Hydrometallurgy最新文献

{"title":"The effect and implication of impurities on the calcination of α spodumene for lithium extraction","authors":"Mark G. Aylmore,&nbsp;Martin A. Wells,&nbsp;Zakaria Quadir,&nbsp;William D.A. Rickard,&nbsp;Kai Rankenburg,&nbsp;Brent I.A. McInnes","doi":"10.1016/j.hydromet.2025.106570","DOIUrl":"10.1016/j.hydromet.2025.106570","url":null,"abstract":"<div><div>A suite of spodumene samples from albite-spodumene type pegmatites, mined for their lithium content, in the Archaean North Pilbara and Yilgarn Cratons regions of Western Australia, were examined to assess the influence of trace element impurities in spodumene and associated gangue phases on the thermal transformation of spodumene. Calcination of spodumene is required to convert the natural, monoclinic α-spodumene form into the tetragonal β-spodumene form, which is more amenable to recovering lithium during hydrometallurgy processing.</div><div>Spodumene contains minor concentrations of Fe (500–10,000 mg/kg), Mn (200–1400 mg/kg) and other trace element impurities incorporated within the crystal structure. Primary gangue mineralogy comprises quartz, Na/K-feldspar and mica, with secondary alteration predominantly as ‘sericitic’ phyllosilicates (muscovite-lepidolite, chlorite/cookeite mixtures) variably enriched in Fe, Mn, Mg and K relative to spodumene.</div><div>Primary and secondary mica undergo thermal dehydroxylation at temperatures (&lt;950 °C) below the spodumene transformation temperature (970–1100 °C). Decomposed micas form melts that coat the surface and partially encapsulate the calcined spodumene grain surfaces. Feldspar decomposition at 1060 to 1200 °C, coincides with spodumene transformation, and can also result in melt formation, depending upon the composition of the feldspars (K-feldspar, albite). The thermal degradation of other mineral contaminants, such as biotite, pyroxene and amphibole from the presence of country rock (mafic, ultramafic) in the concentrate also coincides with the α- to β-spodumene phase transformation. The generated melts that coat grains can reduce the rate of α-β spodumene conversion and the subsequent ability to extract lithium from calcined spodumene.</div><div>Primary Fe and Mn impurities in spodumene, and those hosted by mica impurities within spodumene have a marked effect in decreasing the temperature of the α-γ-β spodumene conversion. Spodumene is not a strong conductor of heat, and the highly exothermic reaction of Fe and Mn oxidation within both mica and spodumene during thermal alteration affects thermal conductivity, leading to increased heat transfer within spodumene particles, which promotes the thermal transformation of spodumene at a lower temperature.</div><div>However, calcined spodumene particles with high Fe and Mn contents (&gt; ∼ 0.5 wt%) showed black, open sintered regions, accompanied by the generation of fine (&lt;5 μm) particles, and exsolution of Fe/Mn-oxides particles. The sintering and the generation of fines in the calciner will lead to reduced lithium recovery from calcined products.</div><div>This study illustrates the importance of minimising micaceous and feldspar components in the concentrate during the beneficiation stage, which can potentially lead to a decrease in lithium recovery during the extraction process. However, the fine-integrated nature of micas associat","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"238 ","pages":"Article 106570"},"PeriodicalIF":4.8,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144988978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of firing temperature and atmosphere on the chemical reactivity of UO2+x powders in nitric acid","authors":"Thomas Barral ,&nbsp;Laurent Claparede ,&nbsp;Nicolas Dacheux","doi":"10.1016/j.hydromet.2025.106569","DOIUrl":"10.1016/j.hydromet.2025.106569","url":null,"abstract":"<div><div>The aim of this work is to study the dissolution kinetics of a series of powdered UO_2+x samples with different structural and microstructural properties. For this purpose, UO_2+x powders were prepared by hydroxide precipitation and then heat-treated at different temperatures under argon and reducing atmospheres. The calcined UO_2+x samples were first investigated <em>ex-situ</em> by several physicochemical techniques in order to highlight the dependence of the normalized dissolution rates on various parameters. The PXRD experiments showed the preservation of the fluorite structure under reducing atmosphere over the whole temperature range studied, while the formation of a U₃O₈ phase was highlighted under argon at <em>T</em> ≤ 1100 °C. The study of the dissolution of UO_2+x samples first highlighted the effect of increasing the calcination temperature (decrease of S_SA), which significantly improves the chemical durability of the solids. The higher the calcination temperature, the lower the reactivity of the sample and the longer the time required to reach full dissolution. Secondly, the presence of a U₃O₈ fraction in some samples calcined under argon resulted in a higher normalized dissolution rate. For comparison, the normalized dissolution rate of a pure U₃O₈ sample reached <em>R</em>_<em>L</em> = (5.6 ± 1.1) × 10⁻¹ g m⁻² d⁻¹, a higher value than that of UO_2+x, <em>R</em>_<em>L</em> = 5.5 × 10⁻² g m⁻² d⁻¹ on average. Furthermore, these samples showed no change in kinetic regime during dissolution, which could be explained by the blocking by U₃O₈ of the transition to a kinetic dissolution regime autocatalyzed by nitrogen species.</div></div>","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"238 ","pages":"Article 106569"},"PeriodicalIF":4.8,"publicationDate":"2025-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144925967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extraction of Se and Te from copper anode slime through pressure oxidation, atmospheric H2SO4 leaching and reduction with sulfur dioxide and copper powder","authors":"Shuai Rao ,&nbsp;Dongxing Wang ,&nbsp;Hongyang Cao ,&nbsp;Wei Zhu ,&nbsp;Lijuan Duan ,&nbsp;Zhiqiang Liu ,&nbsp;Zhiyuan Ma","doi":"10.1016/j.hydromet.2025.106568","DOIUrl":"10.1016/j.hydromet.2025.106568","url":null,"abstract":"<div><div>Conventional H₂SO₄ pressure leaching of copper anode slime exhibits limited selenium extraction efficiency owing to the undesirable precipitation of elemental selenium. To address this challenge, this study developed an innovative sequential process combining hydrothermal phase transformation, atmospheric H₂SO₄ leaching and stepwise reduction. Thermodynamic analysis using E-pH diagrams revealed the dissolution pathways: Cu₂Se underwent stepwise transformation into soluble H₂SeO₃ via an intermediate CuSeO₃·2H₂O phase, whereas tellurium species evolved from Cu₂Te to Te(OH)₃⁺ through TeO₂ intermediates. Under optimal conditions, the integrated hydrothermal conversion-atmospheric leaching process achieved extraction efficiencies of 98.9 % Cu, 98.3 % Se, and 94.8 % Te. Subsequent recovery of selenium and tellurium from the resulting leachate employed stepwise reduction and purification, yielding final products with purities of 98.4 wt% Se and 99.1 wt% Te, respectively.</div></div>","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"238 ","pages":"Article 106568"},"PeriodicalIF":4.8,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144988979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Novel diisobutyl diamide grafted polymer resin for uranium recovery from mild nitric acid medium","authors":"Vinita Kumari ,&nbsp;Ritesh Ruhela ,&nbsp;Dhruva Kumar Singh ,&nbsp;Mahesh Tiwari ,&nbsp;Sanjay Kumar Sahu","doi":"10.1016/j.hydromet.2025.106552","DOIUrl":"10.1016/j.hydromet.2025.106552","url":null,"abstract":"<div><div>A novel diisobutyl diamide (DIBDA) grafted resin was synthesized by chemically grafting the amidic functionalities onto a commercially available styrene-divinylbenzene polymer resin. The resin was characterized using standard techniques such as FTIR, solid-state 13-C CP/MAS NMR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The sorption behavior of uranium and competing metal ions was systematically evaluated in both batch and column modes. Optimal uranium uptake was achieved from a dilute nitric acid medium at pH  2–3 in the presence of 2.0 M nitrate ions. More than 98 % uranium was stripped efficiently in a single step using 0.25 M HNO₃. Column studies using a feed containing 0.1 g/L U and a 6 mL resin bed volume yielded a strip solution with uranium concentration exceeding 1.2 g/L, corresponding to a concentration factor above 12. The resin exhibited excellent selectivity for uranium over common matrix elements such as Fe, Y, Ca, Al, and Na. Kinetic studies and sorption isotherm modelling revealed the significant role of amidic functional groups in the selective and efficient sorption of U(VI).</div></div>","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"237 ","pages":"Article 106552"},"PeriodicalIF":4.8,"publicationDate":"2025-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144893328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"X-ray tomography study on the leaching dynamics of, and pore evolution in, large chalcopyrite ore particles during chloride leaching","authors":"Luis Beiza ,&nbsp;Jochen Petersen ,&nbsp;Lilian Velásquez-Yévenes","doi":"10.1016/j.hydromet.2025.106556","DOIUrl":"10.1016/j.hydromet.2025.106556","url":null,"abstract":"<div><div>The dissolution of chalcopyrite (CuFeS₂) in a heap leaching environment is known to progress slowly; this is mainly attributed to the formation of a product layer that inhibits the dissolution of copper from the mineral. Transporting the dissolved ions from the inner regions of the larger particles to the bulk solution through cracks and/or pores might also slow the process. Therefore, a systematic long-term study has been undertaken to determine the presence and propagation of pores, fissures or crack networks in 12–17 mm particles of a sulfide ore containing mainly quartz (SiO₂), chalcopyrite and pyrite (FeS₂) during its dissolution under chloride-rich heap leaching conditions. Each particle was placed in a cylindrical receptacle and flooded with 0.1 mol/L H₂SO₄ solutions at 0, 20 and 150 g/L of chloride (as NaCl) using 0, 0.5 and 1 g/L initial cupric ion as the oxidant and leached for a period of up to 180 days at room temperature (18–22 °C). The generation of cracks and fissures and dissolution of mineral phases were observed using X-ray Computed Tomography (X-CT) at regular intervals during leaching. Additional experiments were run using 150 g/L Cl⁻ to evaluate acidity from pH -0.4 (1.0 mol/L H₂SO₄) up to pH 3, as well as the effect of temperature at room temperature and 50 °C.</div><div>The results indicated that copper dissolution increased with increasing chloride concentration at room temperature and that the initial presence of cupric ions somewhat enhances the extraction. It was found that between pH 1 and 0.2 (0.1 mol/L H₂SO₄) at 150 g/L Cl⁻ the dissolution is enhanced but inhibited at higher acid concentration. Low acidity (pH 3) promotes the precipitation of Fe that can block the pores and inhibit the dissolution of chalcopyrite. The X-CT scans confirmed that the gradual evolution of fissures and network of cracks over time enhanced the solution contact with the value mineral inside the particles, which then gradually disintegrated. In line with the leaching results, this effect seemed to be intensified at the higher chloride concentrations and when increasing temperature from 20 to 50 °C. The homogenous dissolution of chalcopyrite grains throughout the particle hints at the presence of galvanic coupling with pyrite grains as the key mode of chalcopyrite dissolution.</div></div>","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"238 ","pages":"Article 106556"},"PeriodicalIF":4.8,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144895839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sustainable copper recovery from chalcopyrite: Eutectic solvent as a green medium for leaching, in situ electrodeposition, and platform for adsorbent modification: Preliminary attempt for a zero-waste process","authors":"Ueslei G. Favero ,&nbsp;Ygor R. Guimarães ,&nbsp;Nayara T.P. Martins ,&nbsp;Nathan P. Viana ,&nbsp;Guilherme M.D. Ferreira ,&nbsp;Renê C. Silva ,&nbsp;Tiago A. Silva ,&nbsp;Maria C. Hespanhol","doi":"10.1016/j.hydromet.2025.106555","DOIUrl":"10.1016/j.hydromet.2025.106555","url":null,"abstract":"<div><div>The pyrometallurgical process for extracting copper from chalcopyrite has disadvantages related to energy consumption and pollution due to toxic gas emissions, necessitating the adoption of more sustainable approaches for copper extraction. This study proposes a circular methodology for hydrometallurgy-based leaching of chalcopyrite concentrate, using deep eutectic solvents (DES) composed of methanesulfonic acid and choline salts as green leaching agents, focusing on waste minimization. Evaluation of leaching efficiency was performed varying the anion in the choline salt (chloride, bitartrate, or dihydrogen citrate), the solid/liquid ratio (R_S-L of 0.04 and 0.02 g g⁻¹), and the DES water content (0, 10, and 30 %). After in situ copper electrodeposition directly from the leachate obtained from chalcopyrite leaching, the residue remaining was combined with an agro-industrial biomass waste to prepare a high-performance adsorbent for removing 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous media. The DES formed with choline chloride, methanesulfonic acid, and 30 % water, used at R_S-L of 0.04 g g⁻¹, enabled the leaching of 75 % of the copper from chalcopyrite. The redox behavior of the dissolved copper in the DES leachate was investigated by cyclic voltammetry, and copper was recovered by electrodeposition as metallic copper with purity of 99 %. The adsorbent exhibited a superior 2,4-D removal capacity of 170 mg g⁻¹, compared to other materials reported in the literature. The proposed process is a proof-of-concept that the use of DES can reduce the number of steps required for recovery of high-purity copper from chalcopyrite. This is a sustainable method that integrates material and energy flows, safely disposes of potentially harmful elements, and achieves zero-waste mining by applying combined circular hydrometallurgy principles.</div></div>","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"238 ","pages":"Article 106555"},"PeriodicalIF":4.8,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advancements in siderophore-based technologies for metal biorecovery","authors":"Nazanin Bahaloo-Horeh,&nbsp;Farzaneh Sadri","doi":"10.1016/j.hydromet.2025.106554","DOIUrl":"10.1016/j.hydromet.2025.106554","url":null,"abstract":"<div><div>Siderophores are low-molecular-weight, metal-chelating biometabolites that exhibit the ability to bind iron and other metal ions with high selectivity. Over 500 structurally distinct siderophores have been identified, offering diverse coordination mechanisms for potential metal complexation. Recent research has investigated their use in extracting metals from both primary and secondary sources, including ores, mine tailings, electronic waste, and industrial effluents—primarily under laboratory conditions. This review critically examines reported findings across various metal–siderophore systems, evaluating factors such as leaching parameters, synergistic use with co-lixiviants, and integration into hybrid approaches. However, no commercial applications currently exist, and significant economic and technical barriers—particularly high production costs and scalability challenges—limit practical viability. This review aims to consolidate current scientific understanding, highlight existing limitations, and outline realistic future research directions focused on overcoming technical and economic constraints to broader implementation.</div></div>","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"238 ","pages":"Article 106554"},"PeriodicalIF":4.8,"publicationDate":"2025-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144904031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An investigation into the sodium molybdate leaching of molybdenum calcine","authors":"Jiayu Mi ,&nbsp;Xingyu Chen ,&nbsp;Ailiang Chen ,&nbsp;Xuheng Liu ,&nbsp;Jiangtao Li ,&nbsp;Lihua He ,&nbsp;Fenglong Sun ,&nbsp;Zhongwei Zhao","doi":"10.1016/j.hydromet.2025.106553","DOIUrl":"10.1016/j.hydromet.2025.106553","url":null,"abstract":"<div><div>The ammonia leaching-purification-crystallization process is the conventional treatment method of molybdenum calcine. This process generates large amounts of nitrogen-containing wastewater and exhaust gases. Based on the self-coordination principle of Mo, where MoO₃ with low-polymerization ability combines with Na₂MoO₄ into highly polymerized polymolybdates, this study proposes a novel, green leaching process using Na₂MoO₄ for the selective extraction of Mo from molybdenum calcine. Leaching conditions were optimized, and the reaction mechanism was elucidated through the identification of solids using XRD, EDS mapping, XPS, and Raman spectroscopy. Results show that under optimal conditions, the leaching efficiency reached 98.6 %. Molybdenum from MoO₃, PbMoO₄, and FeMoO₄ phases in the calcine was effectively extracted, while Fe and Pb oxides remained in the leach residue as PbO and Fe₂O₃·1.2H₂O, respectively. In the leachate, Mo existed primarily as Mo₇O₂₄⁶⁻, HMo₇O₂₄⁵⁻, and MoO₄²⁻. This study presents an environmentally friendly process for extracting Mo from molybdenum calcine.</div></div>","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"237 ","pages":"Article 106553"},"PeriodicalIF":4.8,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144886127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recovery of valuable metals from spent lithium-ion batteries based on a green and efficient leaching system of dimethyl-β-propionic acid thiophene (DMPT)","authors":"Huiying Shi ,&nbsp;Yi Luo ,&nbsp;Ying Deng ,&nbsp;Jianhao Dai ,&nbsp;Jianfei Zhang ,&nbsp;Leming Ou","doi":"10.1016/j.hydromet.2025.106551","DOIUrl":"10.1016/j.hydromet.2025.106551","url":null,"abstract":"<div><div>The recycling of spent lithium-ion batteries (LIBs) represents the terminal phase of the new energy industry chain and plays a pivotal role in resource conservation and environmental protection. Despite increasing attention, the development of green and efficient recycling strategies remains a substantial challenge. In recent years, various environmentally benign solvents—including supercritical fluids, deep eutectic solvents (DES), and ionic liquids (ILs)—have been explored to promote the sustainable recycling of LIBs. Among these, the application of biomass-derived reagents (BDRs) has emerged as a promising approach due to their renewability and low environmental impact. In this study, a novel leaching strategy employing the natural organic molecule dimethyl-β-propionic acid thiophene (DMPT) is proposed for the efficient and environmentally friendly recovery of valuable metals from spent ternary LIB cathodes. Leveraging the synergistic action of carboxyl functional groups and chloride ions inherent in the DMPT structure, leaching efficiencies of Li, Ni, Co, and Mn reached 98.7 %, 97.2 %, 97.8 %, and 98.3 %, respectively. The leaching reactions and products were systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Compared with conventional hydrometallurgical processes, this DMPT-based method eliminates the need for strong acids, bases, or additional reducing agents, thus minimizing secondary pollution. The proposed approach offers a green, sustainable, and effective alternative for the recovery of critical metals from spent LIBs, and holds significant potential for future industrial application.</div></div>","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"237 ","pages":"Article 106551"},"PeriodicalIF":4.8,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144828658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of rare earth element extraction from coal byproducts using supercritical CO2","authors":"Uthej Veerla ,&nbsp;Long Fan","doi":"10.1016/j.hydromet.2025.106550","DOIUrl":"10.1016/j.hydromet.2025.106550","url":null,"abstract":"<div><div>The increasing demand for rare earth elements (REEs) in modern technologies has led to growing interest in their efficient recovery from alternative sources. Coal ash, a waste product from coal combustion, has been identified as a potential reservoir of valuable REEs, with concentrations ranging from 270 to 1480 mg/kg. This study investigates the recovery of REEs from various ranks of coal ashes using environmentally benign supercritical carbon dioxide (SC-CO₂) with tributyl phosphate (TBP) and nitric acid (HNO₃) as complexing agents. It suggests the optimal extraction conditions for potential industrial application. Experimental results indicate that sub-bituminous coal ash exhibits the highest REE recovery (60 %), followed by bituminous (48 %) and anthracite (38 %). The extraction mechanism involves three key steps: (1) dissolution of metal oxides into metal ions using HNO₃, (2) complexation of metal ions with TBP, and (3) extraction and dissolution of metal complexes in SC-CO₂. The optimum extraction conditions were determined at 60 °C, 2175 psi (15 MPa), a solid-to-chelating-agent ratio of 10:1, 120-min residence time, and TBP-HNO₃ ratio of 1:5. Under these conditions, anthracite ash achieved a recovery of 120 mg/L, bituminous ash 330 mg/L, and sub-bituminous ash 180 mg/L. The five-stage purification process that effectively purified REEs by reducing impurities such as Al, Ca, Fe, K, Mg and Mn with minimal environmental impact due to CO₂ recyclability. This research highlights supercritical fluid extraction (SCFE) as a green, scalable alternative for REEs recovery, supporting circular economy principles and offering an estimated $4.3 billion annual economic potential from U.S. coal ash.</div></div>","PeriodicalId":13193,"journal":{"name":"Hydrometallurgy","volume":"237 ","pages":"Article 106550"},"PeriodicalIF":4.8,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144781631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}