Rare Metal Technology 2024

The massive generation of electronic waste presents an opportunity for resource recyclingRecycling. Discarded tantalumTantalum capacitorsCapacitor contain 30–35 wt.% tantalumTantalum, which is tightly encapsulated in an epoxy housing. TantalumTantalum recyclingRecycling is necessary due to scarcity, finite resources, and geopolitical constraints. PyrolysisPyrolysis effectively degrades the epoxy resin and liberates the tantalumTantalum-rich sintered core from the outer resin. The manganese (MnO2) was removed from the core using mild acid leaching to concentrate tantalumTantalum in the leach residue. PyrolysisPyrolysis temperature (550–700 °C) influences the transformation of MnO2 to lower oxides, thereby affecting its dissolution. The decomposed epoxy housing consists mainly of silica and silver, which is subjected to density separation. The metallic enrichment in the underflow fraction is limited due to finer silver particles. Nearly, 100 g capacitorsCapacitor can yieldYield 34 g of Ta, equivalent to 0.28 tons of primary ore.

Waste printed circuit boards (WPCBs)Waste Printed Circuit Boards (WPCBs) are crucial secondary resourcesSecondary resource that contain a large number of valuable metals (Cu, Sn, Ti, Ni, Ag, Au, etc.), which have enormous recoveryRecovery value. Current methods of extractive metallurgyExtractive metallurgy have been principally focused on recovering copper and precious metals, with tin being largely overlooked. However, research has shown that the oxidation of tin to SnO(g) by H2O(g) is a viable option. This study presents a new process for selectively recovering tin from WPCBsWaste Printed Circuit Boards (WPCBs) via oxidative roasting under H2O(g) conditions. Thermodynamic analysisThermodynamic analysis was used to investigate the transformation and regulation of metallic tin to gaseous SnOSnO. It showed that tin could be highly selectively separated from WPCBsWaste Printed Circuit Boards (WPCBs). The volatilization of Sn reaches 95.2% under optimal experimental conditions. In addition, copper and noble metals were enriched in the roasted residues and could be used for copper smelting.

IndiumIndium is a strategic critical metal in manufacturing indium-tin oxide (ITO) thin films for LCD/LED screens. Nevertheless, indiumIndium in Earth’s crust is a rare dispersion with an average abundance of 0.02 ppm, which is difficult to recover from primary ore. Hence, scholars focused on Indium recoveryIndium recovery from waste LCD screensWaste LCD screen using hydrometallurgyHydrometallurgy technologies, which were always with long process. In this paper, a novel process for the separation and recoveryRecovery of indiumIndium from waste LCD by roasting under an H2-H2O atmosphere is proposed. Under optimal conditions, In2O3 can be reduced selectively to gaseous In2O, and then In2O can be recovered efficiently. The effects of roasting parameters on indium recoveryIndium recovery were studied utilizing thermodynamic analysisThermodynamic analysis, XRD, and ICP. The results showed that the indiumIndium in waste LCD can be reduced to In2O(g) under the H2-H2O atmosphere at 1100–1200 ℃, the recoveryRecovery of indiumIndium was up to 96.53% with an enrichment ratio of 3700.

The utilization of NdFeB magnetsNdFeB magnet is extensive in cutting-edge technologies such as hybrid electric vehiclesElectric vehicles and wind turbines. These magnets possess a substantial REE (Rare Earth ElementsRare earth elements) content, approximately 30%, which significantly surpasses the concentration found in natural REE ores. Due to their pronounced economic significance and the associated supply risks stemming from limited primary resources, REEs are classified as critical metals. With the NdFeB permanent magnetPermanent magnets sector experiencing an annual growth rate of 20%, the recyclingRecycling of end-of-life magnets emerges as a highly effective strategy for mitigating challenges related to the supply of essential raw materials. In the current investigation, three distinct processes have been developed to recover REEs from spent wind turbine magnets. These processes encompass (1) oxidation roasting-acid leaching, (2) chlorination roasting-water leaching, and (3) electrochemical dissolution. Optimization of process parameters has been meticulously undertaken for each of these methods to achieve the production of high-purityPurity rare earthRare earths oxide (>99%). Furthermore, a comparative evaluation has been conducted, taking into account energy efficiency and environmental sustainability, to determine the most viable approach for the sustainableSustainable recoveryRecovery of REEs from spent NdFeB magnetsNdFeB magnet.

The increasing demand for rare earth elementsRare earth elements (REEs) in renewable energy technologies and advanced materials has driven a rapid rise in both their economic importance and supply risk. Complementing the supply of REEs through recyclingRecycling of waste streams is therefore becoming increasingly significant. This study investigated the recyclingRecycling of NdFeB magnetsNdFeB magnet by separating the REEs (Pr, Nd, Sm, Dy) from impurities (Fe, Co, B) using solvent extractionSolvent extraction. The subsequent purification of REEs into individual fractions was investigated using high-performance solid phase extraction chromatographyExtraction chromatography. With solvent extractionSolvent extraction, more than 99.5% REEs could be separated in three counter-current stages using D2EHPAD2EHPA. The REEs were stripped using a 1.25 M H2SO4 solution, and finally separated into Nd and Pr, Sm, and Dy fractions from the loaded stripping solution in a single chromatographic stage using a D2EHPA-impregnated column and elution with H2SO4-gradients. This study found that the column performs well in separating any residual Fe, Co, and B impurities present in the loaded strip liquor fed to the column. The performance of the chromatographic separation is however limited by the column loading capacity at higher metal feed concentrations, where HREEs such as Dy can significantly reduce the separation efficiency of impurities and LREEs which are eluted earlier.

Rare earth elementsRare earth elements (REE) are recognized as critical raw materials because of their crucial role in vital components of numerous green and high-tech applications. In the present study, antisolventAntisolvent crystallizationCrystallization of REE sulfate hydrates of industrial interest (Nd (III), Pr (III), and Dy (III)) from sulfuric acid solutions by the addition of ethanol has been studied. CrystallizationCrystallization of REEs in the presence of Fe (II) and Fe (III) as major impurities along with Al (III), Cu (II), Co (II), and B (III) as trace elements is investigated. The incorporation of impurities and its effect on the growing REE phase is examined. The effect of controlled supersaturationSupersaturation generation rate on the product quality (e.g. purityPurity) and crystal phase is investigated. The solid phases are characterized using optical microscopy, SEM–EDX, powder-XRD, and ICP-OES. The findings can offer significant insights to understand and optimize the recoveryRecovery of REEs from leach liquor in the recyclingRecycling of magnet waste.

The need for rare earthRare earths metals in clean energy technologies such as wind turbines and electric vehiclesElectric vehicles has raised a threat to the supply and has spurred researchers to look for sourcing alternatives, with recyclingRecycling being one of the approaches. Many research investigations have demonstrated the magnet-to-metal approach, in which rare earthRare earths metals such as neodymium, praseodymium, dysprosium, and terbium, are leached from magnets by molten metals. These recycled metals can then be involved in the production of new rare earthRare earths magnets, providing an environmentally friendly source. This study provides an overview of this method of rare earthRare earths magnet recyclingMagnet recycling, which begins with demagnetization and coating removal. Leaching uses liquid magnesium and bismuth, where distillationDistillation is done by a continuous gravity-driven multiple effect thermal system (G-METS). G-METS distillationDistillation can potentially improve the efficiency of rare earthRare earths metal extraction to help establish a sustainableSustainable supply chain for rare earthRare earths magnets.

Less common metals including rare earth elementsRare earth elements (REEs), as well as Scandium (Sc), play a central role in the development of twenty-first-century economies. Common REE applications are in electronics, renewable energy, the automotive industry, defense and aerospace, medical and health care, glass and ceramics, catalysts, magnets, and metallurgy. Scandium’s main applications are in aluminum alloys, solid oxide fuel cells, and in laser technology. REEs and Sc are relatively scarce in nature, and there are a lot of efforts to extract and refine them from several primary and secondary resourcesSecondary resource such as bauxite residueBauxite Residue (BR). This paper describes the mineralogy of REEs and Sc in Greek BR. Then, it summarizes the efforts done by NTUA to extract and refine REEs and Sc either by direct leaching through H2SO4 and ion exchangeIon exchange or by direct leaching with task-specific ionic liquidsIonic liquids such as the betainium bistriflimide (HbetTf2N) and subsequent stripping with acidic HCl solutions.

Bauxite oresBauxite ore used in aluminium oxide production via the Bayer process contain trace elements (REEs, V, Li, Sc, Ga) currently not valorised. VanadiumVanadium and GalliumGallium dissolve during the Bayer process forming impurities in the Bayer liquorBayer liquor (sodium aluminate solution). VanadiumVanadium application ranges from steel to aircraft industries, and extraction involves ammonium treatment of strip liquor for vanadiumVanadium salt (AMV, V2O5) precipitation. Current crystallizationCrystallization techniques have drawbacks of generating voluminous, highly saline wastewater. This study investigated the use of antisolventAntisolvent (acetone) crystallizationCrystallization with synthetic solutions as an alternative to the crystallizationCrystallization and calcination step in the conventional production of high purityPurity vanadiumVanadium salts. The yieldYield, purityPurity, and product characteristics of the crystals for different final organic to aqueous (O/A) ratio at constant addition rate of antisolventAntisolvent at room temperature have been investigated. A batch time-dependent effect was observed with the best product quality, in terms of size and crystal habit (dominated by hexagonal laths), being attained when tb ≤ 2 h at an O/A ratio of 0.5. The early onset of acicular crystal formation and higher yieldsYield (≥ 97%), along with higher impurity incorporation into the solid phase, was observed at an O/A ratio of 0.75, and this was attributed to higher levels of supersaturationSupersaturation.

In recyclingRecycling, the separation of rare earth elementsRare earth elements (REE) from late transition metalsLate Transition Metal (LTM) represents a principal challenge. While iron can easily be separated by controlled increase in pH, separation of Co, Ni, and Cu requires application of advanced approaches including fractional crystallizationCrystallization, solvent extractionSolvent extraction, or use of solid adsorbents. The latter can be made selective by grafting of specific ligands reacting in a different manner with targeted classes of metal cations. Applying molecular modelMolecular models approach combined with advanced spectroscopic measurements, we were able to visualize principally different reaction pathways between REE and LTM in uptake by poly-amino ligands. The observed differences permit to tailor adsorbents with pronounced selectivitySelectivity on both adsorptionAdsorption and desorption of cations of interest.

Rare earth elementsRare earth elements (REE) have emerged as a hot topic of discussion in the literature. The reason for increasing interest is the usage of these elements playing a key role in especially green technology. With the increasing REE demand, the search for an alternative, and environmentally friendly extraction method is increasing day by day. At this point, it is seen that the concept of solvometallurgySolvometallurgy has attracted a considerable attention as an alternative method to traditional extraction methods. In this research, REE in Eskisehir-Beylikova Bastnasite ore is investigated using solvometallurgical methods. In the first step of the study, the ore is characterized. After the characterization, calcination was applied at different times, temperatures, and grain size configurations. The calcination experiments were designed, and conducted based on response surface experimental design. REE extraction efficiency was determined as a response, and temperature, time, particle size were identified as experimental parameters. According to results obtained from this design, temperature was found to be the most critical parameter, and calcination at 500, 600, and 700 °C was conducted to find the highest efficient experimental parameters. The experiment conducted at 500 °C yielded the highest extraction efficiency value with light REE solvoleach efficiency as 73.773 wt% while Ce leaching value was found to be 86.648 wt%. It is well understood that the ore can be leached successfully with a newly developed extraction method, solvometallurgySolvometallurgy.

(NH4)2CO3(NH4)2CO3 leaching method is an efficient and green selective vanadium extractionVanadium extraction method. Studying its leaching kineticLeaching kinetics mechanism can improve the adaptability and industrial production of this method and further promote the development of green extraction of vanadiumVanadium resources. This work used different leaching temperatures to study the variation of vanadiumVanadium leaching efficiency with leaching time to elucidate the leaching kineticsLeaching kinetics of vanadiumVanadium. Results showed that the leaching process consists of two stages and both of which complied with shrinking core model (SCM). The apparent activation energies (Ea) of leaching process were 8.80 kJ/mol (0–15 min) and 9.68 kJ/mol (15–70 min), respectively. The leaching rate in 0–15 min was controlled by solid product layer diffusion, and the leaching rate in 15–70 min was controlled by solid product layer diffusion and chemical reactions, and diffusion control played a significant role.

This study aims to develop a direct recyclingRecycling process of spent lithiumLithium-ion batteries (LIBs) from an electric vehicleElectric vehicles. In this direct recyclingRecycling process, the electric vehicleElectric vehicles battery pack is first discharged and disassembled to obtain the spent cathode material, which is then hydrothermally relithiated at 220 °C for 2 h followed by sinteringSintering at 850 °C for 4 h in air. The product after these steps is the regenerated cathode material, which is used to fabricate new LIBs to evaluate the electrochemical performance. The regenerated cathode material delivers an initial discharge capacity of 151 mAh g−1 at 0.33C (50 mA g−1) with a capacity retention of 91% after 50 cycles. By combining hydrothermal relithiationHydrothermal relithiation with sinteringSintering, lithiumLithium deficiency, structural defects, and electrochemical activity of the spent cathode material are successfully restored.

RecyclingRecycling of cathode material of spent lithiumLithium-ion batteries (LIBs) is important for recovering critical metals and protecting the environment. This study thus proposes a sustainableSustainable recyclingRecycling process for cathode material (nickelNickel-cobaltCobalt-manganese/NCM chemistry)NCM chemistry via leaching with an acidic organophosphorus extractant, di-(2-ethylhexyl)phosphoric acid/D2EHPAD2EHPA and copper (current collector) as the reducing agent. The effects of leaching parameters, including stirring speed, Cu amount, D2EHPAD2EHPA concentration, temperature, and time were investigated. The leached metals on the loaded D2EHPAD2EHPA were recovered via stripping using pH-controlled aqueous solutions. Using D2EHPAD2EHPA for leaching allows process intensification because it integrates leaching and solvent extractionSolvent extraction (SX) in one-stage operation. It also reduces the consumption of aqueous solutions, thereby minimizing wastewater generation.

The growing commitment to green energy technologies coupled with the rising usage of portable electronic devices has caused a rapid increase in lithiumLithium market demand. Currently, in the USA brines are the primary source for lithiumLithium due to their utilization of cheap and inexpensive processes; however, long lead times and low extraction yieldsYield raise concerns for potential supply chain disruptions. In this work, we examine a novel mechanochemical process for rapid lithium extractionLithium extraction from lithiumLithium-rich spodumene ore. We demonstrate multiple mechanochemically assisted ion-exchange reactions between α-spodumeneΑ-Spodumene and various solid leaching agents resulting in lithium extractionLithium extraction yieldsYield of up to 40 or 77% without or with a secondary dilute hydrochloric acid leach, respectively. Furthermore, we propose mechanisms for this enhanced lithium extractionLithium extraction from α-spodumeneΑ-Spodumene both with and without a secondary acid leach.

In a study focusing on alternate energy-efficient approaches to recover lithium from LCT pegmatites, we demonstrated that single-stage decomposition of α-spodumene in caustic media can be achieved below 450 °C without the conventional pretreatment at temperatures exceeding 1000 °C, typically required to induce a phase transition to the more reactive β-form (Gamage McEvoy et al. in Energy technology 2023, TMS Springer, pp 81–87, 2023). Considering the challenges in characterizing and monitoring the evolution of lithium, an experimental phase stability study using synthetic sodium aluminosilicates analogues along the NaAlO2-SiO2 join (e.g. carnegieite: NaAlSiO4) exposed to melted KOH was undertaken. The findings will be discussed in the context of optimizing the extent of alkali exchange and effective partitioning of silica and alumina in the solid residue that has implications for achieving selective lithium recovery in the pregnant leach solution.

To address an ongoing need for environmentally benign approaches for extracting rare earth elementsRare earth elements (REEs) from ores and secondary sources, we present a novel biosorptionBiosorption method for separating REEs from dilute aqueous solutions using bacteriophageBacteriophage. Our approach involves the genetic engineering of the major coat protein pVIII of the M13 bacteriophageBacteriophage (phage) with the lanmodulin mimetic peptideLanmodulin mimetic peptide, which binds REEs. We present results demonstrating the ability of the modified bacteriophageBacteriophage to extract REEs from dilute aqueous chloride solutions (on the order of μM concentrations) buffered by sodium acetate at pH 5, the structural changes of the pVIII protein, and the aggregation of the engineered phage induced by the REE uptake. We also report on the ability to desorb REE from the phage by pH modulation and demonstrate the recyclability of phage. Finally, we discuss how phage-based biosorptionBiosorption might be scaled up for commercial application.

Soaring demands for rechargeable Li-ion batteries in portable electronics and electric vehiclesElectric vehicles drive the unprecedented increase in post-consumer waste generation. Additionally, to fill the gaps between supply and demand for the critical elements in electrode materials, the recyclingRecycling of waste batteries has become essential. Traditional recyclingRecycling using high-energy smelting and high-reagent leaching processes generates harmful waste, hence, a new biotechnological process is being searched as a green alternative. Therefore, this study discloses a bioleaching option of LiCoO2 cathode powder using fungi, Aspergillus niger as the source of metabolic excreted organic acids lixiviant. The results of one-step bioleaching yielded 96% (w/w) lithiumLithium, whereas this efficiency was ~ 94% (w/w) with two-step bioleaching of cathode powder fed at a pulp density of 5% (w/v). The efficiency of cobaltCobalt in both types of fungal bioleaching was below 1% (w/w). Thus, the study demonstrates the potential of Aspergillus niger in lithium extractionLithium extraction from cathode powder of the battery waste, and the results will further be utilized to improve the design of bioleaching protocols for environmentally friendly recoveryRecovery of both metals from LiCoO2 powder.

PlatinumPlatinum Group Metals (PGMs) comprising platinumPlatinum, palladiumPalladium, and rhodium are rare and they are naturally occurring precious metals. They are often used in electronic components and cell phones as capacitorsCapacitor, and catalytic converters found in fuel-consuming vehicles typically contain platinumPlatinum additives to help treat exhaust fumes. In this research, platinumPlatinum and palladiumPalladium were extracted from gold plant effluentEffluent solution by adsorptionAdsorption using biobased materials. Data analysis revealed that 97.4% platinumPlatinum and 99.8% palladiumPalladium were extracted with modified bioadsorbents and the adsorptionAdsorption rate of PGMsPGM progressed via the pseudo-second-order rate model. AdsorptionAdsorption isotherm model studies indicated that the adsorptionAdsorption of platinumPlatinum and palladiumPalladium followed the Freundlich and Langmuir adsorptionAdsorption isotherm, respectively.

Following the global trend towards electric transportation, automakers are transitioning from internal combustion engines to electric vehiclesElectric vehicles. To overcome the expected increase in spent batteries, recyclingRecycling li-ion batteries is vital in securing the raw materials. While the pyrometallurgical route offers an effective metallurgical separation, its drawback lies in the high energy consumption from the high-temperature requirement. A high-temperature process by a cleaner energy source like concentrated solar energy is an alternative to address this issue. Solar energy proves promising due to its renewable nature. In this study, the battery waste containing various cathode metals was extracted through carbothermic reduction using anode carbon in a solar simulator furnace. A thermodynamic assessmentThermodynamic assessment was conducted using the FactSage™ thermochemical package in conjunction with selected experimental data within the temperature range of 400–800 °C. The development of a concentrated-solar-thermal-driven recyclingRecycling route is a necessary step towards a sustainableSustainable process for recyclingRecycling spent liLithium-ion batteries.

LithiumLithium is one of the critical elements required for clean energy technology to achieve a carbon-neutral target. In this study, the beneficiation ofLow-grade spodumene ore a low-grade spodumene ore (0.3–0.6% Li2O) from Eastern Kazakhstan is investigated by dense medium separation (DMS)Dense Medium Separation (DMS) and froth flotationFlotation to obtain lithiumLithium concentrate. The main gangue minerals in the spodumene ore are feldspar, quartz and mica. The highest lithiumLithium grade in concentrate from DMSDense Medium Separation (DMS) of 1000/+ 850 µm size fractions of the low-grade spodumene oreLow-grade spodumene ore is achieved at approximately 5.7% from 0.6% (Li2O), with a recoveryRecovery of about 90%. Furthermore, the spodumene ore is beneficiated by reverse flotationFlotation using NaOL and DAA as mixed collectorsMixed collector. The maximum lithiumLithium recoveryRecovery of approximately 30% with the highest lithiumLithium grade of 1.0% was obtained from a low-grade spodumene oreLow-grade spodumene ore under flotationFlotation condition of 1000 g/t NaOL/DAA, ratio of 1:5, pH 10. Conditioning the pulp with starch has little effect on the flotationFlotation recoveryRecovery of lithiumLithium from low-grade spodumene oreLow-grade spodumene ore improving lithiumLithium grade from 1.0 to 1.45%.

The current study investigated the effects of thiol collectors on the flotation of base metals (BMs) and platinum group metals (PGMs) ores. The properties of a single-mineral flotation test were conducted using sodium isobutyl xanthate (SIBX), sodium ethyl xanthate (SEX), potassium ethyl xanthate (PEX), and sodium isopropyl xanthate (SIPX) at concentrations of 40, 60, 80, 100, and 120 g/t and pH 9. Rougher flotation recoveries higher than 85% were obtained at typical rougher mass pulls using these xanthates at various dosages, which demonstrated high selectivity properties towards both ores. The dosages of these collectors were monitored by UV-Vis in solution as a function of time at a constant pH. The UV-Vis results showed high mineral-collector interaction between the mineral surface and xanthate at 300 nm. The thiol collectors (SIPX, SEX, SIBX, and PAX) were found to be selective towards PGMs and BMs as similar increased cumulative recoveries were obtained. The structures of xanthates had an impact on the flotation recovery. For instance, iso-alkyl xanthate (SIBX) showed better consistency in terms of maximum cumulative recovery at various dosages when compared to other xanthates.

The recoveryRecovery of heavy metals from municipal solid wasteMunicipal solid waste incinerated fly ashIncinerated fly ash (MSW-IFA) before its final disposal is highly desirable for sustainableSustainable waste management and resource recoveryRecovery. RecyclingRecycling of zinc via leaching-solvent extractionSolvent extraction techniques has been studied, therefore yielding > 90% efficiency of zinc dissolution at a H2SO4 concentration of 1.5 mol/L, a temperature of 90 °C, a S/L ratio of 150 g/L, a time of 2 h, and a stirring speed of 300 rpm. Further, zinc was efficiently extracted using 0.6 mol/L D2EHPAD2EHPA at an equilibrium pH of 2.0 and an organic-to-aqueous phase ratio of 1. Finally, the highly pure zinc solution could be quantitatively stripped in a solution containing 1.5 mol/L H2SO4. This could lead to a circular economy of zinc with MSW-IFA as a possible secondary source.

GermaniumGermanium, galliumGallium, and indiumIndium are valuable elements due to their great economic importance and growing utilization in high-tech and green-tech applications. The exploitation of secondary resourcesSecondary resource, for example, tailings, slags, or end-of-life products, as well as the application of sustainableSustainable biotechnological methods, results in the challenge of separating Fe(III) from In(III), Ge(IV), or Ga(III). With common methods, such as precipitation, the selectivitySelectivity for In, Ga, and Ge is often insufficient. The application of innovative solvent extractionSolvent extraction processes is a promising approach to separate valuable metals from iron in order to make them available for an efficient recoveryRecovery. In this study, we present the development of extraction methods using amine extractantsAmine extractants for the selective separation of Fe(III) from In(III), Ga(III), and Ge(IV) in sulphate solutions. The influence of different parameters, e.g. the pH value and the composition of the organic phase, as well as possibilities to re-extract iron from the loaded organic phase, will be discussed.

In recent times, ammoniacal leaching has received widespread attention in extractive metallurgyExtractive metallurgy, mainly to process the lateritic ores of nickelNickel. Copper has always been found as the companion metal ion in ammoniacal solutions, whose effective separation is highly desirable to achieve product purityPurity. Usually, LIX series extractants are applied to co-extract and their selective stripping is a function of acid concentration, resulting in large hold-up volumes of the solvent. Henceforth, to achieve high selectivitySelectivity in the extraction step, we studied the antagonistic effect of tributyl phosphate (TBP)TBP mixing with LIX 84-ICLIX 84-IC, which inhibited nickelNickel extraction with copper from the ammoniacal solution. The determined distribution coefficient values as D(mix) <  < D(LIX 84-IC) + D(TBP) and negative ∆D values clearly demonstrate the antagonistic effect caused by the extractant mixture. The highest separation factor, i.e., β(Cu/Ni) = 1330, was obtained at a molar mixture of LIX 84-IC:TBP = 0.4:0.6 and an organic-to-aqueous (O:A) phase ratio of 1. The extraction thermodynamics indicate an endothermic process (ΔH° = 5.4 kJ/mol) that forms the inner-sphere organometallic complexation. The copper-loaded organic phase was quantitatively stripped by contacting it with a 1.0 mol/L H2SO4 solution at an O:A ratio of 1.

Most common separation processes in hydrometallurgical processes are ion exchangeIon exchange and precipitation. However, novel technologies have been developed aiming at greener technologies and lower energy consumption and greenhouse gas emissions. Membrane technologiesMembrane technology are being studied as a potential separation technique in hydrometallurgical processes including ultrafiltration, nanofiltration, and electrodialysis. Supported liquid membranes have been studied due to their selectivitySelectivity and easy synthesis supported with organic extractants. This study aimed at the evaluation of Co(II) separation from Ni(II) through a membrane supported with phosphinic acid extractant. Experiments were carried out with two chambers at 25 °C, where the feed chamber contained the metals in sulfuric media and receiving acid solution. The membrane was prepared with PTFE/PVDF and Cyanex 272 10% diluted in kerosene as carrier. The effect of membrane preparation, Cyanex concentration, and pH in receiving chamber were evaluated. Results demonstrated the Ni/Co separation factor reached 4 without the use of concentrated acid for stripping.

The process of galliumGallium extraction from fly ash produces a large amount of acidic wastewater. The presence of Fe3+ andFe3+ heavy metal ions in the wastewater after galliumGallium recoveryRecovery makes it impossible to return to the fly ash leaching process for recyclingRecycling. In this study, 2-Octanol2-Octanol diluted with sulphonated kerosene was used to extract Fe3+ fromFe3+ the acidic wastewater. In a six-stage counter-current with the conditions of O/A = 2/1, 25 °C, 5 min, 4.5 mol/L of HCl, the extraction of Fe3+ can reach more than 99%. Over 99.9% of Fe3+ could be stripped in a six-stage counter-current batch simulation test using 0.1 mol/L HCl. The mechanism ofFe3+ Fe3+ extraction using 2-Octanol2-Octanol was discussed according to FT-IR spectra results.

Pressure oxidationPressure Oxidation (POX) is the most utilized method for chemically liberating gold from sulfides. However, in the context of decreasing gold grades and increasingly complex mineralogy as well as variable qualities of process solutions, operations using POX can be challenged by high reagent consumption and in ensuring high gold recoveriesRecovery. While POX technology is considered mature, a complete understanding of the phase transformations and gold deportment has yet to be described. In this work, by manipulating autoclave conditions, we report on batch pressure oxidationPressure Oxidation experiments where jarositeJarosite-only and hematiteHematite-only precipitates are obtained. The pressure oxidationPressure Oxidation reaction kinetics are monitored in-situ, via oxidation–reduction potential and pH measurements and interpreted with respect to recently calibrated equilibrium chemical thermodynamic data for the Fe(II)-Fe(III)-SO4-H2O system. Using a combination of assays, X-ray diffraction, and high-resolution SEM–EDS spectroscopy of feed and residue samples, insight into the chemical reactions taking place and gold redistribution is obtained. This research approach of combining in-situ measurements, chemical equilibrium and advanced sample characterisation will help in establishing new ways to improve process operations with existing process infrastructure.

In this study, we develop a selective precipitation process for the recoveryRecovery of titaniumTitanium, magnesium, and aluminum from the steel slagSteel slag leach liquor. To accurately predict the precipitation behavior of the target elements in the complex sulfate system, we conduct thermodynamic modelingThermodynamic modeling and experimental measurement of metal hydroxide precipitation titration curvesTitration curve. The investigation focuses on three key operating parameters: initial solution pH, initial metal ion concentration, and reaction temperature. We examine the ion interaction, precipitation pH, amount of precipitant required, and species equilibrium. Subsequently, hydroxide precipitation testing is performed using sodium hydroxide as a single precipitant to selectively recover the target elements. We evaluate the effects of precipitation pH level, reaction temperature, stabilization time, and precipitant reagent type on metal recoveryMetal recovery and product purityPurity. Following process optimization, we achieve an 83% purityPurity of titaniumTitanium precipitate with 85% recoveryRecovery, along with > 90% purityPurity of magnesium and aluminum precipitates with 100% recoveryRecovery.

Due to their high thermal and mechanical stability, increasing demands for high-grade molybdenumMolybdenum compounds for improved steel properties warrant continuous extraction for defined industrial applications. In this study, molybdenum-cum-silica compound preparation from indigenous molybdeniteMolybdenite was examined via oxidative roasting and chemical leaching. The influence of pertinent parameters such as leachant concentration, reaction temperature, and particle size on the extent of molybdeniteMolybdenite ore reacted was thoroughly investigated. The degree of molybdenite dissolution rate increased from 52 to 90% at optimal conditions. The leach liquor obtained at optimal conditions was purified through solvent extractionSolvent extraction technique and beneficiated to an Industrial Sodium Aluminosilicate (ISA)/Industrial Sodium Molybdate Dihydrate (ISMD)Industrial Sodium Molybdate Dihydrate (ISMD) compound. This prepared compound as characterized is recommended as industrial raw material in some defined steel operationsSteel operations.

The preparation of aluminum-vanadium (Al-V) intermediate alloys through the electrolysis of NaVO3NaVO3 in the Na3AlF6-K3AlF6-AlF3 molten saltMolten salt system using liquid aluminum as cathode is a novel process. In the present study, the forms of the Al-V intermetallic compounds and the contents of vanadiumVanadium in the intermediate alloys were investigated at different current densitiesCurrent density. The results showed that the cathode product contained aluminum matrix and Al10V at a current densityCurrent density of 0.6 A/cm2. As the current densityCurrent density increased to 0.7 A/cm2, the Al3V phase started to form while the vanadiumVanadium content was still very low in the cathode product. At 0.8 A/cm2, the vanadiumVanadium content in the cathode alloy product reached 7.83 wt.% with a current efficiency of 34.54%. However, no significant change in the vanadiumVanadium content was noticed at current densitiesCurrent density of 0.9 and 1.0 A/cm2.

Rare earthRare earths electrolysis from fluoride melts has a lot in common with aluminium electrolysis; however, there are significant differences that need to be understood and investigated in order to develop efficient process control. A laboratory setup was developed to efficiently trap gases and obtain a mass balance of the components in the gas phase to understand the anode reactions. Using the described setup with a NdF3-LiF electrolyte, it was possible to concentrate the off-gas (CO and CO2) to approximately 10% facilitating increased sensitivity of PFC components. The laboratory cell produced metal, and the metal yieldYield was 83% based on mass balance of CO + CO2. The results are also discussed in context of results obtained in a small pilot cell designed and operated for metal production.

A parameter study of DyFeDyFe Electrowinning alloy production by molten salt electrolysisMolten Salt Electrolysis in an equimolar DyF3-LiF electrolyte added Dy2O3 at temperatures in excess of 1000 °C using a power supply system that could deliver up to 500 A is reported. A cylindrical carbon anode with a pure iron cathode in the centre was used. Oxide concentration of electrolyte determined by inert gas fusion technique varied from ca. 1.5–3 wt%. The formation of perfluorocarbon (PFC) gases was monitored using an online Fourier Transform Infrared Spectrometer (FTIR). The investigations showed a close relationship between the cathodic current densityCathodic Current Density and the amount of DyFe metal alloy produced with the highest metal production occurring at cathodic current densitiesCathodic Current Density above 6 A/cm2. Inductively coupled plasma (ICP) analysis of the produced DyFe metal ingots showed a composition of 83 wt% Dy and 17 wt% Fe. Carbon content varied between 0.04 and 0.16 wt%.

Choline Chloride-Ethylene Glycol DES mixture (ethaline) is considered a green solventGreen solvents and is one of the most popular DESs to combine with electrochemical recoveryRecovery processes due to its superior electrochemical properties compared to other DES systems. In this work, electrochemical behaviour of antimonyAntimony, telluriumTellurium, and indiumIndium in the ethaline system has been investigated to evaluate if this electrolyte media is suitable for electrochemical recoveryRecovery. The metal chlorides SbCl3, TeCl4, and InCl3 were added to model ethaline solutions at 10 mM concentrations. Electrochemical investigations were carried out at 60 °C by cyclic voltammetry (CV), chronoamperometry (CA), and potentiostatic electrolysis using a three-electrode setup. Metal deposits were investigated with SEM–EDS. All three metals were found to deposit within the electrochemical limits of the ethaline electrolyte, the cathodic deposition of the different metals appears in the order Te, then Sb, then In most cathodic.

Rare earthRare earths oxides possess exceptional physical and chemical properties, making them extensively utilized in various fields such as new materials, catalysis, and biomedicine. However, the current production process of Y2O3Y2O3 inevitably results in the emission of pollutants like ammonia and nitrogen oxides. This article aims to address this issue by proposing the preparation of Y2O3 through theYCl3·6H2O YCl3·6H2O electro-metallurgicalElectro-metallurgical method. In this method, an aqueous solution of YCl3·6H2O isYCl3·6H2O employed as the raw material, and through cation exchange membrane electrolysis technology, Y(OH)3 precipitate with a layered structure is obtained at the cathode. The thermal decomposition process of yttrium hydroxide was investigated using XRD, FTIR, and DSC-TGA. Furthermore, the microstructure and particle size of the phases were analyzed using SEM and a laser particle size analyzer, demonstrating that the Y2O3Y2O3 product inherits the precursor's structure. The electro-metallurgicalElectro-metallurgical process offers several advantages, including mild reaction conditions, simple equipment, and environmental friendlinessEnvironmental friendliness.

The process of obtaining antimonyAntimony trioxide from Unified Mining Company S.A. (EMUSA) has two production lines. The refining slagRefining slag from the second production line was stored since the plant started operations, registering high antimonyAntimony contents which is the reason for this research project. To recover antimonyAntimony from the slag, it was necessary to carry out a reducing fusion with slag using pyrometallurgical methods with ternary diagrams; $${\text{FeO}}{:}{{\text{Na}}}_{2}{\text{O}}{:}{{\text{SiO}}}_{2}$$ FeO : Na 2 O : SiO 2 and $${\text{FeO}}{:}{{\text{SiO}}}_{2}{:}{\text{CaO}}$$ FeO : SiO 2 : CaO the Sb recoveryRecovery was done in two parts; the first part consisted of melting in a flame furnace and the second a melting in the IIMETMAT thermobalance. The flow of oxygen necessary for antimony recoveryAntimony recovery was 0.1 $${\text{l}}/{\text{min}}$$ l / min higher flows oxidize antimonyAntimony and lower recoveryRecovery. The experiments showed that the reaction that controls the process is $${{\text{PbSb}}}_{2}{{\text{O}}}_{6}+6{\text{C}}=2{\text{Sb}}+{\text{Pb}}+6{\text{CO}}$$ PbSb 2 O 6 + 6 C = 2 Sb + Pb + 6 CO . For the melting in the flame furnace, the best slag ratio used was 35:15:50 with the system and with the system, the best ratio was 35:15:50, with Sb recoveriesRecovery of 98% in both cases.

The recyclingRecycling of cemented carbides (CC) is an indispensable facet of resource conservation, especially for critical raw materials, signifying its profound environmental, economic, and strategic importance. These complex materials, consisting of refractory carbides embedded in a metallic binder, mainly tungsten carbide and cobaltCobalt, offer versatile recyclingRecycling options. Among these methods, the zinc processZinc process is emerging as the most promising with significant potential regarding energy consumption and quality of products. In this method, zinc reacts with cobaltCobalt binder to form intermetallic phases, resulting in a breakdown of the material's composite structure due to the higher volume of these phases. In the second step, Zn evaporates at high temperatures under vacuum, leaving behind a porous cemented carbide skeleton. By means of crushing, grinding, and sifting, these can be processed into a powder mixture suitable for direct use in the manufacture of new products. While previous research has focused on the formation of Co-Zn phases during the decomposition step, there is a gap in understanding the growth rate of the disintegration layer. Therefore, this study aims to investigate the layer growthLayer growth and the kinetics of the disintegration stage of the zinc processZinc process. By examining these aspects, a deeper understanding of the fundamental mechanisms at play in this method is gained, contributing to further advancements in the recyclingRecycling of cemented carbides.

An effect previously observed in magnet recyclingMagnet recycling experiments is further investigated in this work. At high temperatures (1800 °C) and moderate vacuum (0.01 bar) certain heavy rare earth elementsRare earth elements are found to selectively partition into a metallic iron phase produced by thermal decomposition from a molten sulfide phase. Works in the literature have established that rare earth elementsRare earth elements suppress the concentration of sulfur strongly in liquid iron at 1600 °C, but the behavior of heavy rare earth elementsRare earth elements in this context remains uncertain. Herein, experimental results using magnet simulants with heavy rare earth elementsRare earth elements – terbium, dysprosium, and erbium – are reported, using concentrations 10 × higher than in magnets, in order to investigate the possible saturation of the iron phase. SEM/EDS analysis showed that terbium and dysprosium partitioned to the metal at low concentrations, approximately 0.50% by weight.

The study investigates the microstructure and mechanical properties of five cast, coarse-grained intermetallic alloys: binary Al11Ce3 and Al11La3, ternary Al11(Ce0.75La0.25)3 and Al11(Ce0.5La0.5)3, and quaternary Al11(Ce0.54La0.27Nd0.19)3 with mischmetal composition. All compounds exhibit a single phase indicating a solid solution among the rare-earth elements (RE = Ce, La, and Nd) on the Ce sublattice of Al11RE3, contrary to Thermo-Calc prediction of segregation of Ce and (La, Nd) into two insoluble compounds. The orthorhombic Immm-structured α-Al11RE3 phase’s lattice parameters increase with increasing La concentration, while the α-β phase transformation temperature decreases. The mechanical properties, encompassing high hardness (4.1–4.3 GPa), low indentation fracture toughness (0.48–0.65 MPa m1/2), together with the high twinning propensity among these five Al11RE3 compounds are remarkably similar. This similarity suggests that these Al11RE3 compounds will exhibit comparable strengthening in Al-RE-based eutectic alloys, while also positioning them as economically and environmentally favorable alternatives to the well-developed binary Al11Ce3 compound formed in current eutectic Al-Ce alloys.

The effect of different oxides in vanadium slagVanadium slag, such as MgO, MnO, and Al2O3 on vanadium extractionVanadium extraction in the sodium roasting-water leaching process has been investigated. The results show that the increase of these oxides has a positive influence on the conversion rateConversion rate of vanadiumVanadium. At the condition of sodium roasting, with the increase of MgO, MnO, and Al2O3 contents to 11.49%, 14.22%, and 11.13%, the conversion ratesConversion rate of vanadiumVanadium increased from 89.9% to 97.3%, 98.0% and 95.8%, respectively. With increasing MgO content, more vanadiumVanadium transformed into spinel phase. The roasting and leaching parameters have also been optimized. 97.3% of vanadiumVanadium could be extracted from high MgOHigh MgO vanadium slagVanadium slag at the following conditions: roasting temperature of 800 °C, V/Na molar ratio 0.2; leaching time of 60 min, liquid/solid ratio of 10:1. The results can provide a fundamental basis to the modification of vanadium slagVanadium slag based on slag splashing in vanadium extractionVanadium extraction converter.

This study develops a green and efficient hydrometallurgical process for the recoveryRecovery of Zn and CdCd from Zn-rich dust after pyrometallurgical treatment of iron and steel metallurgical dust. The feasibility of separating Zn, Cd, and Fe in the leaching system was confirmed by thermodynamic analysisThermodynamic analysis. In the acid leaching process, dilute H2SO4 is used as the leaching agent, Zn and CdCd are leached and recovered in the liquid in the form of Zn2SO4 and Cd2SO4. This article studies the leaching behavior of CdCd and Bi under different experimental conditions (such as H2SO4 concentration, liquid-to-solid ratio, temperature, and reaction time). Under the optimal conditions, the leaching rates of CdCd and Bi are 93.15% and 0.78% respectively. In the second step, the CdCd in the leaching solution is extracted through the replacement process to prepare Cd products to realize resource utilization.

Magnesiation roastingMagnesiation roasting-acid leaching is carried out to extract vanadiumVanadium from high calcium and high phosphorus vanadium slagHigh calcium and high phosphorus vanadium slag (HCPVS). The effects of roasting and leaching conditions on vanadiumVanadium and phosphorus extraction are studied. In optimal conditions, the extraction efficiency of vanadiumVanadium reaches 79.7%, and only 35.6% of phosphorus is leached owing to Mg2+ inhibiting the leaching of phosphorus. The roasting mechanism is analyzed by XRD and BSE-EDS systematically, best of the vanadiumVanadium in V-spinel is converted into vanadate, and a small part of vanadiumVanadium is dissolved into Ca2SiO4Ca2SiO4–Ca3(PO4)2 and CaTiO3CaTiO3 phase. This work reveals the influence mechanism of Ca2SiO4Ca2SiO4–Ca3(PO4)2 and CaTiO3 phase on vanadium extractionVanadium extraction, providing new insights for vanadium extractionVanadium extraction from HCPVS.

Theoretical research on the separation of telluriumTellurium by vacuum distillationVacuum distillation from crude seleniumCrude selenium could provide further key data support for industrial production. In this work, theoretical and experimental studies on the separation of telluriumTellurium impurities from crude seleniumCrude selenium by vacuum distillationVacuum distillation were systematically carried out. The saturated vapor pressure, separation coefficient, vapor–liquid equilibrium composition, average molecular free path, and evaporation rate characteristics of selenium and telluriumTellurium under different distillationDistillation conditions were calculated theoretically. We conducted research on the volatilization characteristics of crude seleniumCrude selenium and measured the volatilization rate of crude seleniumCrude selenium under pressures of 498–573 K and 10–500 Pa using the vacuum differential method. The volatilization rate values of crude seleniumCrude selenium under different conditions were obtained, and the influences of distillationDistillation temperature and system pressure on the volatilization rate of crude seleniumCrude selenium were uncovered.