processes range from innovations in metallothermic reduction and molten fluoride electrolysis to ionic liquidIonic Liquid electrolysis of rare earthRare earth oxides and attempts of reducing rare earthRare earth oxides using solid oxide membrane electrolysis. This lays the foundation for direction of future trends on commercial rare earthRare earth reduction technology.

Blast furnace dust (BFDBlast furnace dust (BFD)) is a kind of solid waste generated in the ironmaking process. It contains approximately 0.1% of bismuthBismuth (Bi). To reduce environmental pollution and storage problems associated with BFDBlast furnace dust (BFD), direct reduction process to recover Bi from BFDBlast furnace dust (BFD) was proposed in this study. Thermodynamic calculations and thermogravimetric analysis were first used to determine the initial reaction temperature between Bi2O3 and C. High-purity Bi2O3 and graphite were evenly mixed that the carbon to oxygen ratio is 0.4, 0.6, 0.8, respectively and heated at 800–1200 °C under 50 °C gradient for 2 h. Experimental results showed that almost all bismuthBismuth volatilized at 1200 °C and Bi and BiO could be obtained in the condensation zone by carbothermal reductionCarbothermal reduction. Therefore, this study provides a new and potential useful technology for recovery of Bi from BFDBlast furnace dust (BFD), as well as a certain practical approach to comprehensively utilizing such metallurgical solid waste.

The digitalisation of the world and electrification of transportation have been driving the increased usage of rechargeable batteries in the past decade. RecyclingRecycling and recovering valuable metals from Li-ion batteries waste is critical for securing the resources to meet the future demand and production of batteries. In this study, recyclingRecycling of a battery waste, a black mass containing multiple metals from the cathode and carbon anode, was evaluated using a pyrometallurgical route. Reduction of battery cathode material using carbon from the anode combined with hydrogenHydrogen as reductant was systematically investigated at 400–1000 °C. The study included thermodynamic assessmentThermodynamic assessment using the FactSage™ thermochemical package combined with selected experimental results. The overall reduction mechanismReduction mechanism was found to be uniquely characterized by the reduction temperature. The data and information obtained can be employed to develop and optimize the recyclingRecycling process of Li-ion batteries.

Separation of tungsten (W) and vanadiumVanadium (V) is of great significance for the utilization of the polymetallic complex minerals and secondary resources of these elements. In this work, selective extraction of V from sodium tungstateSodium tungstate solution was investigated using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507P507) as an extractant. The extraction process was studied to optimize various parameters including initial pH, extractant concentration, phase ratio (O/A), temperature, and contact time. The simulation calculation indicated W and V exist in the form of cation HW7O245− and anion VO2+, respectively, in solutions with pH ranging from 1 to 3, which provided a theoretical basis for the selective separation of W and V. In addition, under the optimum conditions (pH = 1.5, 20% (v/v) P507, O/A = 1/2, room temperature, and T = 20 min), the removal efficiency of V exceeds 90% with W loss below 6%.

Landfilling of spent alkaline batteries is considered as more attractive than recyclingRecycling if economic perspective is the main factor taken into account. The current study explores the potential use of solar thermalSolar Thermal energy in recovering valuable Zn/ZnO from the batteries in attempt to improve the economic competitiveness of the recyclingRecycling process. The black mass obtained from the batteries’ anode and cathode, mixed with carbon from end-of-life lithium batteries, was subjected to carbothermal reductionCarbothermal reduction at 1030 °C in a solar thermalSolar Thermal simulator under argon. It was found that high purity Zn/ZnO powder can be recovered from the black mass, leaving valuable MnO in the reactor. The increase in argon flow was found to decrease the particle size of the Zn/ZnO powder, where the average of 2 μm obtained at 2 L/min argon. Since potassium is the main impurity in the recovered powder, neutral leachingLeaching of the black mass prior to reaction may improve product’s purity.

On some situations, environmentally hazardous phosphatePhosphate ions exist in hydrometallurgyHydrometallurgy waste liquidsWaste liquid. Among the available treatment technologies, adsorbing colloid flotationAdsorbing colloid flotation (ACF) has been considered and is of particular importance. In this work, ferric chloride was used as colloid adsorbent and sodium dodecyl sulfate (SDS) as collector to remove phosphatePhosphate from the hydrometallurgyHydrometallurgy waste liquidWaste liquid by flotation. Different parameters, including solution pH, contact time, molar ratio, and collector concentration, were comprehensively investigated. The optimum phosphatePhosphate removal efficiency was 96.05% when Fe/P molar ratio of 2:1, contact time of 30 min, solution pH of 4, and collector concentration of 160 mg/L were applied. The results indicated that adsorbing colloid flotationAdsorbing colloid flotation can effectively remove phosphatePhosphate from solution and has great application prospects in hydrometallurgyHydrometallurgy waste liquidWaste liquid treatment.