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Supplying critical metals such as cobalt, lithium, and nickel, to achieve sustainable development goals will be one of the most important concerns in the coming decades. A significant challenge in this area is the separation of some similar elements, such as nickel and cobalt. This study proposes a novel and eco-friendly process to selectively recover cobalt from nickel and manganese. The process includes two leaching stages in a microwave environment: (1) leaching by glycine to separate Ni and Mn and (2) leaching by oxalic acid to separate cobalt from other elements and precipitate it as cobalt oxalate dihydrate. In the first leaching stage, response surface methodology (RSM) was employed to optimize leaching parameters. Under the optimal conditions (3 M of glycine, 0.01 M ascorbic acid, 15 min, pH 9, 500-W microwave power, and a solid-to-liquid (S/L) ratio of 5:100), the average leaching efficiencies were 96.32% for nickel, 91.97% for manganese, and 12.11% for cobalt. In the second leaching stage, 98% of cobalt was successfully precipitated as cobalt oxalate dihydrate by oxalic acid in the microwave environment, with over 87% of the total cobalt ideally recovered from other elements. [ABSTRACT FROM AUTHOR] more...

This review emphasises the pre-treatment of waste printed circuit boards (WPCBs). Different types of pre-treatment, like physical, mechanical, chemical, and thermal processes have been discussed for analysing the extent of metal recovery from WPCBs. While most of the downstream recycling routes aim at metal recovery using specific unit processes, pre-treatment lays the foundation for enhanced material recovery. A closer and more critical examination of technological advances in the pre-treatment techniques presented in this review will strengthen the understanding of the future scope of WPCBs recycling. The study also offers insight into the material constitution of WPCBs. The advantages and disadvantages of each pre-treatment route have also been discussed. Modern recycling industries aim to combine an excellent pre-treatment process with a highly efficient material recovery process. A higher overall efficiency can be achieved with greater insight into the pre-treatment strategies. [ABSTRACT FROM AUTHOR] more...

Platinum group elements (PGEs) are commonly hosted by base metal sulfides (BMSs, e.g. chalcopyrite or pentlandite) or platinum group minerals (PGMs). PGE-bearing phases are generally small, ranging from tens of nanometres to a few micrometres. In addition, PGEs can be hosted in PGMs, either intimately associated with BMSs or spatially separated. This poses a difficulty in their detection and analysis, and leads to uncertainty in identification of their mineral hosts. Their erratic occurrence introduces a substantial nugget effect in bulk rock assays, used to evaluate deposit economics on a larger scale. Knowledge of PGE hosts has a direct influence on resource management and extraction efficiency, making the understanding of mineral distribution important for processing. The Eastman Ultramafic Intrusion is a layered mafic–ultramafic intrusive complex in the Eastern Kimberley of Western Australia. Samples from Cu–Co–Ni–PGE exploration drilling at Eastman were bulk-assayed and found to contain up to 2.39 ppm PGEs. The rocks have been strongly altered and no longer represent their primary magmatic mineral assemblage and textures. To better understand the Eastman PGE mineralogy, we applied a multi-method approach of quantitative analytical electron microscopy, 3D scanning and in situ mass spectrometry. We find that Pt is primarily hosted in sperrylite, whereas Pd is mainly associated with kotulskite, pseudomertieite, testibiopalladite, sudburyite and michenerite. Additionally, minor Pt and Pd occur in solid solution within cobaltite, as well as Rh-rich cobaltite (hollingworthite). Spatially, PGMs and cobaltite are mostly clustered on a millimetric scale, and BMSs on a micrometric scale. KEY POINTS: Three-dimensional computed tomography scanning is a valuable tool for understanding PGM distribution, nugget effect scale and narrowing down interest areas for sample analysis. Guided by 3D scanning, combined quantitative analytical electron microscopy and i mass spectrometry are effective for finding and identifying PGEs. Platinum is overwhelmingly hosted in the arsenide sperrylite, whereas palladium is mostly hosted in various bismuthides and tellurides. Cobaltite contains minor Pt and Pd. The Eastman mineralisation is primarily orthomagmatic, and later reequilibration at low temperature redistributed palladium but not platinum. [ABSTRACT FROM AUTHOR] more...

Coal gangue is a bulk industrial solid waste produced in the process of coal mining and washing, with the dual attributes of resourcefulness and hazardousness. It can be used as a reserve resource for valuable critical metals such as aluminum (Al), lithium (Li), gallium (Ga), and rare earth elements (REEs). In this paper, the occurrence modes of Li, Ga, and REEs in coal gangue were studied by sequential chemical extraction method. The extraction of valuable critical metals from the coal gangue was systematically studied by roasting activation-sulfuric acid leaching process, and the activation mechanism was elucidated. The results showed that roasting can destroy the inert kaolinite structure in coal gangue and significantly improve the leaching rate of valuable critical metals. Under the optimum conditions, the leaching rates of Al, Li, Ga, and REEs reached 86.51%, 74.46%, 95.45%, and 77.14%, respectively, and the leaching behaviors of Al, Li, and Ga were highly similar. In addition, the characterization of the leaching residue revealed 83.96% silicon oxide content with a loose and porous surface, which could be used to prepare silicon-based products. This study provides the theoretical basis and technical support for the utilization of valuable metals in coal gangue. [ABSTRACT FROM AUTHOR] more...

Rare earth elements (REEs) and cobalt (Co) are listed as critical raw materials because of their importance in global industrial production growth, high supply risk, and economic significance. The recovery of Co and REEs from secondary resources is therefore proposed as a key countermeasure to address this concern. In this study, a straightforward process that integrates acid baking and water leaching is proposed for the recovery of samarium (Sm) and Co from scrap SmCo magnets. Firstly, the chemical composition of SmCo magnets is revealed by ICP-OES and XRF. The Taguchi experimental design technique is employed to optimize nitric acid baking and water leaching. Based on the thermal decomposition behavior of Co, Fe, and Sm, the acid baking temperature is studied for the conversion of metal nitrates, excluding REEs nitrates, into metal oxides. The optimal conditions for acid baking and water leaching are identified, and a reactor for the pilot-scale acid baking process is proposed. The optimum parameters are tested with the proposed reactor. [ABSTRACT FROM AUTHOR] more...

Copyright of Nonferrous Metals (Extractive Metallurgy) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) more...

This review examines recent technological developments for recovering critical metals from mining and metallurgical waste streams, focusing on Co, Ga, Ge, In, Li, Ni, Re, Te, Sn, W, and V. Novel approaches using electrochemical methods, membranes, solvent extraction, and biomining are critically evaluated for their effectiveness and potential for industrial adoption. Key competitive advantages of these technologies are discussed, along with aspects requiring further research, such as process control, fouling issues, and microbial stability. The exploration of integrated and hybrid solutions combining different technologies is a potential game-changer for technology transfer. Finally, while these novel approaches show promise, further research is needed to overcome challenges related to cost, process control, and scalability. Addressing these issues is crucial for successfully transitioning these technologies from laboratory-scale experiments to industrial applications. By overcoming these hurdles, the mining and metallurgy sector can play a vital role in supplying critical metals for the zero-carbon transition while reducing its environmental impact and advancing toward a circular economy. [ABSTRACT FROM AUTHOR] more...

Recovery of rare earth elements from bauxite residues of lateritic versus karstic origin was explored at a pH ranging between 2.7 and 4.5 using a mixture of citric acid and citrate in water. Dissolution yields of up to 82 % for lanthanum and 62 % for yttrium were achieved with excellent selectivity toward iron (a selectivity factor of up to 4200), the main element of bauxite residues. An experimental Box-Behnken statistical design identified the concentration of citric acid/citrate and temperature as key factors controlling the dissolution yield and selectivity of rare earth elements. Observed differences in dissolution yields and selectivity as a function of origin were attributed to differences in the speciation of rare earth elements in the two bauxite residues. It is therefore possible to draw an “à la carte” graph that identified the optimum citric acid/citrate concentrations and dissolution temperatures for dissolution yields and selectivity for the two BRs. This work provides fundamental knowledge for the future development of sustainable processes for the recovery of rare earth elements from bauxite residues derived from bauxites of different origin. more...

Disruptions in the minerals supply chain play a central role in defining the future stock of minerals; therefore, an in-depth analysis of the outcomes and variables affecting exploration is required. In comparative terms, the exploration of critical minerals and major minerals presents geological and technical differences; thus, exploration budgets for critical minerals should be expected to depart from those observed in other minerals. In this context, the main goal of this paper is to contrast how exploration budgets differ between critical and major minerals when considering a set of key variables. We take a multivariate statistical analysis approach based on firm-level budget exploration data to show four key findings: exploration budgets allocated for critical minerals remain consistently lower than major minerals even when controlling for other factors. Moreover, they present a higher sensitivity to fluctuations in commodity prices. Besides, the investment made by larger companies in critical minerals significantly lags behind those made by junior companies. Additionally, the focus of exploration activity for critical minerals predominantly lies in the earlier stages of the exploration process. We expect these initial results to be used as a step forward to facilitate the discussion about exploration policies and, consequently, the reliability of the supply chain. [ABSTRACT FROM AUTHOR] more...

Critical metals such as rare earths are essential for important industrial applications and for producing high-tech materials. Currently, the development of alternative and non-conventional biomaterials has gained significant interest. This work investigated the use of crosslinked sericin-alginate-based natural polymeric particles for the removal of rare earths from water. Affinity tests showed that sericin-alginate/polyethylene glycol diglycidyl ether had the highest potential for capturing europium (0.258 mmol/g and 94.33%) and erbium (0.259 mmol/g and 94.55%). Next, erbium was selected based on the affinity with sericin-alginate/polyethylene glycol diglycidyl to investigate the effect of dose/pH, biosorption kinetics, isothermal equilibrium, desorption/reuse, and selectivity. The effect of dose and pH showed that 8.0 g/L (95.91%) and pH 5.0 (97.53%) were more efficient in capturing erbium. The biosorption kinetics showed that the equilibration time was reached within 210 min. The PSO and EMTR models effectively represented the kinetics data. The isothermal equilibrium revealed that the maximum uptake capacity for erbium was 0.641 mmol/g. The isothermal curves better fit the Dubinin-Radushkevich (55 °C) and Langmuir (25 and 40 °C) models. Thermodynamic quantitates indicated that erbium uptake was spontaneous, governed by entropic changes, and endothermic. The recovery of Er3+ was greater than 98% and the reuse of the eluent in the cycles enriched the Er3+ load 10-times (1.0 to 9.91 mmol/L). The beads also showed better performance for capturing Er3+ and Eu3+ with other coexisting ions. Characterization analyzes revealed the ion exchange mechanism between Ca2+/Er3+ prevailed in the Er3+ removal. Thus, the results pointed out that crosslinked sericin-alginate can be used as an alternative and promising biosorbent to remove and recover rare earths. [ABSTRACT FROM AUTHOR] more...

Light‐emitting diodes (LED) are widely used for energy savings. A lot of different materials and especially metals are needed to produce LED. End‐of‐life LED contain critical metals like indium or rare earth elements. In this study, first a thermochemical step is used to recover the critical metal indium from LED with hydrochloric acid‐containing vapor from polyvinyl chloride as chlorine source. Then, the LED residue is leached with sulfuric acid and hydrogen peroxide. From the leachate, the heavy rare earth element lutetium can be extracted with n‐octanol and tributyl phosphate. [ABSTRACT FROM AUTHOR] more...

The ever‐increasing importance of critical metals (CMs) in modern society underscores their resource security and circularity. Waste‐printed circuit boards (WPCBs) are particularly attractive reservoirs of CMs due to their gamut CM embedding and ubiquitous presence. However, the recovery of most CMs is out of reach from current metal‐centric recycling industries, resulting in a flood loss of refined CMs. Here, 41 types of such spent CMs are identified. To deliver a higher level of CM sustainability, this work provides an insightful overview of paradigm‐shifting pathways for CM recovery from WPCBs that have been developed in recent years. As a crucial starting entropy‐decreasing step, various strategies of metal enrichment are compared, and the deployment of artificial intelligence (AI) and hyperspectral sensing is highlighted. Then, tailored metal recycling schemes are presented for the platinum group, rare earth, and refractory metals, with emphasis on greener metallurgical methods contributing to transforming CMs into marketable products. In addition, due to the vital nexus of CMs between the environment and energy sectors, the upcycling of CMs into electro‐/photo‐chemical catalysts for green fuel synthesis is proposed to extend the recycling chain. Finally, the challenges and outlook on this all‐round upgrading of WPCB recycling are outlined. [ABSTRACT FROM AUTHOR] more...

In recent years, coal-type critical metal deposits have become a research hotspot in coal geology. As a major coal-accumulating basin in the Xinjiang area, the Turpan-Hami Basin contains abundant coal resources and has the potential to become a large coal-type critical metal deposit. However, previous studies on the enrichment characteristics of critical metal elements in coal are few and need further research. Based on SEM-EDS, XRF, and ICP-MS experiments, this study investigates the coal petrology, mineralogy, and geochemistry of the No. 22 coal of the Xishanyao Formation from the Dananhu Coal Mine, Xinjiang, to identify the sediment source, depositional environment, and controlling factors of the critical metal elements of the No. 22 coal. The results showed that the Dananhu coals are characterized by a low ash yield, low total sulfur content, high volatile yield, and high inertinite proportions. Quartz, kaolinite, and illite are the main minerals in the coal. Compared with the world's low-rank coals, Ni, Co, Mo, and Ta are slightly enriched, Li, Rb, Cs, Ba, Tl, Bi, and Ge are depleted, and the concentrations of other trace elements are comparable to the average values of the world's low-rank coals. The REY of the Dannanhu coals exhibited high fractionation, with its enrichment patterns characterized by the H-type and M-H-type. Although most of the critical metals are not enriched in the Dannanhu coals, the Ga, Zr (Hf), and Nb (Ta) concentrations in the coal ash of the Dannanhu coals have reached the economic cut-off grade and have the potential to be a substitute for rare metal resources. The terrigenous detrital sources of the Dannanhu coals mainly come from the Paleozoic dacite, andesite, and a small amount of granite from the Harik Mountain and Eastern Bogda Mountain in the Turpan-Hami Basin. The Dannanhu coals are generally in a dry and hot depositional environment, with high salinity and weak reduction-oxidation. The low source input and weak reduction-oxidation environment have resulted in low concentrations of critical metal of the No. 22 coal from the Dananhu Coal Mine. [ABSTRACT FROM AUTHOR] more...

Samarium-cobalt (SmCo) magnets, comprised of rare earth elements (REE), and cobalt (Co) are widely employed in diverse sectors such as aerospace, medical, defense, automotive, and more due to their unique properties such as outstanding high-temperature resistance, superior corrosion resistance, a higher Curie temperature, and high energy density. REE and Co are on the critical metals list for many years, along with increased production costs and challenges. With the increasing amount of waste SmCo, the recycling of these magnets has gained importance. This study investigates the recycling of SmCo magnet scraps through sulfation, selective oxidation, and water leaching. The effect of experimental parameters, such as powder/acid concentration, selective oxidation temperature, selective oxidation time, solid/liquid ratio and leaching time for water leaching are studied in detail. The optimal parameters are determined: 800°C selective oxidation temperature, 1-h selective oxidation time, 1/3 g/ml magnet: acid ratio, 2-h water leaching time and 1/20 water leaching s/l ratio. Under the optimum conditions the extraction efficiency of Sm reached approximately 65%, The solubility of Fe, Co, and Cu metals in the solution is negligible. [ABSTRACT FROM AUTHOR] more...

Rare earth elements (REE) are vital for powerful permanent magnets used in electric motors and wind turbines. These elements are chiefly sourced from carbonatites and their weathering products. The economic attractiveness of carbonatites is explained by the 10,000‐fold enrichment of REE in their mineralized portions relative to the average continental crust. Carbonatites form from mantle‐derived melts, but the ultimate origin of their REE is not completely clear. One widely cited model invokes subduction of marine sediments which accumulate REE‐rich material, priming the mantle to produce REE‐rich carbonatite melts which subsequently form deposits in the upper crust. Here we examine a global marine sediment compilation, revealing a wide variety in REE abundances and patterns. We use the sensitive lambda method that separates REE pattern curvature from redox‐related element anomalies to examine both marine sediments and presumably derived carbonatite rocks. We find that the most REE‐rich marine sediments are characterized by strongly negative Ce anomalies, which if recycled via subduction, mineralized carbonatites are expected to inherit. In contrast, we find that mineralized carbonatite rocks do not contain Ce anomalies. This indicates that the REE from the most REE‐rich marine sediments are not recycled into carbonatite deposits, and a different REE source is needed to explain carbonatite fertilities. We also find evidence that raises questions on whether any sediment‐derived REE are present in carbonatite deposits to a significant amount. We suggest that a REE‐rich source may not be required and REE enrichment occurs primarily during crustal magmatic differentiation. Plain Language Summary: Rare earth elements (REE) such as neodymium are important components of permanent magnets used in energy generation technologies including wind power turbines and electric motors. These metals are extracted from carbonatite rocks, but how the REE got to carbonatites in the first place is contentious. The seafloor contains accumulations of exceptionally REE‐rich sediments, and a popular model proposes that these REE are recycled to the mantle during subduction. Once melting occurs in the mantle, these same REE are suggested to be transported in the carbonatite melts and eventually reach the upper crust where they contribute to economic mineralization. However, the REE‐rich sediments contain a ubiquitous chemical signature in the form of a redox‐sensitive negative cerium anomaly. We show that the anomaly does not occur in carbonatite rocks, with the implication that recycled REE‐rich sediments cannot necessarily be the source for carbonatite‐related ore deposits. Key Points: Subducted REE‐rich sediments with negative Ce anomalies are thought to supply carbonatites with their REECarbonatites have no statistically significant negative Ce anomalyRecycling of particularly REE‐rich marine sediments not required for mineralization [ABSTRACT FROM AUTHOR] more...

Silicon carbide, known for its distinct chemical and physical properties, is increasingly recognized as a critical material in sectors such as energy, space, and defense. Traditional production methods like the Acheson process are energy-intensive and costly, both in terms of investment and maintenance. Additionally, the concentrated nature of its manufacturing can lead to supply bottlenecks, hindering technological progress in key areas. To address these issues, this paper proposes a circular economy approach to silicon carbide production, leveraging the ecological challenge of rice waste disposal to create a new source of silica materials. It includes an evaluation of the economic and technological feasibility of this method and introduces a multidimensional composite index to identify potential early adopters for large-scale implementation. This innovative approach not only reduces reliance on critical minerals but also offers a solution to managing agricultural waste. [ABSTRACT FROM AUTHOR] more...

[Display omitted] • Green recycling process of cathode materials from LIBs using supercritical CO 2. • scCO 2 as a green solvent for critical metal extraction at 60 °C and 250 bar. • Poly(VBPDA- co -FDA) copolymer as leaching agent, macro-ligand, and extracting agent. • H 2 O 2 and ethanol as reducing agent for Co2+ complexation in scCO 2 from LiCo(III)O 2. • Recovery yield up to 75 % of Co and Li from LiCoO 2. Supercritical CO 2 (scCO 2) extraction assisted by complexing copolymers is a promising process to recover valuable metals from lithium-ion batteries (LIBs). CO 2 , in addition to being non-toxic, abundant and non-flammable, allows an easy separation of metal-complexes from the extraction medium by depressurization, limiting the wastewater production. In this study, CO 2 -philic gradient copolymers bearing phosphonic diacid complexing groups (poly(vinylbenzylphosphonic diacid- co -1,1,2,2-tetrahydroperfluorodecylacrylate), p(VBPDA- co -FDA)) were synthesized for the extraction of lithium and cobalt from LiCoO 2 cathode material. Notably, the copolymer was able to play the triple role of leaching agent, complexing agent and surfactant. The proof of concept for leaching, complexation and extraction was achieved, using two different extraction systems. A first extraction system used aqueous hydrogen peroxide as reducing agent while it was replaced by ethanol in the second extraction system. The scCO 2 extraction conditions such as extraction time, temperature, functional copolymer concentration, and the presence of additives were optimized to improve the metals extraction from LiCoO 2 cathode material, leading to an extraction efficiency of Li and Co up to ca. 75 % at 60 °C and 250 bar. [ABSTRACT FROM AUTHOR] more...

The Xiaorequanzi deposit is a volcanic massive sulfide (VMS) deposit that occurred in Carboniferous volcano-sedimentary sequence, which is located in the western section of Dananhu-Tousuquan arc belt. East Tianshan, Critical metals such as Se are associated with Xiaorequanzi VMS deposit. However. Se occurrence status and enrichment mechanism are ambiguous, which restricts the comprehensive utilization of St. Based on previous research on the geological characteristics of ore deposits, the automated integrated mineral analysis and electron probe micro-analysis on sulfides in different mineralization stages of ore were used to explore Se occurrence status and enrichment mechanism in the Xiaorequanzi deposit. The results show that Se occurs as independent mineral. namely clausthalite, or exists in the lattice of sulfide. Clausthalite occurs in a subhedral to anhedral shape with particle size less than 30 µm. which is encapsulated in chalcopyrite of exhalative sedimentary period and late hydrothermal overprinting period. The Se, S, and Pb contents of clausthalite are 20. 25%-23.87%, 1.11%-2.61%, and 72.49% 76.57%, with an average of 22. 15%, 1.92%, and 74.51%. The average S/Se ratio is 0.087. and the average chemical formula of clausthalite is Pb (Seo. 78 S, 17). The Se contents of pyrite, chalcopyrite, and sphalerite are 0.07%, 0.15% and 0.29%, and the average S/Se ratios are 716, 222 and 110. The average content of Se and S/Se ratio of sulfide in effusive deposit period are 0.20% and 212. The average content of Se and S/Se ratio of sulfide in the late hydrothermal overprinting period are 0.05% and 938, which show a decreasing trend of Se content. Combined with the results of previous fluid inclusion studies. Se enrichment mechanism in the Xiaorequanzi deposit is attributed to the magmatic fluid with higher temperature and higher oxygen fugacity, while Se mineralization weakens followed by the decreasing of oxygen fugacity and temperature. [ABSTRACT FROM AUTHOR] more...