12th International Copper Conference

Table of Contents

1. Hydrometallurgy

   1. Frontmatter

   2. Benefits of Shell GTL Mining Diluents in Copper SX for Low-Grade Copper Ore

      Miguel Rivera-Torrente, Nick Lokum

      Abstract

      Shell GTL G75, G80 and G85 are synthetic, aliphatic mining fluids supplied by Shell for copper solvent extraction (CuSX) operations which represents the 4th generation of SX diluents. Shell GTL fluids are produced from natural gas via the gas-to-liquids (GTL) process, resulting in a unique mixture of hydrocarbon distillate different from common market diluents. Laboratory tests of different blends under common operating SX conditions showed about 5–20% faster phase disengagement. This was associated to the complex interplay between viscosity, density, and hydrocarbon composition of linear and lightly (methyl, ethyl) branched iso-paraffins, as opposed to other diluents which may contain naphthenes and aromatics. The evaporation rate was lower than common aromatic and de-aromatized diluents, likely resulting in less top-up necessary.

   3. Mixing Theory and Application in Solvent Extraction with Opposing Impinging Flows and Static Mixers

      Francis Dakubo

      Abstract

      Solvent extraction (SX) is crucial in hydrometallurgical operations, particularly metal recovery from leach solutions. Conventional SX systems rely on mechanical mixers, often resulting in energy losses due to inefficient fluid interactions. This study explores the potential of impinging flow technology, complemented by static mixers, to enhance mass transfer efficiency and reduce energy consumption. By leveraging the kinetic energy of pumped fluids, we demonstrate that opposing impinging flow systems can achieve extraction efficiencies comparable to those of traditional pump mixers while minimizing operational costs. The research integrates Python simulations and experimental validations to quantify improvements in extraction efficiency. The findings indicate that opposing impinging flow combined with static mixing can achieve the same extraction efficiency as a mechanical mixing system (i.e., 35–50% for a single primary mixing conventional system). This suggests that primary mixers in a three-stage mixer-settle system may be unnecessary in some SX configurations. This study provides a framework for optimizing SX processes, making them more energy-efficient and sustainable.

   4. Effect of the Jetti Catalyst on the Dissolution of Chalcopyrite and Bornite—A Chemical and Electrochemical Analysis

      Zihe Ren, Chihwei Chao, Dave Dixon, John Uhrie, Nelson Mora

      Abstract

      Using pulverized, pure mineral specimens, the Jetti leach catalyst is shown to increase leach kinetics of both chalcopyrite and bornite where after 24 h, copper recovery increased from 10 to 39% on chalcopyrite and from 39 to 79% for the bornite sample studied. Under conventional acid-ferric sulfate leaching, bornite leaches in two stages, a rapid first stage kinetic where approximately 30% of the copper is leached until a passive Cu₂FeS₂ phase is formed. This passive condition is also seen in chalcopyrite leaching; however, second stage bornite remains more active than chalcopyrite as shown through lower rest potential and smaller potential difference (ΔOCP = OCP2-OCP1). Leach kinetics are independent of ORP within the range of 480–540 mV versus Saturated Ag/AgCl.

   5. Forty Years of Nitrogen Species Catalyzed Pressure Leaching

      Corby G. Anderson

      Abstract

      Forty years ago, industrially proven and applied nitrogen species catalyzed (i.e. NSC) acidic pressure leaching was commercialized on an industrial scale. It has been utilized to treat a number of ores, concentrates and recycled materials. This versatile technology offers many advantages including low temperatures, low pressures, low capital costs, low operating costs, faster throughput and less costly materials of construction than conventional pressure oxidation. This paper will elucidate the application of this technology for production of gold, silver, palladium, rhodium, zinc, germanium, gallium, cobalt, copper and nickel. Recycled material applications will also be elucidated. In addition, details of an application for treatment of a refractory chalcopyrite copper and gold bearing ore will be presented and pertinent economics discussed. Finally, details concerning a future demonstration plant with a continuous reactor will be elucidated.

   6. Dynamic Modeling of the MantoVerde Heap Leach Operation

      Todd Harvey, Peter Amelunxen, Brandon Akerstrom, Alex Holtzapple

      Abstract

      The MantoVerde project is a copper heap leach operation located in Chile, comprising four separate heap leach pads, three of which are permanent and one that is dynamic (on/off). Pregnant leach solution (PLS) is pumped to a common copper solvent extraction-electrowinning circuit. Original dynamic models built using METSIM® included all unit operations associated with the operation, as well as the past and forecasted ore tons and grade schedule for ore stacked on the heap leach pads. From this base-case model, two proposed scenarios were included: (i) the conversion to a bioleach via air and bacteria addition; and (ii) a new pyrite concentrate feed stream at 30% w/w moisture to the dynamic heap leach pad with a cobalt bleed circuit for mixed-hydroxide precipitate (MHP) production. Both scenarios have been built from the base-case model as a single simulation to provide a tool for dynamic water balancing and solution management, as well as copper and cobalt production forecasting. Understanding and quantifying the chemistry throughout the process was key, both within the heap leach system as well as for all stages of the downstream hydrometallurgical processing. For heap leach reactions, tools available within the METSIM® simulation software were used to determine kinetic reaction coefficients based on column test results, which were applied to each mineral for each ore type throughout the stacking and leaching process. Isotherm data for the SX circuit was incorporated into the simulation to determine overall extraction efficiencies, while assumed reaction extents were applied to the remaining processing steps, including copper precipitation (from the cobalt bleed PLS), ion exchange (Co, Ni, Cu, Zn, Fe, Al, Mg, Mn), and MHP precipitation (Co, Cu, Fe, Ni, Zn). Finally, solution chemistry was then studied in detail with the use of the OLI software for electrolyte equilibrium, specifically for iron precipitation within the heaps, copper precipitation from the cobalt PLS stream, and finally the MHP precipitation stage.

   7. Byproduct Oxygen Capture for Accelerated Digestion and Processing of E-Waste

      Harshit Gautam, Kamlesh Melana, Suresh Balakrishnan

      Abstract

      The volume of e-waste is growing rapidly. There are many processes that are currently being developed for processing e-waste to recover plastics, copper, gold, silver, PGMs, and other components. In almost all cases efficiencies are improving as well as reduction in carbon footprint. For large scale processing at central locations, the typical smelting and electrorefining options offer cost effective recovery of copper, gold, and other metals. Hydrometallurgical processing can typically be applied on a smaller and more localized scale. However, it has typically had two main drawbacks preventing adoption for commercial processing of e-waste on a reasonable scale.

      (i) It is important to have near complete recovery of copper and gold/PGMs in order to compete with smelting and refining. This typically requires several different chemistries to be used for the various metals and flowsheets can become quite complex.

      (ii) The requirement for oxidants to be used with the different lixiviants which are often costly, dangerous to handle, have significant carbon footprint or cause water balance problems preventing the overall processes from meeting environmental targets.

      While gold is typically the most valuable component of e-waste it is copper that is generally the highest by weight after the plastics, glass, and steel are removed. Past studies indicates that several key factors for digesting copper such as type of oxidant, temperature, pretreatment, solid to liquid ratio, acid concentration, starting solution conditions, particle size and catalysts such as copper and iron were studied for an e-waste metals concentrate to identify optimum and sustainable conditions for copper recovery and gold concentration. It is well known and published that oxidants such as nitric acid and hydrogen peroxide offer rapid digestion rates however they can have significant environmental impact. Oxidants such as oxygen and ozone offer advantages over air digestion however require energy to generate in situ. Relative copper digestion rates for the various oxidants in sulfuric acid for a given e-waste metals concentrate with <5 mm particle size were 30–60 g/L/h for hydrogen peroxide, 5–10 g/L/h for oxygen, and 1–5 g/L/h for air. Higher temperature and smaller particle size improve rates as does starting with copper in solution. Pretreatment to remove base metals such as tin, iron, zinc, and aluminum increases the initial digestion rate. Using a closed vortex electrowinning cell high purity copper was recovered and acid regenerated. Byproduct oxygen generated in the cell at the anode can be used for digestion enhancement. Test results showed 4.4 × faster digestion rates with byproduct oxygen than air sparging similar to the results using pure oxygen. It is expected that this mechanism may also be utilized in heap leach mines to boost leaching recovery rates and increase mine production for close to zero additional reagent cost.

   8. Copper Solvent Extraction: 2025 Global Survey of Operating Practice and Performance

      Kathryn C. Sole, Tyler McCullum, Andrew Nisbett, Jacklyn Steeples, Dongliang Huang

      Abstract

      Global surveys of operating practice and trends in copper solvent extraction have regularly been carried out since 1997. This paper reports and evaluates the outcomes of the ninth survey in this series, based on individual plant operating data for 2024. Trends in feed and electrolyte compositions, and consequent selection of extractant and diluent are reviewed, with their corresponding impacts on copper recovery and operating costs. Differences in operating practices in different parts of the world are compared. Strategies for optimization and maximizing copper transfer and copper production with changing feed compositions during life of mine and with regional differences in mineralogy are discussed. The evolution of extractant formulations and trends in equipment design and configurations are also assessed.

   9. The Halion Loop™—Expanding the Applications of Halide Hydrometallurgy

      Dave Sammut

      Abstract

      Chloride hydrometallurgy has been internationally established as offering faster and cheaper extraction of copper and other metals from mineral ores, concentrates and tailings than any sulphate-based hydrometallurgy approach. However, efficient recovery from the chloride liquor has proven elusive. The Halion Loop™ process leverages proven leaching technology to achieve economically competitive high levels of extraction of target metals at atmospheric pressure and <100 °C, using air as its primary reagent. The process is based on the use of mixed halides: chloride and bromide. It adds more recent innovations to expand the capabilities of both metals extraction and recovery. Loop Hydrometallurgy has ‘closed the loop’ for an effective and continuous process cycle via the invention of the breakthrough Halion™ electrowinning cell. This is the first copper recovery technology for the effective and practical recovery of dendritic copper from the cuprous state. Unlike conventional electrowinning, which requires removal and stripping of cathodes every 2–3 days, the Halion™ cell is designed to operate 24/7 for up to 12 months continuously. Requiring only one electron per copper atom, this new design could reduce power consumption of electrowinning by up to 70%. Since 2023, Loop Hydrometallurgy has been significantly expanding the effective range of source materials. It has shown that the Halion Loop™ can viably process coarse, low-grade, polymetallic and/or arsenic contaminated resources, including direct ore processing. Leveraging the massive savings that Halion Loop™ enhanced processing can offer by reducing mill operations, multiple studies have shown that miners can produce high purity copper metal at site for less than the current cost of producing conventional smelter-grade concentrate. This paper will report results from studies expanding the range of project feedstocks that can be economically and effectively processed: coarse rougher concentrates, low-grade bulk polymetallic concentrates, high grade copper ores and more.

   10. Removal of Iron Contaminant in the Cemented Copper from an Iron Laden Copper Ore

       Tajudeen Ayodele, Abraham Adeleke, Ayodele Daniyan

       Abstract

       The aim of this study was to reduce the high iron and aluminum content of an iron laden copper ore. The copper ore from Akiri in Nasarawa state, Nigeria was ground passing 250 µm sieve. X-ray fluorescence elemental analysis showed that the ground ore contain 4.68% copper and 11.33% iron. Scanning electron microscopy-energy dispersive X-ray spectroscopy point analysis of the ore showed that it contains 6.20, 6.40, 2.12, and 65.8% of titanium, manganese, aluminum and iron, respectively at the random point. The ore was subjected to agitated leaching with dilute sulphuric acid and the solid copper was recovered by cementation with zinc powder. The iron contaminant in the cemented copper was removed by digestion in a mixture of 0.5 M sulphuric acid and 0.1 M sodium carbonate solutions at 50 °C in a slurry of 10 percent solid, without stirring at a pH of 2 for 30 min. The purified copper was found to contain 97.20% copper and low constituents of iron, aluminum, manganese, chromium, vanadium, and silicon impurities of 0.79, 0.08%, 0.61, 0.02, 0.03, and 0.33%, respectively. The results obtained therefore showed thar most of the impurity elements in the ore were largely removed by the leaching, cementation and purification processes carried out.

   11. Modeling Ferric Leaching of Chalcocite in Heap Leaching Columns

       Chun-Wei Mo, David Dixon, Zihe Ren, Chih Wei Chao

       Abstract

       An axisymmetric model is developed to simulate water and solute transport in a column leaching system, incorporating advection, dispersion, adsorption, and chemical reactions. This study extends the model to include ferric leaching of chalcocite through a two-stage reaction process using experimentally derived parameters. The first stage follows a Type I–III hybrid leaching mechanism, while the second stage is governed by a Type I–II hybrid mechanism. Each captures key aspects of ferric ion interaction with chalcocite. The model is validated through a stepwise approach, including water transport, solute transport, and individual reaction stages. Simulations reveal spatial and temporal distributions of ferric ions, chalcocite-I, chalcocite-II, and copper concentrations. Results show that ferric is consumed rapidly in the first stage and more slowly in the second, affecting copper recovery. The model captures key transport and reaction behaviors consistent with expected leaching processes and provides a foundation for future integration of experimental data and extended simulations.

   12. Copper Extraction from Chalcopyrite with New Hydrometallurgical Systems

       Jaeheon Lee, Joseph Pearlman, Silvia Callisaya, Junmo Ahn, Jaeyeon Kim

       Abstract

       Copper is one of the latest additions to the list of critical minerals designated by US Department of Energy due to increasing demand for electrification and cloud storage. The expected copper demand in 2050 will be more than 60 million tons while the current mine production was only 22 million tons in 2023. Due to the consistent delays in permitting new world class mines and processing plants, it would be extremely difficult to triple the mine production in less than 30 years. Low grade materials for heap or dump leaching play key roles to meet the metal demand. These primary sulfides can only be processed by the process with low capital and operating costs. New chemical systems or processing methods have been investigated varying from chemical and biological processes. The authors have studied systems using conventional sulfuric acids, methane sulfonic acids, and glycine with various oxidants and additives such as activated carbon. It’s been observed that in a well-controlled temperature regime and solution chemistry, copper extraction was not hindered by the well-known passivation. It is believed that proper control and maintenance of the solution Eh played a key role in avoiding the surface passivation. From chalcopyrite concentrate, 99% copper extraction was observed at 65 °C and low grade ore also showed promising results in room temperature leaching with activated carbon. Methanesulfonic acid also showed excellent results and the downstream solvent extraction in methanesulfonic acid was also investigated.

   13. Electronic Structure or Passivation: What's the Story with Chalcopyrite?

       F. K. Crundwell

       Abstract

       The dissolution of chalcopyrite is often viewed in terms of passivation. This interpretation has frequently ignored the electronic structure of the mineral, instead treating it simply as a source or sink for electrons. An alternative explanation has been pursued by Crundwell and co-workers, who have presented significant data and analysis to support their views. This alternative viewpoint argues that the events concerning charge-transfer at the interface must be interpreted in terms of the electronic structure of the mineral itself. These authors have argued that this viewpoint is more consistent with the mechanism of the dissolution of other minerals. In this paper, we critically review these opposing viewpoints.

   14. Using the Ferric for Leaching Sulfides—CEMIN and Ecowinning Technologies Experience

       Roberto Vergara, Miguel Ángel Sarria, Jaime Roberto Simpson, Victor Manuel Vidaurre, Hector Vilches

       Abstract

       Ecowinning Technologies tech is based on the generation of oxidizing agent ion ferric (Fe³⁺), by installing both a parallel process and/or modifying the existing electrowinning plant, while generating cathodes of the highest purity. Ecowinning Process™ patented technology consists in the use of ion exchange membranes, which oxidize the ferrous from the ILS (Intermediate Leachate Solution)/raffinate to produce ferric; all of this happen inside the specially adapted electrowinning cell. The company changes conventional anodes for its membrane encased devices to produce the reaction. At the same time, rich electrolyte is processed inside the cell in a separate reaction, obtaining 99.999% copper cathodes. Also, this process doesn’t produce acid mist and uses less energy than the conventional one. The presentation will explain further the process and share the real-life experience of the industrial modular plant installed inside CEMIN Planta Amalia operation. Ecowinning Technologies now produces 4 g/l of ferric for a flow of 3 m³/h of ILS coming from the Solvent Extraction (SX) plant. The plant is fully functional, and it works 24/7/365. The ferric produced is used to feed CEMIN’s agglomeration process, complementing chloride leaching, which has been used by the operation since 2020. Also, current results and potential applications in larger hydrometallurgical plants will be presented.

   15. Revolutionising Solvent Extraction: Advantages of the Modular Mixer-Settler Design

       S. Sewrathan, E. Mkhize

       Abstract

       The mining industry is ever-changing. Fluctuating commodity prices, increasing capital costs and variable complex ore grades are but a few factors driving the need for innovation. In the field of hydrometallurgy, modular mixer-settlers represent a significant advancement in solvent extraction technology, their operational flexibility making them suitable for integration at various stages in a process flow sheet. Modular mixer-settlers can process particularly low flow rates, as low as 0.5 m³/h, enhancing the efficiency and versatility of solvent extraction operations to meet specific plant needs. One of the key advantages of modular mixer-settlers is their prefabricated construction, which facilitates transportation to and installation on site. This prefabrication also significantly decreases the transport and construction costs, as modular units can be containerised and on-site assembly time is reduced. Furthermore, the units are designed to eliminate the need for extensive earthworks and concrete foundations, thereby providing additional cost savings and minimising environmental impacts. The key design features and applications of the modular mixer-settlers showcase how their unique attributes contribute to streamlined operations and improved cost-efficiency. This innovation is a pivotal development in solvent extraction, offering a flexible and efficient solution that can be easily scaled to meet the evolving demands of modern hydrometallurgical processes.

   16. Atmospheric Leaching of Complex Copper Concentrates and the Critical Role of Mineralogical Analysis

       Maysam Moham, Felipe Lagno, Henry Gordon, Don Shane

       Abstract

       The depletion of high-grade copper ores has led to increasingly complex mineralogy in copper sulfide concentrates, posing challenges for processes concentrates. Complex mineral phases hosting copper and elevated level of impurities demand more complicated treatment methods for efficiency and environmental compliance. Atmospheric leaching has emerged as a promising hydrometallurgical method for processing copper sulfide minerals, but its success hinges on the understanding of the mineralogical properties of the concentrate and selection of leaching conditions. This study explores a multi-stage atmospheric leaching process for a complex copper concentrate in a chloride-containing sulfate media. It highlights the critical role of mineralogy in selecting and optimizing the leaching conditions to enhance copper and silver recovery. The findings demonstrate the value of integrating mineralogical insights to improve recovery rates and tackle challenges associated with complex concentrates.

   17. Development of a Hydrometallurgical Arsenic Removal Process from Copper Concentrates

       Leslie Bryson, Michael Mittelstädt, Rakan Rahbani, Ricardo Pezoa, Marcelo Acuña, Cristian Calderón

       Abstract

       Aurubis AG and Codelco have been working together to develop a hydrometallurgical process to treat lower arsenic-bearing copper-concentrates: 0.5–2.5 wt.% As. This process aims to produce a “clean” concentrate with arsenic concentrations below 0.1 wt.% while disposing the arsenic as scorodite. This process primarily consists of leaching, crystallization, and oxidation stages to selectively remove arsenic from concentrates and produce a calcium arsenate intermediate in the “Aurubis Process” which is amenable to further low-cost conversion to scorodite in the process being operated by Ecometales (a subsidiary of Codelco) for over ten years now, the “EcoMetales Scorodite Process”. Scorodite is a stable compound with very low arsenic solubility and therefore preferred to dispose arsenic safely and has been classified by the Chilean government as non-hazardous waste. Laboratory test work underpinning the leaching, crystallization and oxidation processes has been performed by Aurubis’ R&D Department in Hamburg while the Arsenic fixation tests were performed by Ecometales laboratories in Calama, Chile. The process developed maximizes arsenic leach efficiency, using alkaline sulfide leach chemistry while optimizing reagent consumption and reuse. Copper concentrate from Chuquicamata (Chuqui), a major Codelco mine, containing 1.4% Arsenic, have been leached during the testwork trails, yielding arsenic leach efficiencies over 98% with Arsenic as low as 0.05 wt.% in the final “cleaned “concentrate . A sample of the arsenic intermediate produced during the teswork has been shipped to EcoMetales for further leaching and subsequent fixation as scorodite. The intermediate leach and scorodite residues have been environmentally evaluated, with both passing TCLP non-hazardous classification for arsenic. This paper will discuss the evolution of the Aurubis process by presenting the results from several test work stages, showing yields and product purities obtained. The results of the scorodite testwork fixation performed by EcoMetales will also be discussed, including TCLP results, and arsenic characterization. Arsenic rich copper concentrate deposits are available around the world. Unlocking this copper source will require a process that can recover the copper while ensuring the arsenic is deposited in a safe and environmentally sustainable way, preferably at the mine site.

   18. Recovery of Copper and Nickel from Sulfide Minerals Coupled with Atmospheric CO2 Sequestration

       Fei Wang, Mojtaba Adelalipour, Kourosh Javdantabar

       Abstract

       With the world in transition to a low-carbon economy, the needs in critical metals especially copper and nickel and in CO₂ sequestration are dramatically increasing. Chalcopyrite and pentlandite are important resources of copper and nickel resources, respectively. In addition to the copper and nickel from the sulfide minerals, the iron from chalcopyrite and pentlandite and the magnesium from the gangue minerals may be used to sequester CO₂ into iron and magnesium carbonates for permanent CO₂ storage while conventionally they are considered as impurities and are rejected as waste. In addition, the sulfide minerals in waste stockpiles usually induce a concern on potential acid mine drainage. In fact, the sulfur from sulfide minerals can be potentially utilized to directly capture CO₂ from air while maintaining the stockpiles in neutral to weakly alkaline conditions. This work presents a novel and sustainable approach that can selectively extract critical metals including copper and nickel from low-grade sulfide resources for enhanced critical metal recovery and to simultaneously achieve CO₂ mineralization for carbon-neutrality production. This novel process comprises the steps of leaching the feedstock comprising at least one of chalcopyrite, pentlandite, and gangue minerals in a leach solution producing a metals-containing leach solution, wherein the sulfide from the chalcopyrite, pentlandite, and iron-sulfide minerals sequesters CO₂ as bicarbonate ions and the iron from chalcopyrite and pentlandite or the magnesium from the gangue minerals sequesters CO₂ into iron and magnesium carbonates into the leach residue as stable CO₂ storage; recovering copper and nickel from the metal-containing leach solution producing high-value copper and nickel products and a copper and nickel depleted solution; and recycling the metal-depleted solution to the leaching step without chemical consumption. Therefore, this novel work for the integrated copper and nickel recovery from sulfide resources and CO₂ sequestration can make a significant contribution to the robust and sustainable production of copper and nickel and carbon neutrality.

   19. Subsurface Leaching of Copper Through Surfactant-Enhanced Acid Injection

       Rebecca Copp, Julius Heidlas, Dale Rucker, Brian Cubbage

       Abstract

       Subsurface leaching (SSL) through direct injection of acid to underperforming parts of a copper leach pad is well documented and proven effective at recovering metals. The potential of using leaching aids to enhance the rate and metal removal in SSL has not been extensively explored. For this work, a leaching aid was added as a direct feed to injection wells used for SSL in a copper leach pad. The effectiveness of the leaching aid was determined using solution samples and electrical resistivity geophysics along the surface. The addition of the leaching aid increased copper grades compared to long-term injection without the leaching aid.

   20. Use of Coagulant for Silica Removal Ahead of Solvent Extraction Plant: Comparative Laboratory Case Studies Using Cationic Polyamine Versus Neutral Polyether Chemistries

       Patty Bwando

       Abstract

       Many Democratic Republic of the Congo (DRC) hydrometallurgical plants are confronted with the presence of silica which is one of the deleterious elements co-extracted into the pregnant leach solution (PLS) from leaching to solvent extraction (SX) where it can cause operational issues. Levels of this impurity can vary from one plant to another, and for the same operation they might fluctuate over time depending on the tenor in the plant feed material and leaching conditions. Higher concentrations of silica in PLS, usually above 500 ppm, are known to increase crud formation, cause slow phase disengagement times and instabilities of the desired mixer’s organic continuity, and thus reduced plant operating capacity due to increased entrainment and crud run. Various coagulant chemistries have been introduced to the DRC hydrometallurgical industry in the past 10 years, some of them were considered for laboratory trials while few among them were selected for plant applications. Different silica elimination levels were achieved depending on the nature of the product, the dosage and addition point. Varied impacts were noticed on downstream processes: Solid liquid separation (SLS) and SX. This paper discusses the observations made during comparative laboratory testing works in different hydrometallurgical plants, and the implications of using two different products, i.e. cationic polyamine and neutral polyether coagulants.

   21. Regeneration of Ferric by Hydrogen Peroxide for Heap Leaching of Copper Secondary Sulfides

       R. Winarko, W. Liu, D. B. Dreisinger

       Abstract

       Heap leaching is considered a cost-effective hydrometallurgical technique for extracting copper from low-grade copper sulfide ores. In the oxidative leaching of copper sulfides, an oxidant, typically ferric, must be continuously supplied to the mineral surfaces for the leaching reactions to proceed. Ferric as the oxidant can be regenerated within the heap via bacterial-assisted oxidation of ferrous by oxygen or outside the heap using other oxidants, such as hydrogen peroxide. In situations where conventional bacterial oxidation of ferrous is ineffective—particularly when the process water contains elevated concentrations of chloride—the use of hydrogen peroxide for the ex-situ regeneration of ferric could be an alternative. This research investigated the effectiveness of hydrogen peroxide in oxidizing ferrous in raffinate solutions to supply ferric for heap leaching of secondary copper sulfides. Reactor tests were first carried out to quantify ferrous oxidation rate at different solution compositions, followed by column leaching tests of a copper ore containing secondary sulfides. The experimental results show that ferrous could be effectively oxidized by hydrogen peroxide. The presence of chloride in solution did not affect the extent of oxidation. The presence of copper slowed down the oxidation. Column leaching tests demonstrated that the copper extraction from the secondary sulfide ore was satisfactory, and ferric was effectively regenerated with the addition of hydrogen peroxide. The research findings could help heap leach operations manage oxidant regeneration using hydrogen peroxide for heap leaching of chalcocite, especially at elevated concentrations of chloride.

   22. Assessment of Copper Concentrate Processing Technologies—Flowsheet Development and Energy and Mass Balance Calculations

       R. Winarko, W. Liu, D. B. Dreisinger, Brenton Atkins, Debbie Erasmus

       Abstract

       Copper sulfide ores are conventionally processed via flotation, smelting, converting, and refining. Though well-established, the conventional process is not suited to treatment of copper concentrates containing high levels of impurities, such as arsenic. Various hydrometallurgical technologies have been developed to process these high impurity copper concentrates. This study conducted a comprehensive review of existing copper concentrate leaching technologies. These technologies were broadly categorized into bioleaching and chemical leaching. Chemical leaching was further divided into low (<119 ºC), medium (119–159 ºC), and high temperature (>190 ºC) in sulfate media, chloride leaching, and leaching with ammonia and other lixiviants. For each technology, the following information is reviewed: characteristics of feed materials (Cu, precious metals and impurities), particle size reduction, leaching conditions, copper recovery, iron removal, fate of sulfur, and impurities disposal. After the technology review, a scorecard was developed to evaluate and rank these technologies. The scorecard comprises five criteria—risk, reward, footprint, orebody suitability, and cost—each assigned a weight. Within each criterion, there is a set of key performance indicators, each with its own weight. The Albion process was then selected to demonstrate flowsheet development and mass and energy balance calculations.

   23. Recovering Abandoned Cobalt as a By-Product from the Raffinate in Copper SX-EW

       K. Takatsugi

       Abstract

       In the present study, the process of recovering Co from the SX raffinate of the Cu SX-EW operation was developed at the laboratory bench-scale. The proposed process consists of cementation pretreatment, ion-exchange, and purification steps in order to obtain marketable quality Co precipitates with a high recovery rate and low cost.

   24. The Effect of Chalcopyrite Composition on Semiconducting Properties

       Sarah Patterson, Julian Battaglia, Ariel Rieffer, Zafer Mutlu, Andrew Wessman, Isabel Barton

       Abstract

       Chalcopyrite (CuFeS₂) is a common copper ore mineral that displays variable but often poor leaching behavior under typical heap leach conditions. Ongoing research has provided inconsistent magnitudes of activation energy and dissolution mechanisms, even for chalcopyrite leached in the same chemical systems. This is possibly due to variations in crystallography, impurities such as Zn, Ag, Co, and Se, which natural chalcopyrite readily accommodates, or interference from additional sulfides, like cubanite, haycockite, mooihoekite, putoranite, or talnakhite, which have similar crystallographic signatures and optical properties. Additional contributors to these observations are unconstrained variations in chalcopyrite semiconducting properties, such as charge carrier type, density, and resistivity. Little is known about these in natural chalcopyrites. Currently, most natural chalcopyrites are considered n-type semiconductors, while an estimated 3–5% of the species are weak to moderate p-type; measured resistivities reported in the literature range from 10 ⁻⁵ to 150 Ω-cm. However, measurements of natural samples are uncommon and typically uncorrelated with composition. Previous attempts to correlate chalcopyrite composition and semiconducting properties have yielded ambiguous results, largely due to limited numbers of samples and limited methods of characterization. This paper reports preliminary results from an ongoing study of the relationship between chalcopyrite composition and semiconducting properties. The results shown are based on 9 whole-rock chalcopyrite samples, characterized by electron microprobe and four-probe station for sample composition, resistivity, charge carrier density, and resistivity. These natural rock samples were found to have averages of 4.11 Ω-cm resistivity (median 0.35 Ω-cm) and mobility of 15.09 cm²/V-sec (median 8.95 cm²/V-sec). These preliminary results show a potential inverse correlation between chalcopyrite Ag concentration and charge mobility, while other elements cover a wide range with no clear effects. This may be due to the effect of fine-scale non-chalcopyrite sulfide impurities in the samples, which affect the semiconducting properties, but not mineral composition measurements.

   25. Development of Copper and Gold Recovery Process from Oxide Ore by Two-Stage Leaching System

       Bobur Gayratov, Labone Godirilwe, Sanghee Jeon, Atsushi Shibayama

       Abstract

       In this study, a two-stage atmospheric leaching method was utilized to extract copper (Cu) and gold (Au) from a gold-bearing oxide copper ore. Acidic leaching using sulfuric acid (H₂SO₄) was initially employed to selectively extract copper, followed by alkaline leaching using sodium thiosulfate (Na₂S₂O₃) to extract gold from the solid residue. Various parameters were studied to achieve optimum leaching conditions, these include the effects of sulfuric acid concentration, temperature, and time for enhanced copper extraction, while concentrations of thiosulfate, ammonia, and copper ions as well as time were investigated for optimized gold extraction. The optimal copper extraction of 96% was obtained within 120 min of leaching at 60 °C with a sulfuric acid concentration of 0.5 M. Subsequently, in the investigation of ammoniacal thiosulphate leaching to extract gold from the residue, optimal conditions were found when using a mixture of thiosulfate, copper sulfate, and ammonia at concentrations of 0.4 M, 0.04 M, and 0.5 M, respectively. A gold extraction rate of 90% was achieved after 24 h of leaching at room temperature.

   26. Copper Extraction from Low-Grade Copper Tailings Using Resin in Moisturised Mix Technology

       Theophilus Amos-Judge, Pavel Spiridonov, Richmond Asamoah

       Abstract

       The rapid depletion of high-grade copper resources suggests that future copper supplies will likely rely more on low-grade ores, tailings, and other unconventional resources. This paper presents a series of extraction studies focused on a complex low-grade copper tailing, aiming to develop effective methods for improving copper mineral recovery and upgrading. Specifically, the study compares the efficacy of atmospheric leaching and resin-in-moist-mix methods to investigate the copper leaching behaviour from flotation tailings. These methods were assessed as part of an integrated process designed to valorise waste products by extracting valuable metals, such as copper. Leaching experiments were conducted under various conditions, using diluted sulfuric acid (H₂SO₄) as the primary lixiviant in both atmospheric and resin-in-moist-mix processes. The study evaluated the effects of different leaching parameters, including acid strength, solid loading, and time, on copper recovery. Additionally, the impact of resin volume on the performance of the resin-in-moist-mix method was also considered. Results revealed that, at acid strengths of 1 M and 3 M, copper recovery for atmospheric leaching increased from 55 to 60%, respectively. In contrast, copper recovery in the resin-in-moist-mix method decreased from 94 to 78% at the same acid concentrations. The effect of solid loading was significant in both methods. As solid loading increased from 30 to 40%, copper recovery decreased in both cases. Atmospheric leaching saw a reduction from 72 to 67%, while resin-in-moist-mix recovery dropped from 73 to 69%. Overall, the resin-in-moist-mix method demonstrated superior copper recovery across all tested conditions. The maximum recovery achieved by this method was 94%, compared to 72% with atmospheric leaching. This higher recovery is attributed to the resin’s increased capacity to capture copper ions in the pulp, which might otherwise go uncollected in the atmospheric leaching process. These findings underscore the resin-in-moist-mix method’s potential for efficiently recovering copper from low-grade resources, providing a valuable alternative as high-grade copper supplies continue to decline.

   27. The Management of Iron Transfer in the Solvent Extraction of STL

       Godfrey Mitshabu Bamuanya

       Abstract

       One of the big challenges of the solvent extraction unit of the hydrometallurgical operation of “La Société du Terril de Lubumbashi” in the Democratic Republic of Congo is the processing of a leach solution containing a relatively high level of iron (Fe) impurity in the electrolytic beneficiation of copper (Cu). The raw material is a granular white alloy containing mostly Fe, Cu, cobalt (Co), germanium and silver. The leaching strategy includes two steps. The bulk of the Fe is leached in a primary step together with Co. Cu is leached in a secondary leaching step together with germanium. This secondary leach solution contains up to 40 g/L of Fe, depending on the concentration of Fe in the fed white alloy. The solvent extraction mixers and settlers were sized to minimize the aqueous entrainment of the leach solution in the loaded organic. A washing stage of this loaded organic was included to mitigate the transfer of Fe among other impurities. Cu selectivity of the extractant over Fe is evaluated to be above 3000. A formal electrolyte bleed, and moreover a subsidiary portion of that bleed that would be recycled to the washing stage to make it run more as an Fe scrubbing rather than a physical washing stage was not fully anticipated in the design. We have run a mass balance exercise across the wash-strip-electrowinning circuit to quantify the electrolyte bleed required to control Fe concentration in the electrolyte around 1.5 g/L. The importance of a washing/scrubbing stage and a small electrolyte bleed is outlined.

   28. Integration of the Electrowinning Process for Copper Recovery with Resin in Moist Mix Process

       A. K. Guru, H. Pandya, M. Barretto, G. Acquah, P. Spiridonov, R. Asamoah

       Abstract

       The process conditions for efficient copper recovery from low-grade ores and fines are crucial for sustainable operations. This study employs an eco-efficient, novel Resin in Moist Mix (RIMM) process, integrating electrowinning to assess the impact of process parameters on copper recovery. This work utilized the Design of Experiments approach, where critical parameters such as current density, copper concentration, acid concentration, and deposition time were systematically analysed. It was observed that higher current densities increased copper deposition rates, though at lower purity, whereas lower densities yielded higher purity copper but at slower rates. Acid and copper concentrations exhibited minimal impact on both purity and deposition rate, highlighting the dominant role of current density. The study underscores the feasibility and optimization potential of electrowinning for high-quality copper recovery within the RIMM process.

   29. Technologies and Processes for Economical Recovery of Cu from Challenging Ores

       B. D. H. Knights

       Abstract

       Increasing demand for copper, along with decreasing availability of economic oxide and sulfide resources, is leading to alternative technologies being investigated to recover this important metal. Stockpiles of low-grade or refractory ore are advantageous since mining costs are significantly decreased. However, many such ore bodies have challenges, including high gangue acid consumption or low acid-soluble copper (ASCu). This paper explores various processing options available for such resources, highlighting the specific conditions under which they can be applied. Where technologies have not been applied industrially yet, the problems that must be addressed are described.

   30. Pressure Leaching of Copper Sulfide Concentrates

       Petteri Pesonen, Janne Karonen, Alexander Tuhkunen

       Abstract

       Copper oxide ores are depleting or running short in heap leaching process, releasing existing SX-EW capacity for additional PLS feed. Some oxidic ore mines have already converted the operations to process transition ores, i.e., mixed sulfide and oxide ores in existing heap leaching facilities, but the copper recovery rate, especially from primary sulfides, remains unsatisfactory. Copper pressure oxidation process (Cu POX) offers an effective and straightforward way to refine impure and chalcopyritic sulfidic copper concentrates to produce substitute pregnant leach solution (PLS) for the existing SX-EW plants to compensate the depleting oxidic heap leaching production. The sulfuric acid generated in the Cu POX leaching process can be utilized by recirculating the PLS in the existing heap leaching. Impurities like iron and arsenic have limited solubility in Cu POX leaching conditions. Typical precipitate for arsenic is scorodite and iron precipitates as hematite and basic iron sulfates. The complete copper pressure leaching process concept comprises autoclave pressure leaching for sulfidic copper concentrate to produce copper containing pregnant leach solution (PLS). The leaching process is followed by a neutralization step (or use of the acid in heap leaching facility), copper solvent extraction, and electrowinning operations. In addition, the flowsheet can be modified to recover gold and silver from the Cu POX leach residue.

   31. Real-Time Elemental Analysis to Enable Full Insights in the Composition of Hydrometallurgy Processes

       M. Zoontjes, M.-E. Provencher, A. Nijhuis, U. König

       Abstract

       Ongoing ore depletion necessitates more in-depth analysis to maintain processing efficiency as the quality and homogeneity of starting materials decline. While processing primary streams remains essential, incorporating secondary and recycled streams is increasingly important—not only to maximize operational output but also to support a sustainable future. Hydrometallurgy, which employs aqueous chemistry to extract metals from ores, is particularly useful for ores with lower-grade mineral content and for metals that are difficult to extract through traditional methods like smelting. This method is frequently applied for the extraction of metals such as copper, nickel, cobalt, gold, and rare earth elements. Applications range from heap leaching and solvent extraction to final electrowinning. These processes are known to be chemically and energetically demanding, with elemental concentration as a key parameter to control during processing.

   32. Economic Recovery of Copper from Small and Remote Deposits by Transportable Copper Sulphate Production Modules

       Michelle Weldhagen, Sergio Burelli

       Abstract

       Large ore deposits for the extraction of copper to support the green energy transition are becoming increasingly scarce, and small deposits at remote locations will be required to close the gap. However, the capital cost for conventional solvent extraction-electrowinning (SX-EW) is generally prohibitive to the economic recovery of copper from small and remote deposits. The infrastructure and power required for copper electrowinning are major cost contributors which adversely affect the feasibility of copper cathode production. Electrowinning (EW) plant and power costs can typically only be justified over an extended life of mine associated with large ore bodies. The production of copper sulphate as the pentahydrate (CuSO₄·5H₂O) is a viable alternative which reduces capital and operating costs by eliminating EW, thus enabling the economic processing of small and remote deposits. Copper is recovered from the pregnant leach solution (PLS) by means of a modified solvent extraction (SX) circuit, where copper saturation is achieved chemically in the stripping stages to precipitate copper sulphate. The copper sulphate is recovered from the strip solution by means of centrifuging, which produces a baggable dry product ready for transport. The large energy requirements associated with conventional evaporative or cooling crystallisation, and product drying, are therefore also eliminated. The electricity supply to support either electrowinning or conventional crystallisation would typically not be available at remote locations, increasing the benefit of the low power consumption of the copper sulphate process. A modular copper sulphate production plant that is easily transported, assembled and disassembled provides the flexibility to relocate multiple times once a deposit is depleted. The ability to move the equipment modules allows the capital cost of the plant to be amortised over multiple small mining sites, thus enabling the economic recovery of copper from small deposits. The capital and operating cost benefits of such a modular copper sulphate production plant are evaluated, and a case is presented for the use of this approach to recover copper from small and remote ore deposits.

   33. EcoMetales: Waste Management Solutions for Value Recovery and Stabilization of Deleterious Elements

       Oscar Castañeda, Ricardo Pezoa

       Abstract

       EcoMetales, a Chilean subsidiary of Codelco, is dedicated to recovering valuable metals and stabilizing harmful elements from mining waste. Located in Calama, Chile, near Codelco's Chuquicamata Smelter and Ministro Hales Roaster Plant, EcoMetales has processed over 773,000 tonnes of flue dust, recovering 137,000 tonnes of copper. Since 2013, the company has pioneered an atmospheric scorodite industrial process, successfully stabilizing nearly 25,000 tonnes of arsenic. EcoMetales is committed to addressing various challenges within Codelco's operations, including waste minimization, valuable metal recovery, and environmentally friendly arsenic removal. To support these endeavors, the company operates a well-equipped metallurgical laboratory and pilot plant. With extensive experience in processing waste from concentrator and smelting operations, EcoMetales has developed specialized expertise in value recovery and hazardous element stabilization. This paper will provide an overview of the company's work in metallurgical residue processing and highlight the innovative technologies it has developed for the mining industry.

   34. Value Recovery From Flue Dust Leaching Residue

       Ricardo Pezoa, Marcelo Acuña

       Abstract

       EcoMetales is at the forefront of developing sustainable mining processes. A key focus within the industry is the development of hydrometallurgical processes to recover valuable metals from mining residues and stabilize harmful elements. EcoMetales has pioneered an environmentally friendly solution for arsenic treatment. More recently, we've developed a novel process to recover germanium and silver from mining residues through a series of leaching steps. Our innovative approach involves the treatment of flue dust to recover copper and stabilize arsenic as scorodite. The resulting leached residue, known as “borras,” contains valuable metals including copper, lead, germanium, and silver. Through a series of acidic and alkaline leaching steps, we: recover copper and ferric sulfate which are used in our conventional scorodite production process; produce a lead concentrate which meets technical quality standards; recover germanium with a dedicated process; and obtain a silver concentrate which contains over 10% silver, with an overall recovery rate exceeding 80%. The final residue, primarily composed of aluminosilicates, can be safely disposed of in an authorized landfill. Our process has been successfully demonstrated at laboratory, bench, and pilot scales. Advanced techniques like SEM, XRD, and QEMSCAN have been employed to analyze the various fractions and products obtained. In our view, by treating mining residues and recovering valuable metals, we minimize waste generation and contribute to a more sustainable mining industry.

   35. Endolith Biodiagnostics Enables a More In-Depth Mining/Biotech Integration—Enhancing Copper Recovery from Low-Grade Sulfide Ores

       Stephan Christel, Alexander Pearson-Goulart, Tia Schumacher, Renee Hodges, Christine Green, Liz Dennett

       Abstract

       Bioleaching has been vital for copper production, enabling low-grade sulfide ore processing. While its principles are well understood, large-scale heap leaching faces challenges in optimizing microbial and operational factors. Microbial communities, essential for sulfide oxidation, are often poorly understood, leading to inefficiencies that hinder copper recovery. Sentinel Heap, Endolith’s bioheap monitoring platform, aims to integrate microbial and geochemical data to optimize leaching. Its real-time diagnostics and intuitive dashboard help operators enhance microbial leach catalysis and copper recovery. Endolith’s Biohatchery further supports operations by producing site-specific bioleaching inoculants. In this report, Endolith demonstrates the benefit of microbial community management in column leach experiments, achieving both higher Cu recovery, and higher potential for heat generation via sulfide oxidation. As ore grades decline, advanced bioleaching and data-driven optimization are crucial for sustainable copper extraction. Endolith fosters mining-biotech integration to improve efficiency and economic viability.

   36. Modoc Solvent Extraction Plant Hybrid Configuration

       Robin Jose, Mitchell Farquharson, Aron Tyab, Brandon Wellbrook

       Abstract

       Copper solvent extraction (SX) configurations are generally simple with limited extraction, strip, and wash stages. However, these configurations can vary widely between operations due to the unique pregnant leach solution (PLS) chemistry and production targets of a given operation. As some operations expand to handle higher PLS flows, grades or recovery targets, the configuration can also require changes to manage plant optimization and efficiency. This has recently been observed at one SX plant in Morenci, Arizona, which led to a unique hybrid configuration being operated in its two trains. One train has been converted from a series parallel configuration to an all-parallel configuration to manage higher flow rates and reduce entrainment. The wash stages have also been reconfigured to process a unique high copper and acid stream more effectively. Utilizing this unique stream as feed into the wash stages and conversion of the wash stages to a series configuration has allowed both washing of chemical and physical impurities along with enhancing copper recovery. This paper will discuss the plant changes at the Morenci operation and incorporation of a unique SX feed solution combined with a new hybrid SX configuration to drive plant optimization and efficient performance.

   37. Modelling Copper Leaching in Heap Systems Considering Competing Reaction Mechanisms and Coupled Dissolution with Reprecipitation (CDR) Processes

       Eric O. Ansah, Jay R. Black, Ralf R. Haese

       Abstract

       Chalcopyrite, an abundant source of copper, is noted to undergo slow dissolution under ambient conditions due to the formation of secondary minerals at the chalcopyrite surface, also referred to as surface passivation. Although the passivation mechanism has been extensively studied, the present models do not adequately account for it. This study investigates the impact of secondary mineral formation on copper extraction from chalcopyrite. A reaction pathway model (RPM) incorporating a surface passivation model (SPM) was developed to simulate the dissolution process and the formation of secondary minerals like jarosite. The study also highlights the importance of considering the role of different gangue minerals, such as hematite and gypsum, which can influence copper dissolution rates. RPM with different rate laws describing proton-promoted, ferric-iron promoted, and combined ferric-iron-proton-promoted chalcopyrite dissolution in the presence of gangue minerals in chloride system were used. The reaction mechanism that facilitated the fastest dissolution of chalcopyrite was that promoted by ferric iron. Nonetheless, the production of iron-hydroxy sulphates (like jarosite), iron oxide (hematite), and various gangue minerals inhibited the mobilisation of copper, underscoring the significance of precisely depicting primary and secondary reactions, their co-location, and their reaction behaviour. The results of this investigation are significant because they offer fresh perspectives on the simultaneous processes governing copper recovery in heaps and the most effective modelling techniques for these reactions.

   38. Chloride Leaching of Chalcopyrite: A Study on the Impact of Secondary Mineral Formation on Pore Geometry During Copper Extraction

       Eric O. Ansah, Jay R. Black, Ralf R. Haese

       Abstract

       This study investigates secondary minerals formation during copper sulphide leaching and their impact on pore geometry and copper mobilisation. Flow-through experiments and micro-CT analysis were employed to elucidate the role of secondary mineral formation, particularly jarosite, in influencing copper dissolution by clogging pore spaces and limiting access to the reactive surface of the copper sulphide. The results indicate a high surface area of a dissolving copper sulphide mineral promotes rapid dissolution, thereby reducing the availability of Fe³⁺ for jarosite precipitation. Leaching fine particles with NaCl at low flow rate enhanced copper recovery by decreasing tortuosity and prolonging solution-ore contact, though excessive fines may cause compaction without precise flow control. Acid-only leaching promoted macroporosity evolution but reduced copper yield due to proton depletion, making it suitable for ores with longer residence times or pre-treatment. Conversely, leaching under high flow rates in AlCl₃-rich lixiviant resulted in significantly fast copper dissolution from coarse particles (48.5 µmol/hr at high flow rate vs. 9.7 µmol/hr at low flow rate translating to over 90% copper recovery at high flow rate against ~25% recovery at low flow rate within 5 days), despite higher tortuosity and jarosite formation. Moderately high Eh and acidity conditions in AlCl₃-media promotes the formation of an Al-SO₄ phase, further limiting Fe³⁺ availability for jarosite formation. The formation of precipitates during copper heap leaching emphasises the need for robust drainage and solution management to mitigate channelling or flooding.

   39. Overcoming Passivation: Accelerating Copper Leaching from Low-Grade Ores and Mine Waste with AlCl3

       Eric O. Ansah, Jay R. Black, Anita Parbhakar-Fox, Ralf R. Haese

       Abstract

       The rising demand for copper in a low-carbon future necessitates efficient extraction methods. This study introduces a novel approach to copper extraction using AlCl₃ as a lixiviant. AlCl₃, a cost-effective reagent with diverse industrial applications, promotes direct and indirect dissolution mechanisms. The direct mechanism involves the formation of Al-rich precipitates, which facilitate the release of Fe³⁺ ions, a key oxidant for copper dissolution. Additionally, AlCl₃ can catalyze the transformation of chalcopyrite into more soluble secondary copper phases, such as covellite-like, via a Lewis acid mechanism. In contrast to traditional lixiviants, AlCl₃-based systems can limit the formation of passivating secondary minerals like jarosite. The formation of Al-rich precipitates, which are more soluble and porous, can hinder the formation of jarosite and maintain a higher concentration of Fe³⁺ in solution. This study provides valuable insights into the potential of AlCl₃-based leaching for efficient copper extraction from low-grade ores and mine waste as well as offers a promising alternative to conventional methods.

   40. Evaluating Seawater as a Sustainable Solution for Acid Mine Drainage Treatment

       Cleavon Wang, Zihe Ren

       Abstract

       Acid mine drainage (AMD) is characterized by low pH and high concentrations of heavy metals and sulfates and poses a significant environmental challenge for mining-impacted watersheds. Conventional treatments for AMD involve the costly addition of limestone to neutralize acidity and precipitate contaminants. This study investigates the use of seawater—a globally available, cost-effective, and sustainable resource—as an alternative treatment for AMD. By leveraging the higher pH and the content of chloride, we aim to achieve metal precipitation, pH neutralization, suppression of iron-oxidizing bacteria and reduced reactivity of sulfide minerals through environmentally compatible mechanisms. In this experiment and study, we demonstrated that the irrigation of seawater reduces the reactivity of sulfide minerals, such as pyrite, which is the culprit of AMD. It also shows that chloride concentration at seawater level (~19 g/L) or below can successfully suppress the activity of Acidithiobacillus ferrooxidans.

   41. Scanning Electron Microscopy and Reflected Light Microscopy to Investigate Chalcopyrite Leaching in the Presence of Silver

       Mitchell Catling, Ortrud Schuh, Alec Martin

       Abstract

       The silver-catalyzed leaching of chalcopyrite has been well studied and documented since Miller and Portillo (Silver catalysts in ferric sulfate leaching of chalcopyrite, pp. 691–736, 1979) published their initial findings regarding silver assisting the kinetics of chalcopyrite leaching via the formation of a silver sulfide intermediate. This study seeks to use scanning electron microscope-based energy-dispersive spectroscopy (SEM-EDS) and reflected light microscopy to investigate changing surface mineralogy as a function of leaching time when silver is present in raffinate. This involved selecting suitable mineralogy for testing, quantifying, and documenting the changes in the sample surface mineralogy pre/post-leaching and contrasting the effects of silver verses baseline as a function of leaching time. The study found that silver sulfide is present on the chalcopyrite surface during leaching, assisting in the recovery of copper from the chalcopyrite. In some cases, leaching with silver was found to deplete the surface of copper ions. This was shown by the apparent formation of various copper minerals on chalcopyrite surfaces that optically resemble covellite, digenite, and/or bornite. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) testing revealed that additional sulfur was oxidized to sulfate and was present in the leach solution at the end of the leaching period.

   42. Application of Constant Extraction Theory in Empirical Stage-Wise Estimation for Copper Solvent Extraction

       Juan Aguirre Solano, Sanja Mišković

       Abstract

       This article introduces alternative equations to undertake stage-wise analysis and numerically estimate the theoretical number of stages in extraction and stripping circuits, initially focusing on copper solvent extraction but with potential application to single or binary metal systems. These equations allow for faster, more direct calculation of efficiency, inter-stage concentrations, and stage count. The presented extraction and stripping ratio models have been developed by incorporating factors initially discarded when the Kremser equation was formulated. Hence, the constant ratio theory is followed and governs the fundamental countercurrent solvent extraction operation. Comparing the extraction–stripping models with a preliminary experimental validation, which consisted of running continuous countercurrent copper solvent extraction experiments in a mini-scale mixer-settler unit plant, it has been demonstrated that the extraction yield and stripping yield can be predicted with an accuracy of 80% to 100%. In addition, the projected stage-wise analysis for the stripping section also deviated by no more than 5% compared to the continuous Cu-solvent extraction experimental results. However, the extraction stage-wise analysis needs to be re-formulated to increase the prediction, which was around 50%.

   43. Breaking Barriers in Solvent Extraction with Miniaturized Systems: A Study of Economic and Technical Impacts

       Juan Aguirre Solano, Sanja Mišković

       Abstract

       This study explores miniaturized solvent extraction systems’ economic and technical impacts in metallurgical applications, focusing on copper and nickel recovery as preliminary study cases. By comparing a newly developed mini-scale mixer-settler unit plant with a commercial miniaturized platform and other compact mixer-settler unit setups, the research evaluates the cost-effectiveness and discusses the operational challenges for achieving a steady continuous countercurrent fashion in modular miniaturized solvent extraction (SX) setups. The copper recovery study case demonstrated that the mini-scale solvent extraction plant developed by the authors offers a cost-effective solution for R&D, with experimental costs of US$80 per test and a completion time of around 9 h. For the nickel recovery study, the projection is US$567 per test in about 25 h. Thus, larger setups required significantly higher investments. This work summarizes the key challenges in miniaturized SX systems, such as phase separation, crud formation, and scalability, which must be addressed to achieve industrial applicability. The findings suggest that while miniaturized systems promise rapid and cost-efficient R&D, further advancements are needed to overcome operational limitations and validate their use in multistage SX processes. This work underscores the potential of process intensification in metallurgical SX, offering insights into improving R&D productivity and reducing costs in metal recovery processes.

   44. Catalytic Effect of Cu(II) on the Oxidation of H2S in the Context of Leaching Chalcopyrite in Sulfuric Acidic Media

       Jordy Dinga, Jochen Petersen, Kathija Shaik, Thandazile Moyo

       Abstract

       It has been proposed in the literature that the leaching of chalcopyrite in sulfate or chloride media can occur through a combined non-oxidative/oxidative mechanism, where H₂S forms an intermediary species, and which is thought to occur concurrently with the oxidative leaching. Some studies have noted that elevated concentrations of Cu(II) improve chalcopyrite leaching in sulfate media. In this study, we investigate the role of Cu(II) in the so-called non-oxidative/oxidative process through electrochemical tests on a chalcopyrite electrode. The results are consistent with the formation of H₂S through non-oxidative leaching of chalcopyrite. The H₂S subsequently reacts with cupric ion to form intermediate cuprous sulfide species, which can be readily oxidized by dissolved oxygen. The findings support the feasibility of running heap leaching of chalcopyrite-rich ores at elevated copper concentrations in either chloride or sulfate systems.

   45. Integrated Circuit Trialling and Process Development of Metso’s Novel Mesophile-Thermophile (MesoTHERM™) Biooxidation Technology for a Primary (and Secondary) Copper Sulphide Concentrate

       C. B. van Buuren, J. A. van Niekerk, K. Haavanlammi, J. A. Strauss, M. Lampi

       Abstract

       Metso’s BIOX^® technology has been in commercial operation for over 35 years with 14 plants successfully commissioned in 11 countries. The technology has proven to be robust and effective and boasts over 36 million ounces (Oz) of gold production to date. In 2019, Metso launched its combination mesophile-thermophile biooxidation process which was aimed at reducing the cyanide consumption on conventional mesophile biooxidised residue leaching. This approach of utilising mesophiles at 40 °C for the initial extent of sulphide oxidation is quite novel as it lowers the sulphide loading and duty for the subsequent higher temperature (68–70 °C) thermophile stage, thus resulting in a less onerous mass transfer requirement at the higher thermophile temperatures. Applying the MesoTHERM approach on various base metal sulphides yielded feasible metal recoveries (>98%) for the mineral’s chalcopyrite, carrollite, and bornite. An integrated piloting trial was therefore undertaken to develop a commercial hydrometallurgical processing circuit and validate the key performance metrics of an envisioned plant flow sheet on a high-grade copper concentrate hosting primary and secondary copper sulphides and a refractory gold content. An important design feature of the trial involved the closed-loop integration of a continuous solvent extraction-electrowinning (SX-EW) piloting campaign which saw the return of raffinate to the biooxidation circuit proving that the fresh acid requirement could be largely offset. Three LME-grade copper cathodes were produced from the trial. The trial was successful and enabled the relevant understanding, circuit nuances, and process design criteria to be backed out for the design and engineering of a commercial processing facility. The trial showed that a MesoTHERM biooxidation circuit is effective to realise the oxidation of primary (notably chalcopyrite) and secondary copper sulphide minerals resulting in high metal recoveries.

   46. Metallurgical Testing of Copper, Zinc, and Cobalt Extraction from Samsun and Küre Copper Smelter Tailings via Pressure Oxidative Leaching

       C. Haslam, F. Cheuk, B. Hewitt, T. Crary, J. Brown, M. Canbazoǧlu, E. Yilmaz

       Abstract

       As the global grade of ores decline, reprocessing of tailings to recover valuable metals presents a unique opportunity to provide further economic gain from what was once considered waste. The Samsun and Küre smelters in Northern Türkiye produce waste slags that are primarily composed of fayalite (Fe₂SiO₄) but contain metals such as copper, zinc, and cobalt. To support process design and development of metals recovery from the waste tailings, experimental testwork was conducted to investigate the feasibility of pressure oxidative leaching (POL) for metal extraction. A bench scale test program established key operating conditions including feed pulp density, temperature, oxygen overpressure, sulfuric acid addition, and retention time. The co-processing pyritic concentrate as a supplemental heat/acid source was evaluated to enhance project synergies. A 96-h continuous autoclave pilot plant campaign was conducted after batch testing, achieving metal leaching extractions as high as 89% for Cu, 90% for Zn, and 96% for Co. While achieving high metal extractions, leaching of high-silicate slag tailings presented unique process challenges. POL of fayalite to liberate metals forms silica gel that can negatively impact overall leaching, acid regeneration, filterability, and material handling. This paper discusses the testwork results and engineering implications of leaching slag.

   47. Copper Recovery from Complex In Situ Leach Solutions Using Ion Exchange Resins

       Pavel Spiridonov, Leon Faulkner, Gertude Acquah, Larissa Statsenko, Egor Spiridonov, Richmond Asamoah

       Abstract

       Ion exchange resins are widely utilized to remove metals from aqueous solutions, but their limited selectivity precludes dilute ion extraction. This study seeks to support in situ valuable metal recovery techniques by investigating the adsorption performance of different commercial chelating resins, specifically Iminodiacetic acid (IDA)-type resins, toward copper. In situ leach solutions with different copper concentrations and varying impurity levels were used in this study. The results showed that IDA resins have high copper selectivity while weak acid cation resin could be used to remove iron prior to copper recovery. These findings provide an opportunity for simultaneous recovery of some of the impurities as by-product while achieving higher concentrations of the copper for efficient downstream processes.

   48. The Codelco Path to Develop Chloride Leaching for Copper Ores—Current Status

       L. María Carolina Salhe, Felipe Lagno Sánchez, Miguel Carrasco, Gerardo R. F. Alvear Flores

       Abstract

       Transforming resources into reserves is a key element that will help mining companies to meet the expected copper demand to transform modern societies. In this sense, Codelco Chile has been working in the development and implementation of a chloride leaching process to increase the production of copper unit in its northern district in the region of Calama, Chile. This paper describes the efforts done in this area with particular focus on the design, construction, and commissioning of a chloride leaching demonstration plant at Radomiro Tomic Division. The plant is expecting to start its operation on the second half of 2025.