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Recycling processes of lithium-ion batteries used in electric and hybrid vehicles are widely studied today. To perform such recycling routes, it is necessary to know the composition of these batteries and their components. In this work, three pouch and three cylindrical LIBs were discharged, dismantled, and characterized, having their compositions known and quantified. The dismantling was performed using scissors, pliers, and a precision cutter equipment. The organic liquid electrolyte was quantified via mass loss after it evaporated at 60 °C for 24 h. The separators were analyzed using Fourier-transform infrared spectroscopy (FTIR), and the cathode and anode active materials were analyzed using a scanning electronic microscope coupled to an energy-dispersive spectroscope (SEM-EDS), X-ray diffraction (XDR), and energy-dispersive X-ray fluorescence spectrometry (EDXRF). All LIBs were identified by type (NCA, NMC 442, NMC 811, LCO, and two LFP batteries), and a preliminary economic evaluation was conducted to understand their potential economic value (in USD/t). Both results (characterization and preliminary economic evaluation) were considered to discuss the perspective of recycling towards a circular economy for end-of-life LIBs. [ABSTRACT FROM AUTHOR]

Bioleaching, a process catalyzed by acidophilic microorganisms, offers a sustainable approach to metal extraction from sulfide minerals. Chalcopyrite, the world's most abundant copper sulfide, presents challenges due to surface passivation limiting its bioleaching efficiency. Also, indigenous species and microbial communities may present high copper extraction rates and offer new possibilities for application in bioleaching processes. This study examines the bioleaching potential of microbial isolates and communities obtained from Amolanas Mine in Chile. Samples were collected, cultivated, and identified by Sanger sequencing. The bioleaching potential and biofilm formation of isolates and enrichments were evaluated on pyrite and chalcopyrite. The results show the isolation of nine Leptospirillum and two Acidithiobacillus strains. The bioleaching experiments demonstrated good copper bioleaching potentials of the Leptospirillum I2CS27 strain and EICA consortium (composed mainly of Leptospirillum ferriphilum, Acidiphilium sp., and Sulfobacillus thermosulfidooxidans), with 11% and 25% copper recovery rates, respectively. Microbial attachment to the surface mineral was not mandatory for increasing the bioleaching rates. Our findings underscore the importance of indigenous microbial communities in enhancing copper bioleaching efficiency. [ABSTRACT FROM AUTHOR]

Recycling materials from end-of-life devices and products is becoming increasingly a fundamental activity for the sustainable development of nations. With the return from the market of immense quantities of photovoltaic panels at the end of their life, it is essential to foresee processes for recovering and valorizing all the raw materials present in them to avoid wasting important flows of raw materials. This research introduces a novel process aimed at the recovery of silver and silicon from end-of-life photovoltaic panels. The leaching efficiency and kinetics of ground cake powder in sulfuric acid, ferric sulfate, and thiourea were investigated in the leaching system. In particular, the influences of significant parameters, including particle size, leaching temperature, and stirring rate, on the extraction kinetics were analyzed using the shrinking core model. The results showed silver dissolving mechanisms, in which more than 90% of silver recovery at 60 min of reaction time and 99% at 120 min was achieved (120 rpm, 53–125 µm, and 40 °C). The significant effect of the leaching temperature suggests that the process is under the control of the chemical reaction. Moreover, these results were confirmed by the regression analysis of the experimental data with the shrinking core model. It can be concluded that this newly proposed process, called Gold-REC1, allows the recovery of Ag and Si (solid residue from the process) with extremely high yields and rapid kinetics. The obtained results can provide fundamental data for developing end-of-life photovoltaic recycling on an industrial scale. [ABSTRACT FROM AUTHOR]

The present paper describes the technological solution for obtaining Cu, Zn, Pb, and Ag from jarosite waste raw material, with its simultaneous separation from In and Fe. By roasting at low temperatures, iron was transformed from the Fe2(SO4)3 form into Fe2O3, which is insoluble in water and slightly soluble in acid. Copper sulfate and zinc sulfate are present in jarosite as sulfates. During temperature roasting, the copper and zinc were still in the form of CuSO4 and ZnSO4, i.e., they were easily dissolved in water. This procedure led to good selectivity of Cu and Zn compared to Fe. After water leaching, PbSO4 and Ag2SO4 remained in the solid residue. By treating jarosite with a content of 0.7% Cu, 5.39% Zn, and 5.68% Pb, products of commercial quality were obtained. By roasting jarosite in an electric furnace and leaching the roasted sample in water, leaching degrees of 91.07%, 91.97%, and 9.60% were obtained for Cu, Zn, and Fe, respectively. Using 1 M NaOH in the leaching solution, 99.93% Fe was precipitated to pH = 4. Cu in the form of CuSO4 was further treated by cementation with Zn, after which cement copper was obtained as a commercial product. Zn in the form of ZnSO4 was further treated by precipitation with Na2CO3 to obtain ZnCO3 concentrate of commercial grade. The total recovery of Pb and Ag, which were treated by chloride leaching, was 96.05% and 87.5%, respectively. The resulting NaPbCl3 solution was further treated with Na2CO3 solution, whereby PbCO3 was obtained as a commercial product. The produced PbCO3 could be further subjected to roasting to obtain soluble PbO. In these investigations, PbCO3 was smelted where a Pb anode was obtained; this was electrolytically refined to a Pb cathode. The proposed process does not pollute the environment with As and Cd. [ABSTRACT FROM AUTHOR]

In response to the problem of additive zinc concentrate consumption and inefficient reduction of ferric ion (Fe3+) in the acid-leaching solution of zinc hydrometallurgy when employing zinc sulfide concentrate, various parameters were examined. These included particle size, temperature, addition coefficient of the concentrate, and sulfuric acid concentration, all aimed at enhancing the rate of Fe3+ reduction. The results indicated that increasing the temperature from 80 to 120°C enhanced the Fe3+ reduction rate from 93.3 to 98%, reducing the time from 180 to 60 min. Furthermore, enlarging the particle size of the concentrate from below − 58/+ 48 μm to − 246/+ 150 μm, lowering the Fe3+ concentration in the reduction solution to < 0.5 g/L, and decreasing the addition coefficient from 1.8 to 1.5 further enhanced the reduction process. Additionally, employing a pressure process to increase the reduction temperature proved to be an effective strategy for enhancing the utilization rate of the zinc sulfide concentrates and the Fe3+ reduction rate, thereby reducing the amount of reduction residue and facilitating its subsequent treatment. [ABSTRACT FROM AUTHOR]

In recent years, the increasing demand and rising prices of rare earth elements (REEs), along with their attendant supply risk (about 95% of these elements are supplied by China), have led the European Commission to consider REEs as critical raw materials. Developing and optimizing processes for recovering REEs from secondary sources such as NdFeB magnets is fundamental in this context. A novel method to recover REEs by leaching with citric acid and subsequently separating these elements using the solvent extraction method has been introduced. Therefore, this research investigates the leaching efficiency of REEs, Fe, and B from NdFeB magnets. A full factorial design, with 18 experimental setups, was conducted to optimize the citric acid concentration (1–3 mol/L), leaching time (1–3 h), and solid–liquid ratio (5–10%wt./vol.). All tests were carried out at room temperature and 150 rpm. Different optimizations (response surface methodology (RSM) and artificial neural network (ANN) analysis) are used to maximize the REEs' leaching efficiency. RSM resulted in a maximum extraction yield of total rare earth elements (TREEs) of about 89% in the investigated experimental plan. This result is similar to that for ANN analysis (about 86%), but more accurate than that for RSM. In fact, for the ANN, an overall R-value higher than 0.99 was obtained. This result indicates that the developed ANN can be used as an accurate model for estimating the leaching efficiencies of REEs from NdFeB magnets. [ABSTRACT FROM AUTHOR]

The surge in mining and mineral processing to meet metal demand has led to accumulation of mining by-products like tailings, waste rocks, and acid mine drainage, containing high iron, copper, nickel, and zinc concentrations. These residues pose environmental threats. The concept of technospheric mining aims to repurpose these wastes for beneficial uses, reducing disposal and ecological impact while benefiting stakeholders. Within this context, the present investigation focuses on the discriminative retrieval of copper and nickel from mine tailings characterized by elevated iron content. This is achieved through formulation of an energy-efficient technique designed to surmount the challenge of iron co-extraction during hydrometallurgical processes aimed at extracting and recuperating metal values from intricate phases. The proposed method entails the amalgamation of mine tailings and solid NH4Cl in a stoichiometric ratio of 1:2, followed by roasting at 300 °C for a span of 1 h. Application of chloridized roasting orchestrates the transformation of copper and nickel into soluble metal chlorides, while concurrently inducing conversion of iron into a stable iron oxide state. Subsequent stages encompass the separation of copper and nickel from the water leach liquor, achieved through solvent extraction techniques utilizing LIX84I and Cyanex 272 as extractants. Rigorous characterization efforts, employing techniques such as X-ray Diffraction (XRD) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS), are undertaken to elucidate the attributes of the raw material and solid residues. Remarkably, the comprehensive isolation of copper, nickel, and iron is realized without generation of any effluents, ensuring preservation of environmental equilibrium.

The recycling of used lithium-ion batteries has become a growing concern. As a large number of rare metal elements are present in waste lithium-ion batteries, recycling them can significantly improve resource utilization and reduce the material cost of battery production. The process of recycling used lithium-ion batteries involves three main technology parts: pretreatment, material recovery, and cathode material recycling. Pretreatment includes discharge treatment, uniform crushing, and removing impurities. Material-recovery technology mainly involves traditional pyrometallurgical and hydrometallurgical technologies, as well as the developing biometallurgy technology. Analysis of existing data shows that pretreatment technology is crucial for the recycling of used lithium-ion batteries. Hydrometallurgical technology and pyro-hydrometallurgical technology are expected to be the most suitable industrialization technology paths in the future, with biometallurgical technology and direct recycling technology providing a low-pollution development direction. This article summarizes the different pretreatment techniques and valuable metal-recovery pathways. The advantages and disadvantages of each method were evaluated. The economic costs, environmental benefits, and degree of industrialization of each method were assessed. The possible development directions of various methods are summarized to provide reference for future research. [ABSTRACT FROM AUTHOR]

This review examines the technological surveillance of photovoltaic panel recycling through a bibliometric study of articles and patents. The analysis considered the number of articles and patents published per year, per country, and, in the case of patents, per applicant. This analysis revealed that panel recycling is an increasingly prominent research area. However, the number of patents filed annually has varied in recent years, averaging fewer than 200 per year. The state-of-the-art review identified three main types of treatment for photovoltaic panel recycling: mechanical, chemical, and thermal. Among these, mechanical treatment serves as a preliminary stage before the recovery of valuable elements, which is achieved through chemical or thermal processes. The articles reviewed cover a range of processes, including hydrometallurgical and pyrometallurgical methods, and explore various classification processes, solvents, and oxidizing agents. In contrast, patents predominantly focus on pyrometallurgical processes. This analysis is supplemented by a survey of market-ready technologies, many of which include stages such as size reduction or delamination followed by pyrometallurgical processes. Additionally, the review highlights the collection processes implemented by some companies, noting that the volume of panels considered waste is currently insufficient to maintain a continuous and year-round operational process. This study identifies key challenges such as (i) reducing solar panel size due to the EVA polymer complicating conventional machinery use, (ii) high process costs from the need for high temperatures and costly additives, (iii) the environmental impact of thermal treatments with high energy consumption and air pollution, and (iv) the necessity for environmentally friendly solvents in hydrometallurgical treatments to reduce contamination during recycling. Future directions include developing specific machinery for panel size reduction, either creating or modifying a polymer to replace EVA for easier treatment, adopting hydrometallurgical treatments with green solvents proven effective in recycling minerals and electronic waste, and addressing the lack of detailed information on industrial processes to make more precise recommendations. [ABSTRACT FROM AUTHOR]

The re-dissolution of unstable iron oxides during the low-temperature hematite process significantly increases the iron ions concentration in solution after iron removal in zinc hydrometallurgy. The reason for the re-dissolution of precipitated hematite was determined through simulated iron removal experiments in an autoclave. It was caused by e.g., weak acid solubility resistance in high acidity and the poor crystallinity of hematite. In order to solve the problem of re-dissolution of hematite precipitated in a short time, three improving methods, namely increasing the reaction temperature, extending the reaction time in the autoclave, and reducing the acidity of hematite process, have been systematically studied. Increasing the reaction temperature is not economical from the perspective of industrial production, and extending the reaction time does not meet the original intention of the zinc smelter to increase production capacity. Although zinc sulfide concentrate as a neutralizing agent can increase the pH of the slurry, the hematite produced does not have the potential for sales. When 12 g/L zinc calcine was added, the residual Fe concentration in solution after iron removal within 90 min can be controlled below 1 g/L, and high-grade hematite with Fe, Zn, and S contents of 56.62%, 2.09%, and 2.78% can be produced. [ABSTRACT FROM AUTHOR]

The purpose of this work is to obtain the optimum conditions for leaching the zinc contained in an industrial lead smelting slag. In this type of slag, zinc oxide, sulfide, and ferrite are contained. Zinc extraction from these compounds consists of using a single aqueous medium, where oxidant alkaline leaching with NaOH and NaClO was used. The parameters evaluated during the experiment were as follows: percentage of solids, NaOH/NaClO ratio, and temperature. The maximum amount of recovered Zn obtained during the leaching was 58%. This percentage was achieved by using the following optimal conditions: temperature of 60 °C, 0.22 of NaOH/NaClO ratio, 10% of solids, and a reaction time of 40 min. The calculated values of activation energy confirmed that the rate-limiting step of the reaction using the decreasing particle model is diffusion. The maximum percentage of zinc obtained could only have been achieved if the zinc oxide and part of the zinc sulfide (both present in almost equal proportions in the sample) were leached into the alkaline aqueous medium in the presence of NaClO. [ABSTRACT FROM AUTHOR]

The use of alumina-containing nepheline raw materials as an alternative source of alumina is relevant in the context of the limited bauxite reserves in Kazakhstan. Nepheline processing can result in products such as alumina, sodium and potassium salts, silicate products and rare metals. In terms of economic value, alumina is the most important. This article considers an advanced technology for nepheline processing for the extraction of alumina that is first purified from potassium. The application of calcium sulphate and calcium oxide as additives to the nepheline raw materials is studied. The optimal conditions for two-stage leaching with calcium additives in the form of calcium sulphate and calcium hydroxide are determined. [ABSTRACT FROM AUTHOR]

Hyperspectral imaging systems (HSIs) are becoming widespread in the mining industry for mineral classification. The spectral features detectable from near infrared to long-wave infrared make HSIs a potentially efficient tool for exploration, clay mapping, and leach pad modeling. However, the redundancy of hyperspectral data makes the analysis of hyperspectral images complicated and slow. Many researchers have proposed different algorithms and strategies to speed up processing and increase accuracy. These procedures rely on endmember extraction as one of the critical steps. However, no one has tested whether endmember extraction actually improves accuracy under all circumstances. Eliminating endmember extraction, if possible, would speed up the analysis of hyperspectral data. This study tested whether endmember extraction improves the accuracy and efficiency of mapping materials at leach pads, which are among the most complicated situations in mining environments. We compared the accuracy of abundance maps produced with fully constrained least squares (FCLS) (a) with endmember extraction by N-FINDR and (b) without endmember extraction, using a spectral library instead. The results from endmember extraction showed lower accuracy than the results from using a spectral library, probably because the spectral data were noisy and the scanned materials were mixtures. The application of FCLS to hyperspectral images provides useful information for metallurgists. The abundance maps showed that kaolinite, muscovite, and precipitation (hexahydrite and pickeringite) were the dominant minerals on the leach pad. The abundance maps of pipes and precipitation can be used to monitor leaching conditions. Lixiviant ponds mapped out in the abundance map of water can indicate saturation. This technique can also detect organic leakage and agglomeration effectiveness, but it will need different wavelength ranges and more future study. This paper also suggests best practices for using hyperspectral imaging systems to map leach pads. [ABSTRACT FROM AUTHOR]

Aluminum is produced from its primary bauxite ore through the Bayer process. Although Al is important nowadays in the development of humanity, its production leads to the generation of a huge amount of waste, called red mud. Globally, the estimation of the stock of red mud is about 4 billion tons, with about 10 million tons located in Turkey. The presence of rare-earth elements (REEs) in crucial materials such as red mud makes it a major source of these elements. A number of methods have been developed for treating red mud, which are employed globally to recover valuable products. The application of a suitable method for REE extraction from red mud is a way to overcome the supply risk, contributing to reducing the environmental issues linked to red mud pollution. The current review summarizes the research on red mud processing and examines the viability of recovering REEs from red mud sustainably, utilizing hydrometallurgy and biohydrometallurgy. [ABSTRACT FROM AUTHOR]

The usage of copper (Cu) ores containing low or no arsenic (As) has reduced, and Cu ores containing high levels of As have emerged as vital mineral resources for Cu extraction and processing. The quality of the Cu ores has decreased from 1.6% to approximately 1.0%. The proportion of As to Cu in 15% of Cu resources currently reaches 1:5. However, during the extraction and processing of Cu ores, As presents significant environmental harm. Hence, safely and effectively removing As is paramount in Cu smelting and processing, holding substantial importance in fostering environmentally sustainable practices within the Cu extraction and processing industry. This article consolidates the resource distribution of As-containing Cu (ACC) ores, comprehensively and systematically evaluates the present advancements in extracting techniques for these minerals, and identifies the challenges inherent in pyrometallurgical and wet processes for treating ACC deposits. Pyrometallurgy is a simple primary roasting technique and has widespread applicability in the treatment of various ACC minerals. Its disadvantages are the emission of exhaust gas and the high treatment costs associated with it. The wet arsenic removal method boasts advantages including minimal air pollution and a high resource recovery rate, significantly aiding in Cu concentrate recovery; its major drawback is the production of As-containing wastewater. The hydrometallurgical removal of As from ACC mines involves extracting As through leaching. Recently, biometallurgy has presented innovative solutions using specialized microorganisms to bioleach or bioabsorb As, but large-scale industrial applications still lack specific practical implementation. This review explores the underlying causes of the challenges encountered in processing ACC minerals. Additionally, it highlights pyrometallurgical roasting coupled with high-temperature filtration as a pivotal advancement in the extraction and processing of ACC ores. [ABSTRACT FROM AUTHOR]

Notable increases in metal consumption and declining ore grades in recent decades have stressed the significance of dilute solutions as secondary sources of valuable metals. Moreover, environmental considerations and the imperative of sustainable development have further emphasized their treatment. Therefore, finding an efficient solution for separating metals from dilute solutions has attracted the attention of numerous researchers. This paper reviews the purification processes of dilute solutions and highlights key achievements of published research works. Although this study focuses on evaluating the efficiency of recently developed aqueous-phase purification methods, such as immobilized ligands, ionic liquids, and air-assisted solvent extraction, the application of conventional processes to treat these solutions, such as solvent extraction, ion exchange, membranes, chemical precipitation, and adsorption are also briefly outlined. To provide a comprehensive assessment, more than 200 research articles were reviewed, and their key findings are stated in this study. This research contributes to the advancement of knowledge of metal recovery from dilute solutions and sheds light on the dynamic evolution of this field. [ABSTRACT FROM AUTHOR]

Electronic waste grows globally at a rate of 5% annually, which makes electronic waste recycling (WEEE recycling) an urgent task aimed at achieving (i) environmental protection and (ii) the preservation of mineral resources through the re-introduction of strategic metals into the market. As it turns out, WEEE recycling produces further waste, called WEEE secondary waste, which still contains valuable metals such as gold, silver, and copper. This study assessed the economic viability of recovering these metals and identified the most promising targets and approaches. WEEE secondary waste produced at a plant in southern Europe was sampled and examined for this purpose. The study methods included an ANOVA (analysis of variance) and an OCCP (orthogonal central composition plan). Over 90% gold, silver, and copper extraction was achieved with hydrochloric acid leaching in sodium hypochlorite with sodium chlorite as an oxidizing agent at 60 °C. The significance of the variation in the response for each factor, calculated using the Yates algorithm, demonstrates that by excluding sodium chloride and optimizing the doses of hydrochloric acid and sodium hypochlorite, gold can be selectively recovered through the leaching process. The scenario of HCl (2.5M)/NaClO (5%) leaching results in the maximum extraction effect of Au (91.6%) at the lowest concentrations of Ag and Cu (37–44%). [ABSTRACT FROM AUTHOR]

Among the technologies used for spent lithium-ion battery recycling, the common approaches include mechanical treatment, pyrometallurgical processing and hydrometallurgical processing. These technologies do not stand alone in a complete recycling process but are combined. The constant changes in battery materials and battery design make it a challenge for the existing recycling processes, and the need to design efficient and robust recycling processes for current and future battery materials has become a critical issue today. Therefore, this paper simplifies the current treatment technologies into three recycling routes, namely, the hot pyrometallurgical route, warm mechanical route and cold mechanical route. By using the same feedstock, the three routes are compared based on the recovery rate of the six elements (Al, Cu, C, Li, Co and Ni). The three different recycling routes represent specific application scenarios, each with their own advantages and disadvantages. In the hot pyrometallurgical route, the recovery of Co is over 98%, and the recovery of Ni is over 99%. In the warm mechanical route, the recovery of Li can reach 63%, and the recovery of graphite is 75%. In the cold mechanical route, the recovery of Cu can reach 75%, and the recovery of Al is 87%. As the chemical compositions of battery materials and various doping elements continue to change today, these three recycling routes could be combined in some way to improve the overall recycling efficiency of batteries. [ABSTRACT FROM AUTHOR]

Along with the transition to cleaner energy production methods, closing the processing loop on batteries is becoming one of the significant issues to tackle in this decade. The most promising recycling technique consists in the leaching of crushed cathode material, i.e. the dissolution of the solid battery material in an acid solution, to recover valuable metals from spent batteries. To lower process time and to use green organic solvents, ultrasonically enhanced leaching is a valid alternative to conventional processing. The mechanism of action of ultrasound during leaching is still unclear, and yet to be directly observed on solid particles. Therefore, this work aims to shed light on the underlying phenomena in the ultrasonically enhanced leaching process, by directly observing leached material. In particular, the focus is placed on the combined effect of ultrasound and acetic acid on NMC particles. Residual material from conventional and ultrasonically enhanced leaching was analyzed with inductively coupled plasma - optical emission spectrometry (ICP-OES), dynamic light scattering (DLS) and scanning electron microscopy (SEM). Conventional and ultrasonically enhanced leaching techniques were thus compared in terms of leaching efficiency, particle size distribution and morphological changes, demonstrating the beneficial effect of ultrasonic cavitation on mass transfer. Additionally, the NMC particles were exposed to ultrasound in water, to confirm that standalone ultrasonic cavitation does not lead to particles breakage. The understanding of the effect of ultrasound enables their targeted application in leaching processes and allows a deeper understanding of ultrasound in heterogeneous systems.

Heap leaching with a cyanide solution is used for processing low-grade ores; however, owing to the chemical, mineralogical, and physical characteristics of ores and their particle size distribution, extraction efficiencies are often low. This study investigated the effects of sodium acetate addition on gold extraction from Akshoky deposit ores under laboratory and semi-pilot laboratory test conditions. The gold-bearing ore used in this study had average gold and silver contents of 1.32 and 3.27 g/t, respectively. The chemical composition of the ore was as follows (wt%): copper: 0.0185, nickel: 0.0090, cobalt: 0.0025, zinc: 0.0470, lead: 0.0095, total iron: 4.10, calcium oxide: 3.08, magnesium oxide: 1.10, sodium oxide: 1.40, potassium oxide: 0.82, silicon oxide: 64.22, aluminum oxide: 13.37, arsenic: 0.023, antimony: 0.0024, total sulfur: 0.24, sulfate sulfur: 0.040, and sulfide sulfur: 0.20. Gold in the ore occurs in different forms: free/native form grains (82 %), covered with films (3.28 %), associated with sulfides (6.56 %), and in fine-grained form (8.20 %). Laboratory tests showed that gold dissolution from ground ore by a cyanide solution without sodium acetate addition was 83.08 %. However, with sodium acetate addition (0.1; 0.5; 1.0 kg/t), it increased to 84.38–86.61 %. Semi-pilot laboratory tests under heap-leaching conditions confirmed the positive effects of sodium acetate. The increase in gold extraction was 7.6 % (62.9 %) compared with that in the experiments without reagent addition (55.30 %).

The growth in the consumption of electronic products in recent years has resulted in increasing electronic device waste. At the same time, there is a decrease in the availability of raw metals required to produce electronic boards. Recycling through the recovery of precious and critical metals contained in electronic board waste is a solution, but the processes need to be safer for the environment. This paper presents the steps that lead to investment in the development of an eco-friendly and cost-effective process for recovering precious metals from end-of-life electronic telecommunications cards. Social organizations can also become involved in the recycling of electronic cards, thus enabling the integration of marginalized people into society. We examine the case of a non-profit organization whose mission is to help people living with mental health problems through the recycling of end-of-life telecommunication devices. This recycling process must operate within constraints specific to this organization and to the employment of people with mental health issues. The literature review showed that considering ecological and economic factors, the hydrometallurgical process appeared to be a logical choice. [ABSTRACT FROM AUTHOR]

Copper converter flue dust (CFD) is one of the solid wastes generated during the pyrometallurgical production of secondary copper. Due to its fine-grained character and its content of toxic heavy metals, CFD is classified as hazardous waste. CFD contains lead, zinc, and tin in the form of oxides. The aim of this paper is to design a complex hydrometallurgical process for CFD treatment in order to obtain commercially saleable products based on zinc, tin, and lead. The proposed CFD treatment process consists of leaching in acetic acid, cementation of lead from leachate by zinc, and subsequent precipitation of zinc with carbonate ions. [ABSTRACT FROM AUTHOR]

Pyrometallurgical copper production is carried out in thermal aggregates. Input waste materials with a copper content between 5% and 99% Cu are treated in the individual aggregates. In a shaft furnace, except for molten black copper, slag and shaft flue dust (SFD) are produced as waste. SFD is emitted from the melt and then is captured by fabric filters. This kind of SFD is defined as 'hazardous waste' according to the European Waste Catalogue. SFD contains an attractive quantity of valuable metals like Zn, Sn and Pb. This work focuses on the hydrometallurgical treatment of SFD from secondary copper production with the aim of obtaining usable lead-based products. [ABSTRACT FROM AUTHOR]

Nickel catalysts are widely applied in the chemical and petrochemical industry due to high catalytic activity and low cost. However, these catalysts are often irreversibly deactivated, leading to residue generation. For this reason, recycling is necessary to reduce the environmental impact of landfills and to obtain valuable metal from the secondary source. Hydrometallurgical recycling routes have been investigated to provide nickel from secondary sources. A catalyst from the petrochemical process contained 44.5% Ni and was calcined at 600°C for 3 h to remove organic compounds. Then, the material was ground, and leaching experiments were performed using H2SO4. The effects of temperature, concentration, solid-liquid ratio, particle size, and time were evaluated. The best leaching conditions were 100°C, 2 mol/L H2SO4, solid-liquid ratio 1/5, d50 8.5 µm in 8 h with 97.4% of nickel leaching (116 g/L). The leach solution was purified using chelating ion exchange resins. Three resins were studied with different functional groups: iminodiacetate, HPPA, and aminophosphonic. The effect of pH in the batch and removing contaminants in a continuous system were evaluated. Iron removal achieved 92.2% efficiency using aminophosphonic resin in a continuous process using four columns. The recovery of nickel in the process reached 94.3%. [ABSTRACT FROM AUTHOR]

In this paper, according to the reaction principle and material balance, the coefficient calculation rule is established to construct the valuable element allocation model with Java programs in the hydrometallurgy process of cobalt-rich slag. Thus, the ratio of distribution in each process containing acid leaching, copper deposition, ferromanganese precipitation, and cobalt deposition are forecast quantitatively, accompanied by the recovery rate of the valuable element. Compared with the expanding process of cobalt-rich slag, the correctness and applicability of the model for the distribution and ratio of the valuable element are investigated, and the weak link can be improved according to the specific situation of the process. The recovery rate of cobalt is 95.38 %, and the content of cobalt in the cobalt product is 44.93 % in the cobalt deposition. Ultimately, the valuable element allocation model can quantitatively predict the experimental results, indicating that it can be used for simulating and optimizing the control of the hydrometallurgy process of cobalt-rich slag. This can improve the recovery rate of valuable elements in such hydrometallurgical processes. [ABSTRACT FROM AUTHOR]

Metallic materials play a vital role in the economic life of modern societies; hence, research contributions are sought on fresh developments that enhance our understanding of the fundamental aspects of the relationships between processing, properties, and microstructures. Disciplines in the metallurgical field ranging from processing, mechanical behavior, phase transitions, microstructural evolution, and nanostructures, as well as unique metallic properties, inspire general and scholarly interest among the scientific community. Three of the most important elements are included in unit operations in non-ferrous extractive metallurgy: (1) hydrometallurgy (leaching under atmospheric and high-pressure conditions, mixing of a solution with a gas and mechanical parts, neutralization of a solution, precipitation and cementation of metals from a solution aiming at purification, and compound productions during crystallization), (2) pyrometallurgy (roasting, smelting, and refining), and (3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). Advances in our understanding of unit operations in non-ferrous extractive metallurgy are required to develop new research strategies for the treatment of primary and secondary materials and their application in industry. [ABSTRACT FROM AUTHOR]

Waste from electrical and electronic equipment exponentially increased due to the innovation and the ever-increasing demand for electronic products in our life. The quantities of electronic waste (e-waste) produced are expected to reach 44.4 million metric tons over the next five years. Consequently, the global market for electronics recycling is expected to reach $65.8 billion by 2026. However, electronic waste management in developing countries is not appropriately handled, as only 17.4% has been collected and recycled. The inadequate electronic waste treatment causes significant environmental and health issues and a systematic depletion of natural resources in secondary material recycling and extracting valuable materials. Electronic waste contains numerous valuable materials that can be recovered and reused to create renewable energy technologies to overcome the shortage of raw materials and the adverse effects of using non-renewable energy resources. Several approaches were devoted to mitigate the impact of climate change. The cooperate social responsibilities supported integrating informal collection and recycling agencies into a well-structured management program. Moreover, the emission reductions resulting from recycling and proper management systems significantly impact climate change solutions. This emission reduction will create a channel in carbon market mechanisms by trading the CO2 emission reductions. This review provides an up-to-date overview and discussion of the different categories of electronic waste, the recycling methods, and the use of high recycled value-added (HAV) materials from various e-waste components in green renewable energy technologies. [ABSTRACT FROM AUTHOR]

Multi-source ferrous metallurgical dust and sludge are significant components of iron-containing solid waste in the iron and steel industry. It is crucial for the sustainable operation of steel enterprises to recycle iron from ferrous metallurgical dust and sludge (FMDS) for use in steel smelting. However, besides Fe, FMDS also contains valuable elements such as Zn, Pb, K, and Na, among others. While these valuable elements hold high recovery value, they impede the direct reuse of FMDS by iron and steel enterprises. This paper introduces the compositional characteristics of multi-source ferrous metallurgical dust and sludge, analyzes the main recycling technologies associated with FMDS at the present stage of development, and discusses the characteristics of different technologies. In view of this, a new idea of the "cooperative treatment of multi-source ferrous metallurgical dust and sludge—full quantitative recovery of valuable elements" is put forward. This new idea integrates a variety of treatment processes to directly recycle FMDS within the steel plant, enhancing the adequacy of dust and sludge recovery and reducing the risk of environmental pollution. This paper provides a reference for achieving the full quantification and utilization of high-value-added FMDS in steel plants. [ABSTRACT FROM AUTHOR]

This paper focuses on the environmental leaching of antimony, a critical mineral, using deep eutectic solvents. Mining residues often contain embedded antimony, posing environmental risks. Deep eutectic solvents, known for being low in toxicity, cost-effective, and environmentally friendly, present a promising avenue for sustainable antimony extraction. The study focuses on optimizing the leaching process through experimental analysis by considering variables such as temperature, time, and percentage of solids. Different deep eutectic solvent (DES) compositions are being studied, including choline chloride with malonic acid, thiourea, and ethylene glycol in different molar ratios, to identify the most effective solvent system for antimony extraction. A sample, originally obtained from mining waste produced via the flotation of antimonite ore, was used to test these three types of DESs. By optimizing the leaching process by changing the ratio of solid and liquid components, as well as the amount of oxidizing agent up to 3 g, iodine, yields of up to 100% were achieved after leaching for 4 h at 100 °C. The aim of the study is to advance sustainable resource management by providing knowledge on an ecological and feasible method of extracting antimony from mine waste, leading to more conscious and efficient resource practices in the mining sector. [ABSTRACT FROM AUTHOR]

This work includes a combined hydrometallurgical treatment of a eudialyte ore sample with a subsequent preparation of leaching residue using mechanical separation methods. Hydrometallurgical treatment contains dry digestion with sulphuric acid at room temperature and filtration of the obtained product. The objectives of adopting these procedures are to test a new digestion reactor in order to prevent silica gel formation from the eudialyte ore. The obtained results revealed that silica gel formation is prevented during dissolution with sulphuric acid. A high leaching efficiency of light rare earth elements (La, Ce, Nd, Y) was reached using the dry digestion process with sulphuric acid, where the starting molarity was 12 mol/L. After the filtration process, magnetic separation is studied as the main method to recover weakly magnetic minerals like amphiboles and pyroxenes from the leaching residue in the magnetic fraction and feldspars in the nonmagnetic fraction. A new combined research strategy was developed for the production of different concentrates such as the one bearing Zr, Hf, and Nb. [ABSTRACT FROM AUTHOR]

Adopting EVs has been widely recognized as an efficient way to alleviate future climate change. Nonetheless, the large number of spent LiBs associated with EVs is becoming a huge concern from both environmental and energy perspectives. This review summarizes the three most popular LiB recycling technologies, the current LiB recycling market trend, and global recycling magnates' industrial dynamics regarding this subject. We mainly focus on reviewing hydrometallurgical and direct recycling technologies to discuss the advancement of those recycling technologies and their future commercialization pathway. [ABSTRACT FROM AUTHOR]

Recent advances in electrochemical methods promise a more sustainable recycling of rare earth elements (REEs) from discarded NdFeB permanent magnets. The demand for NdFeB magnets for clean energy applications is rapidly increasing, motivating recycling efforts to diversify REE supply. The main electrochemical steps include the selective dissolution of REE-rich phases at the anode and the reduction of REE ions at the cathode. Pretreatment with demagnetization, mechanical size reduction, and leaching contributes to the release and concentration of REEs. Thermal demagnetization and mechanical crushing make the magnets brittle and improve the penetration of leaching agents. Acid leaching dissolves the REEs, but also dissolves the iron. To facilitate the extraction of REEs at high temperatures, molten salt electrolytes such as chlorides are used, while ionic liquids allow extraction under milder conditions, but with the caveat of possible decomposition during the process. Aqueous solutions have been most thoroughly investigated due to their versatility and affordability. Fluoride-based molten salt electrolytes effectively dissolve RREs and provide a stable environment for hightemperature electrodeposition, improving the efficiency and sustainability of rare earth element recovery. To isolate highpurity REE oxides and metals, additional processing is required using techniques such as solvent extraction, selective precipitation, and electroseparation. Key factors for optimal electrochemical recycling are maximizing selectivity for REEs, minimizing energy consumption and waste generation, and simplifying integration. Although technical challenges remain, recent advances show that electrochemical technologies can improve the sustainability of recycling critical REEs from permanent magnets.

The metallurgy of lead presents significant environmental and public health challenges due to its toxicity. This is why it has been necessary to develop hydrometallurgical processes as alternatives for obtaining metal with a more sustainable and environmentally safe approach. However, these processes may involve complex chemical reactions and the use of specific chemical reagents, which may require rigorous control and monitoring to ensure the efficiency of the process and the safety of the personnel involved. In this research, the recovery of lead from a Colombian mineral with low metal content was studied by hydrometallurgical processes in carboxylic media under ambient conditions. A preliminary chemical treatment was necessary to improve the metal extraction. For this purpose, two hydrometallurgical treatments were used: i) pneumatic agitation with ozone injection and ii) mechanical agitation with hydrogen peroxide dosing. The lead extractions from the pretreated ore were similar to those from the leach without pretreatment. This situation attributed the dissolution of the lead to the complexing effect of the carboxylic agent rather than to the effect of the pretreatments. The direct addition of peroxide to the citrate leach resulted in an extraction of 50% of the metal, an improvement of more than 30% over the leach without the addition of the oxidizing agent. The leaching of the ore with 0.5M citrate and pH 4.5 yielded a redox potential of 926 mV, which ensured the high activity of the electrons in the chemical reaction and therefore the lead ions dissolution.

Leucoxene-quartz concentrate is a large-tonnage by-product of development of the Timan oil-titanium field (oil-saturated sandstones) which is not commercially used at present. High content of titanium compounds (to 50 % by weight) and lack of industrial, cost-effective, and safe technologies for its processing determine a high relevance of the work. Conventional processing technologies allow increasing the concentration of TiO2, but they are only a preparation for complex and hazardous selective chlorination. The process of pyrometallurgical conversion of leucoxene-quartz concentrate into aluminium and magnesium titanates was investigated. It was ascertained that the temperature of solid-phase reaction in Al2O3-TiO2-SiO2 system necessary for the synthesis of aluminium titanate (Al2TiO5) is 1,558 °С, and for MgO-TiO2-SiO2 system – 1,372 °С. Scaling up the process made it possible to synthesize a significant number of samples of titanate-containing products, the phase composition of which was studied by X-ray phase analysis. Two main phases were identified in the products: 30 % aluminium/magnesium titanate and 40 % silicon dioxide. In products of pyrometallurgical processing in the presence of aluminium, phases of pseudobrookite (3.5 %) and titanite (0.5 %) were also found. It was ascertained that in magnesium-containing system the formation of three magnesium titanates is possible: MgTiO3 – 25, Mg2TiO4 – 35, MgTi2O5 – 40 %. Experiments on sulphuric acid leaching of samples demonstrated a higher degree of titanium compounds extraction during sulphuric acid processing. An integrated conceptual scheme for processing leucoxene-quartz concentrate to produce a wide range of potential products (coagulants, catalysts, materials for ceramic industry) was proposed.

Lithium-ion batteries (LIBs) with high power density are commonly used in electric vehicles and portable electronic devices. Their applications have been soaring in recent years resulting in an increasing number of used LIBs. Spent LIBs containing heavy metals and toxic hazardous are becoming a severe threat to the environment and human health which must be addressed properly. Recycling is an option for end-of-life LIBs, which not only prevents the pollution of toxic components but also saves natural sources. This paper introduces battery structures and gives an overview of the current state of waste LIBs and their recycling status. Moreover, recent advancements in hydrometallurgy, pyrometallurgy, and direct recycling at both research and industrial levels are deeply analyzed. This document can serve as a useful reference resource for researchers or engineers, who might profit from applying the concept to the examples summarized in the comprehensive review paper.

This study aims to investigate the electrochemical properties of lead calcium tin (Pb–Ca(0.14%)–Sn(1.04%)) anode employed in hydrometallurgy. Various methods were employed, including cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS), to comprehensively characterize the behavior of this alloy under diverse operating conditions. The findings of this investigation indicate that the Pb–Ca(0.14%)–Sn(1.04%) anode demonstrates remarkable corrosion resistance and a lower oxygen evolution potential in comparison to conventional lead anodes. As a result, enhanced operational efficiency can be achieved. Furthermore, the incorporation of Ca and Sn in the alloy has a substantial positive effect on its mechanical properties, thereby rendering the anode more resilient in harsh operating environments. Consequently, this contributes to reduced maintenance costs. Overall, this study underscores the promising potential of lead calcium tin anodes in promoting more sustainable and efficient hydrometallurgical processes.

Bioleaching, a process catalyzed by acidophilic microorganisms, offers a sustainable approach to metal extraction from sulfide minerals. Chalcopyrite, the world’s most abundant copper sulfide, presents challenges due to surface passivation limiting its bioleaching efficiency. Also, indigenous species and microbial communities may present high copper extraction rates and offer new possibilities for application in bioleaching processes. This study examines the bioleaching potential of microbial isolates and communities obtained from Amolanas Mine in Chile. Samples were collected, cultivated, and identified by Sanger sequencing. The bioleaching potential and biofilm formation of isolates and enrichments were evaluated on pyrite and chalcopyrite. The results show the isolation of nine Leptospirillum and two Acidithiobacillus strains. The bioleaching experiments demonstrated good copper bioleaching potentials of the Leptospirillum I2CS27 strain and EICA consortium (composed mainly of Leptospirillum ferriphilum, Acidiphilium sp., and Sulfobacillus thermosulfidooxidans), with 11% and 25% copper recovery rates, respectively. Microbial attachment to the surface mineral was not mandatory for increasing the bioleaching rates. Our findings underscore the importance of indigenous microbial communities in enhancing copper bioleaching efficiency.

Recycling processes of lithium-ion batteries used in electric and hybrid vehicles are widely studied today. To perform such recycling routes, it is necessary to know the composition of these batteries and their components. In this work, three pouch and three cylindrical LIBs were discharged, dismantled, and characterized, having their compositions known and quantified. The dismantling was performed using scissors, pliers, and a precision cutter equipment. The organic liquid electrolyte was quantified via mass loss after it evaporated at 60 °C for 24 h. The separators were analyzed using Fourier-transform infrared spectroscopy (FTIR), and the cathode and anode active materials were analyzed using a scanning electronic microscope coupled to an energy-dispersive spectroscope (SEM-EDS), X-ray diffraction (XDR), and energy-dispersive X-ray fluorescence spectrometry (EDXRF). All LIBs were identified by type (NCA, NMC 442, NMC 811, LCO, and two LFP batteries), and a preliminary economic evaluation was conducted to understand their potential economic value (in USD/t). Both results (characterization and preliminary economic evaluation) were considered to discuss the perspective of recycling towards a circular economy for end-of-life LIBs.

In recent years, the increasing demand and rising prices of rare earth elements (REEs), along with their attendant supply risk (about 95% of these elements are supplied by China), have led the European Commission to consider REEs as critical raw materials. Developing and optimizing processes for recovering REEs from secondary sources such as NdFeB magnets is fundamental in this context. A novel method to recover REEs by leaching with citric acid and subsequently separating these elements using the solvent extraction method has been introduced. Therefore, this research investigates the leaching efficiency of REEs, Fe, and B from NdFeB magnets. A full factorial design, with 18 experimental setups, was conducted to optimize the citric acid concentration (1–3 mol/L), leaching time (1–3 h), and solid–liquid ratio (5–10%wt./vol.). All tests were carried out at room temperature and 150 rpm. Different optimizations (response surface methodology (RSM) and artificial neural network (ANN) analysis) are used to maximize the REEs’ leaching efficiency. RSM resulted in a maximum extraction yield of total rare earth elements (TREEs) of about 89% in the investigated experimental plan. This result is similar to that for ANN analysis (about 86%), but more accurate than that for RSM. In fact, for the ANN, an overall R-value higher than 0.99 was obtained. This result indicates that the developed ANN can be used as an accurate model for estimating the leaching efficiencies of REEs from NdFeB magnets.

The paper presents the possibility of recovering metals from printed circuit boards (PCBs) of spent mobile phones using the hydrometallurgical method. Two-stage leaching of Cu(II), Fe(III), Sn(IV), Zn(II), Ni(II) and Pb(II) with H2SO4 (2 and 5 M) and HNO3 (2 M) with the addition of H2O2 (10 and 30%) and O3 (9 or 15 g/h) was conducted at various process conditions (temperature—313, 333 and 353 K, time—60, 120, 240, 300 min, type and concentration of leaching agent, type and concentration of oxidant, solid–liquid ratio (S/L)), allowing for a high or total metals leaching rate. The use of two leaching stages allows for the preservation of selectivity, separation and recovery of metals: in the first stage of Fe(III), Sn(IV) and in the second stage of the remaining tested metal ions, i.e., Cu(II), Zn(II), Ni(II) and Pb(II). Removing Fe from the tested PCBs' material at the beginning of the process eliminates the need to use magnetic methods, the purpose of which is to separate magnetic metal particles (ferrous) from non-magnetic (non-ferrous) particles; these procedures involve high operating costs. Since the leaching of Cu(II) ions with sulfuric(VI) acid practically does not occur (less than 1%), this allows for almost complete transfer of these ions into the solution in the second stage of leaching. Moreover, to speed up the process and not generate too many waste solutions, oxidants in the form of hydrogen peroxide and ozone were used. The best degree of leaching of all tested metal ions was obtained when 2 M sulfuric(VI) acid at 353 K was used in the 1st research stage, and 2 M nitric(V) acid and 9 g/h O3 at 298 K in the 2nd stage of leaching, which allowed it to be totally leached 100% of Fe(III), Cu(II), Sn(IV), Zn(II), Ni(II) and 90% Pb(II). [ABSTRACT FROM AUTHOR]

Kenya is an East African country with the third-largest economy in sub-Saharan Africa. The demand for metals and minerals continues to increase due to urbanization, population rise, and new infrastructure growth in different countries. Kenya formally confirmed the discovery of oil and various minerals in April 2013, launching itself as a new player in Africa's rapidly expanding extractive sector. This review paper highlights the mining status in Kenya and the role of hydrometallurgical and flotation processes in the recovery of deficit metals from ores and mine wastes. The nation's 2030 Vision is anticipated to benefit greatly from the proceeds from the sale of oil, gas, and valuable metals. Because Kenya was originally mapped as an agricultural region, less mineral prospecting was done in earlier times. The country's mining industry is now dominated by the manufacture of non-metallic goods, and it is largely neglected for minerals. One of the most serious problems for the mining industry in Kenya is the production of tailings that hold strategic metals. The material is already ground, which means the most energy-consuming process has been already applied, and chemical engineering processes like leaching are more feasible at this point. Hydrometallurgical and flotation recovery of valuable metals from wastes, high and low-grade ores, or tailings is essential. The resources will be preserved, which ensures sustainability in the growth of the mining industry. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) are a widely used energy storage technology as they possess high energy density and are characterized by the reversible intercalation/deintercalation of Li ions between electrodes. The rapid development of LIBs has led to increased production efficiency and lower costs for manufacturers, resulting in a growing demand for batteries and their application across various industries, particularly in different types of vehicles. In order to meet the demand for LIBs while minimizing climate-impacting emissions, the reuse, recycling, and repurposing of LIBs is a critical step toward achieving a sustainable battery economy. This paper provides a comprehensive review of lithium-ion battery recycling, covering topics such as current recycling technologies, technological advancements, policy gaps, design strategies, funding for pilot projects, and a comprehensive strategy for battery recycling. Additionally, this paper emphasizes the challenges associated with developing LIB recycling and the opportunities arising from these challenges, such as the potential for innovation and the creation of a more sustainable and circular economy. The environmental implications of LIB recycling are also evaluated with methodologies able to provide a sustainability analysis of the selected technology. This paper aims to enhance the comprehension of these trade-offs and encourage discussion on determining the "best" recycling route when targets are in conflict. [ABSTRACT FROM AUTHOR]

To address the strong nonlinearity, uncertainty, and mutual coupling in the cobalt removal process of zinc hydrometallurgy, an algorithm based on an improved genetic algorithm (GA) backpropagation (BP) neural network combined with distributed nonlinear model predictive control (NMPC) is proposed. This method was applied to improve the quality of the purification solution and reduce the consumption of zinc powder, overcoming the challenges faced by the current cobalt removal process. First, a synergistic continuously stirred tank reactor (SCSTR) model was constructed for the dynamic cobalt removal process. Second, aiming at the problem that a single SCSTR model has difficulty describing the process accurately, based on the highly nonlinear mapping ability of data‐driven models, a method that organically integrates the SCSTR model and an error compensation model based on the GA‐BP neural network was proposed (GA‐BP‐SCSTR) to provide a more accurate online prediction of the process indicators. Then, a distributed NMPC architecture was developed using the GA‐BP‐SCSTR model, control vector parameterization (CVP) technique, and sequential quadratic programming (SQP) algorithm to achieve the coordinated control of the cobalt removal process. Finally, simulation results of an actual site showed that the prediction accuracy of the GA‐BP‐SCSTR model was higher than those of other models. The proposed predictive control method can maintain the outlet cobalt ion concentrations at the set values while achieving accurate control of the zinc powder addition. This approach can provide guidance for on‐site production and eliminate the blindness of manual experience control. [ABSTRACT FROM AUTHOR]

With the rapid development of the new energy vehicle industry, the number of power battery decommissioning is increasing year by year. The recycling of power batteries is of great significance for protecting the ecological environment, improving the efficiency of resource utilization, and ensuring the sustainable and healthy development of the new energy automobile industry. In this study, the chemical compositions of power batteries were introduced, the technical path and development status of the echelon utilization of decommissioned power batteries were discussed, and the specific steps and challenges of regenerative utilization of decommissioned power batteries were described in detail from two aspects of pyrometallurgy and hydrometallurgy. Combined with the relevant research results, the main methods of the direct regeneration of positive electrode materials were analyzed. Finally, the main development direction and related suggestions for the resource utilization of decommissioned power batteries were put forward. [ABSTRACT FROM AUTHOR]

This work focuses on the recovery of rare earth elements (REEs = La, Ce, Nd, Pr) from spent nickel–metal hydride batteries by hydrometallurgical processing. The REEs were precipitated in the form of sodium-lanthanide double sulfate salts by adding Na2SO4 to a leach liquor prepared from industrially processed spent batteries. The objectives were to better understand the parameters driving the purity of the product and to identify the phases involved, as well as their crystallographic structure. The methodology included experiments performed in a 2 L reactor, thermodynamic calculations and product characterization. We confirmed that high REE precipitation yields (>95%) can be achieved under a wide range of hydrodynamic conditions. Furthermore, we demonstrated and quantified how appropriately washing the product allows for a significant reduction in nickel losses while maintaining control over REE product purity. Finally, using X-ray Diffraction analyses, it was established that REEs form a solid solution with a chemical formula (Na0.9K0.1)(La0.65Ce0.24Pr0.04Nd0.07)(SO4)2·H2O, which has not been reported so far. [ABSTRACT FROM AUTHOR]

The expected large growth in electric mobility presents challenges, such as requiring a very large amount of critical raw materials like nickel, cobalt, and lithium. Due to this expected growth significant amounts of production scrap from cell and battery manufacturing will be generated. Over the next decade, increasingly larger amounts of Li-ion batteries from electric vehicles will also reach their end-of-life. Hence, in order to close the loop, the development and industrialization of sustainable battery recycling flowsheets are key so that both production scrap and end-of-life batteries can be recycled back to their 'battery grade' building blocks. Battery recycling flowsheets are typically categorized into two categories: (1) 'Pyro-Hydro', a combination of battery smelting in a pyrometallurgical process, followed by the further refining of the alloy via hydrometallurgy; and (2) '(Thermo)mechanical-Hydro', a combination of (thermo)mechanical pretreatment and further hydrometallurgical refining of the resulting black mass. In this paper, a carbon footprint analysis is presented comparing these two battery recycling approaches: 'Pyro-Hydro' and 'Thermomechanical-Hydro', taking into account the impact of the latest evolutions in process technology and efficiency. To facilitate this comparison, a prospective LCA was carried out for the respective flowsheets. The quantitative analysis shows that 'Pyro-Hydro' leads to the lowest overall carbon footprint but also that both 'Pyro-Hydro' and 'Thermomechanical-Hydro' flowsheets have their challenges and opportunities for decarbonization. The inclusion of the fate of side streams such as graphite and electrolyte in the analysis is shown to be critically important in order to gain an objective and complete view. [ABSTRACT FROM AUTHOR]

This study aims to investigate the electrochemical properties of lead calcium tin (Pb–Ca(0.14%)–Sn(1.04%)) anode employed in hydrometallurgy. Various methods were employed, including cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS), to comprehensively characterize the behavior of this alloy under diverse operating conditions. The findings of this investigation indicate that the Pb–Ca(0.14%)–Sn(1.04%) anode demonstrates remarkable corrosion resistance and a lower oxygen evolution potential in comparison to conventional lead anodes. As a result, enhanced operational efficiency can be achieved. Furthermore, the incorporation of Ca and Sn in the alloy has a substantial positive effect on its mechanical properties, thereby rendering the anode more resilient in harsh operating environments. Consequently, this contributes to reduced maintenance costs. Overall, this study underscores the promising potential of lead calcium tin anodes in promoting more sustainable and efficient hydrometallurgical processes. [ABSTRACT FROM AUTHOR]

Mine tailings deposits are often overlooked by the industry, posing significant environmental challenges due to chemical hazards and inadequate maintenance. Nevertheless, such mineral deposits hold considerable economic potential for processing, and the adoption of innovative technologies may also address critical chemical and physical stability issues. Existing research has demonstrated the feasibility of recovering target metals—i.e., copper, iron, manganese, cobalt, zinc, and others—through the application of acid leaching techniques with consistently high yields and metal recovery rates. Therefore, a compilation was carried out from 2008 onwards, on working conditions such as leaching agent, acid concentration, oxidizing-reducing reagent, particle size, O2 pressure, stirring speed, solid–liquid ratio, temperature, and leaching time. At present, there are no reviews on the recovery of metals via acid leaching in tailings, so this study can serve as support for future researchers who want to project themselves in this area, ordering the procedures and the results obtained by the research carried out. Regarding the evaluation, it can be commented that research has shown that acid leaching of tailings has achieved recoveries of over 90% in different metals, such as Zn, Cu, and Fe, which indicates that the treatment is efficient and recommended for different types of tailings. [ABSTRACT FROM AUTHOR]

Introduction/purpose: Bauxite residue as a waste product from the aluminium industry produced through the Bayer process is mainly composed of iron oxide, titanium oxide, silicon oxide and undissolved alumina together with a wide range of other oxides and a minor content of rare earth elements, gallium, vanadium and scandium, which vary according to the country of origin of the bauxite. The extraction of valuable elements from bauxite residues and the minimisation of bauxite residues during different treatments are an open research field. Methods: Different hydrometallurgical and pyrometallurgical methods were used for the treatment of bauxite residues. In this study, the results of the hydrometallurgical treatment of bauxite residue from Alumina Zvornik using sulfuric acid and hydrochloric acid will be shown in order to study the change of the mineralogical composition. Leaching efficiency will be calculated using the ICP OES analysis. The XRD-Analysis was used for the characterization of the initial material and solid residues studying the change of the mineralogical phases. Results: Leaching of bauxite residues with sulphuric and hydrochloric acid leads partially to the change of mineralogical structure and the transfer of elements into a liquid phase. Natural precipitation of iron is observed over time. Silica gel formation is confirmed during leaching of bauxite residues with hydrochloric acid. Conclusion: A new research strategy for treating bauxite residue is needed in order to ensure a complete change of the initial minearlogical structure and the most efficient transfer of metals into a liquid phase.

The present paper describes the technological solution for obtaining Cu, Zn, Pb, and Ag from jarosite waste raw material, with its simultaneous separation from In and Fe. By roasting at low temperatures, iron was transformed from the Fe2(SO4)3 form into Fe2O3, which is insoluble in water and slightly soluble in acid. Copper sulfate and zinc sulfate are present in jarosite as sulfates. During temperature roasting, the copper and zinc were still in the form of CuSO4 and ZnSO4, i.e., they were easily dissolved in water. This procedure led to good selectivity of Cu and Zn compared to Fe. After water leaching, PbSO4 and Ag2SO4 remained in the solid residue. By treating jarosite with a content of 0.7% Cu, 5.39% Zn, and 5.68% Pb, products of commercial quality were obtained. By roasting jarosite in an electric furnace and leaching the roasted sample in water, leaching degrees of 91.07%, 91.97%, and 9.60% were obtained for Cu, Zn, and Fe, respectively. Using 1 M NaOH in the leaching solution, 99.93% Fe was precipitated to pH = 4. Cu in the form of CuSO4 was further treated by cementation with Zn, after which cement copper was obtained as a commercial product. Zn in the form of ZnSO4 was further treated by precipitation with Na2CO3 to obtain ZnCO3 concentrate of commercial grade. The total recovery of Pb and Ag, which were treated by chloride leaching, was 96.05% and 87.5%, respectively. The resulting NaPbCl3 solution was further treated with Na2CO3 solution, whereby PbCO3 was obtained as a commercial product. The produced PbCO3 could be further subjected to roasting to obtain soluble PbO. In these investigations, PbCO3 was smelted where a Pb anode was obtained; this was electrolytically refined to a Pb cathode. The proposed process does not pollute the environment with As and Cd.