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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]

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]

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]

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]

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]

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]

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.

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]

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]

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]

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]

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]

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]

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]

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]

[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]

Exploitable or potentially exploitable deposits of critical metals, such as rare-earth (REE) and high-field-strength elements (HFSE), are commonly associated with alkaline or peralkaline igneous rocks. However, the origin, transport and concentration of these metals in peralkaline systems remains poorly understood. This study presents the results of a mineralogical and geochemical investigation of the Na-metasomatism of alkali amphiboles and clinopyroxenes from a barren peralkaline granite pluton in NE China, to assess the remobilization and redistribution of REE and HFSE during magmatic-hydrothermal evolution. Alkali amphiboles and aegirine-augites from the peralkaline granites show evolutionary trends from sodic-calcic to sodic compositions, with increasing REE and HFSE concentrations as a function of increasing Na-index [Na#, defined as molar Na/(Na+Ca) ratios]. The Na-amphiboles (i.e., arfvedsonite) and aegirine-augites can be subsequently altered, or breakdown, to form hydrothermal aegirine during late- or post-magmatic alteration. Representative compositions analyzed by in-situ LA-ICPMS show that the primary aegirine-augites have high and variable REE (2194–3627 ppm) and HFSE (4194–16,862 ppm) contents, suggesting that these critical metals can be scavenged by alkali amphiboles and aegirine-augites. Compared to the primary aegirine-augites, the presentative early replacement aegirine (Aeg-I, Na# = 0.91–0.94) has notably lower REE (1484–1972) and HFSE (4351–5621) contents. In contrast, the late hydrothermal aegirine (Aeg-II, Na# = 0.92–0.96) has significantly lower REE (317–456 ppm) and HFSE (6.44–72.2 ppm) contents. Given that the increasing Na# from aegirine-augites to hydrothermal aegirines likely resulted from Na-metasomatism, a scavenging-release model can explain the remobilization of REE and HFSE in peralkaline granitic systems. The scavenging and release of REE and HFSE by Na-metasomatism provides key insights into the genesis of globally significant REE and HFSE deposits. The high Na-index of the hydrothermal aegirine might be useful as a geochemical indicator in the exploration for these critical-metals.

The relatively high concentration of thorium and uranium in monazite poses significant environmental issues in the extraction process of rare earth elements from monazite if left untreated. A new process route that recovers both thorium and uranium as oxides has been proposed, and an analysis of its economic feasibility is presented in the current paper, based on analysis and processing of a Korean monazite sample. Comparative evaluations with existing acidic and alkaline routes have also been carried out. It was estimated that the largest proportion of the operational cost for the new process related to the materials and reagent costs. Sensitivity analysis predicted that the value of neodymium oxide followed by Heavy Rare Earth Oxides (HREO) and praseodymium oxide affect the revenue significantly. Increasing the average basket price of the total rare earths oxide by 1.5 times would result in revenues of US$158.8 million/year for the proposed route, compared to US$161.5 and US$156.3 million/year for the alkaline and acidic routes, respectively. The discounted cash flow analysis and the resulted Net Present Value (NPV) suggested that the proposed processing route was in fact the only process estimated to be economically feasible with the payback period expected to be around 4.5 years. The sale of thorium oxide and uranium oxide by-products of the proposed route contributed to the positive discounted NPV. It was also estimated that a minimum sale price of US$20/kg total rare earth oxide is required to ensure all the processes generate a positive discounted NPV. These results shown that the proposed new processing route is estimated to be economically feasible.

The global movement toward the pillars of a circular economy has restructured the entire chain of the primary production sector. Together, increases in the consumption of critical metals and in the price of high-grade mineral raw materials have encouraged the adoption of separation and treatment technologies that are adaptable to variations in the metallic values of lateritic ores deposits. Thus, this work aims to provide an overview of the conventional and potential technologies employed in the extraction and treatment processes of lateritic ores for the primary production of nickel and cobalt. Hydrometallurgical methods are predominantly used to extract target metals from laterite ores, while precipitation and solvent extraction processes are conventional separation techniques employed to concentrate the leached liquors. However, current processes are associated with high consumption of chemicals, increasing the rate of waste generation and the level of toxicity of operations. Alternative extraction routes should be explored, involving the use of combined methods to pyro-hydrometallurgy, stimulating the association of separation techniques, aiming to combine technical, economic, and environmental feasibility with the production of lateritic nickel and cobalt. Strategically, a Ni and Co recovery route was structured, based on conventional processes and including the use of alternative raw materials, such as refining by-products, to meet the demands for selective and sustainable recovery of marketable metals in the conservative and demanding industry of mining. [ABSTRACT FROM AUTHOR]

The Late Permian coal measures in eastern Yunnan, western Guizhou, and central Guangxi are significantly enriched in critical metals that could serve as important supplements to conventional critical metal deposits in China. This study collected previous geochronological and geochemical data from the Late Permian coal measures to evaluate the distribution characteristics and enrichment factors of critical metals. Moreover, metallogenic models for critical metals were also developed. The results showed that Late Permian coal measures in Yunnan, Guizhou, and Guangxi provinces exhibited abnormal enrichment in Nb, Zr, and rare earth elements (REY, or REE if Y is excluded). The Emeishan mafic rocks and intermediate-felsic volcanic ash from the Truong Son orogenic belt underwent chemical weathering, with Nb and Zr selectively preserved in situ in the form of heavy minerals (e.g., rutile, zircon, and anatase), which subsequently led to the enrichment of Nb and Zr in bauxite and Al-claystone at the bottom of the Late Permian coal measures. Intermediate-felsic volcanic ash from the Emeishan large igneous province (ELIP) and the Truong Son orogenic belt supplied Nb, Zr, and REY for the middle and upper parts of the Late Permian coal measures. The intermediate-felsic mineral material of the coal measures in the intermediate zone, outer zone, and outside zone of ELIP are derived mainly from the ELIP, the mixture from ELIP and the Truong Son orogenic belt, and the Truong Son orogenic belts, respectively. Nb, Zr, and REY were leached by acidic aqueous solutions and from the parting and roof into underlying coal seams, where they deposited as authigenic minerals or adsorbed ions on organic matter during early coalification. [ABSTRACT FROM AUTHOR]

Mantle xenoliths in a Mesoproterozoic lamprophyre dyke at Elliot Lake, Ontario, located on the east margin of the Midcontinent Rift (MCR), erupted at ~ 1.1 Ga. These xenoliths enable a study of critical metal enrichment in the sub-cratonic lithospheric mantle (SCLM). Whole-rock major and trace element data from a suite of peridotite xenoliths document a combination of melt depletion and cryptic metasomatic processes. Trace element whole-rock and mineral systematics show a specific endowment in Nb-U-REE (ca. 5–30 ppm mean value), linked to carbonated silicate metasomatism. Geochronological data from the lamprophyre host (Rb–Sr age of 1112.8 ± 4.95 Ma) and the mantle xenoliths (Re-Os) indicate that our samples document the state of the mantle during the earlier stages of magmatism of the MCR. Mineral thermobarometry reveals a hot geotherm reflecting the thinning of the Superior cratonic root to 110 km. Most of the Nb-U-REE deposits and anomalies associated with the MCR event are located around Lake Superior. Here we document for the first time north of Lake Huron, metasomatic processes in the lithosphere that may have created Nb-U-REE metal endowment. The mantle events documented here relate to other observations made in the Slave and North China craton and show how silico-carbonated mid-lithospheric metasomatism up-grades the cratonic lithospheric mantle into a fertile source. Comparison with other small degree melts such as kimberlites, and mantle metasomes related to the MARID suite, show that small degree melts are very efficient at transporting critical metals from the HFSE group plus U and Th, into Earth's lithosphere. [ABSTRACT FROM AUTHOR]

The Herberton Mineral Field hosts multiple small-scale, polymetallic Sn-Cu and Sn-Zn deposits. The Baal Gammon and Isabel polymetallic deposits in the Herberton Mineral Field contain early Sn that is overprinted by sulfides. At Baal Gammon, the sulfide overprinting is Cu-In-rich, whereas Isabel is a Zn-Pb-In-rich system. These deposits are hosted in the meta-sedimentary rocks of the Hodgkinson Formation and the porphyry dikes and volcanic rocks of the Kennedy Igneous Association. Primary Sn in these deposits occurs as cassiterite, which was altered to stannite during sulfide mineralization. The sulfide ores from Baal Gammon consist of chalcopyrite, pyrrhotite, and minor sphalerite, and sphalerite, galena, and minor chalcopyrite are observed at Isabel. Chalcopyrite from Baal Gammon contains on average 609 ppm Ag, 1194 ppm In, and 1410 ppm Sn, whereas chalcopyrite from the Isabel deposit contains on average 2302 ppm Ag, 725 ppm In, and 1042 ppm Sn. Sulfur isotope (δ34S) measurements of in-situ chalcopyrite-pyrrhotite mineral pairs show limited variation and low values that are indicative of a magmatic sulfur source with limited interaction with sulfur from connate and meteoric fluids during mineralization. The chalcopyrite and pyrrhotite δ34S values at the Baal Gammon deposit vary between 0.99–1.91‰ and 1.35–2.48‰, respectively. The δ34S values at the Isabel deposit vary between 0.91–1.45‰ for chalcopyrite and 1.12–2.11‰ for pyrrhotite. The trace element composition of major sulfides and sulfur isotopes of chalcopyrite and pyrrhotite combined with thermodynamic modeling indicates that the mineralizing fluids at the Baal Gammon and Isabel deposits have an igneous source, where the metals were transported as metal-chloride complexes at low pH (< 5) and below ~ 300 °C. The source of these sulfide-rich mineralizing fluids is most likely derived from the magmatic activity associated with the emplacement of the Slaughter Yard Creek Volcanics during a period of crustal thinning between 300 and 280 Ma. [ABSTRACT FROM AUTHOR]

At the Grimlock laterite deposit (Northern Territory, Australia), Co and Ni mineralization occurs mainly in the Mn-oxide rich layers of the ferromanganese (Fe-Mn) crust overlying ultramafic bedrock. Groundwater-associated Fe-Mn crusts consist of mineral (e.g. Mn-oxide, Fe-oxyhydroxide and silicate) groups suitable for studying triple oxygen isotopes and present unique interpretative challenges (e.g. small Mn-oxide fractions relative to Fe-Mn precipitates from other formation environments and extensive weathering). We evaluate triple oxygen isotopes within the context of changes to properties (i.e. mineralogy, major and trace element geochemistry, and degree of weathering) of a lateritic profile. We use pre-existing mineral-water fractionation factors, meteoric water δ 18O and temperature data to calculate δ 18O values of fully altered mineralogical endmembers, then, using mass balance, discuss scenarios to elucidate measured whole-rock δ 18O values. The δ ′18O (′ denotes linearized notation) and Δ ′17O of near-surface samples (0–8 m) are generally lower (mean of 8.892‰) and higher (mean of −0.141‰), respectively, than the δ ′18O (mean of 12.767‰) and Δ ′17O (mean of −0.176‰) of samples from greater depths (19–22 m). At 16–17 m depth, δ ′18O and Δ ′17O are relatively high (means of 17.509 and −0.118‰, respectively). The measured whole-rock δ 18O values are explainable by substituting lower δ ′18O values for the Mn-oxide and Fe-oxyhydroxide fractions, and higher δ ′18O values for the aluminosilicate fraction, changes coinciding with greater alteration. These results suggest that mineral weathering is primarily responsible for observed variations in the triple oxygen isotopes of groundwater-associated Fe-Mn crusts, rather than variation in the initial source of oxygen incorporated into Mn-oxide. Supplementary material: Grimlock sample photographs, XRD patterns and supplementary figures and tables are available at https://doi.org/10.6084/m9.figshare.c.7071907 [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]

In solvent extraction studies, various extractants, including TOPO, Alamine 308, TBP, TOA, LIX 84I, LIX 63, and Aliquat 336, were employed for the extraction and separation of vanadium, molybdenum, and cobalt from aqueous solutions of spent petroleum catalysts. Results indicated efficient metal recovery using these extractants. Furthermore, a combination of techniques, such as roasting, chemical or bioleaching, solvent extraction (SX), and precipitation, exhibited promising results in achieving comprehensive metal extraction and separation. Important discoveries have been made in the study of recovering important metals from wasted petroleum catalysts, especially with regard to attaining high metal recovery efficiencies. It is found that the recovery efficiency for manganese is 85%, cobalt is 87%, and nickel is 93%. Furthermore, it shows that this procedure may be carried out with high efficiency, with vanadium recovery surpassing 90% and molybdenum recovery efficiency above 95%. These outcomes signify a significant advancement in the field of metal extraction and separation, aligning with the principles of Industry 5.0 while emphasizing sustainability and efficiency in the production of high-tech materials for the modern era. [ABSTRACT FROM AUTHOR]