Strategic Metals Research Articles

The electrolysis-graded leaching process for rapid resource regeneration of Th(IV)/U(VI) from wastewater

Uranium and thorium are strategic metals, and the mining and utilization of uranium and thorium produce a large amount of radioactive wastewater. In this paper, a new process combining electrolysis and leaching is proposed to achieve resource regeneration of uranium and thorium from radioactive wastewater. The results revealed that carbonate was the optimal separation system. The uranium-thorium separation was based on the formation of soluble UO2(CO3)34− and insoluble ThO2. And the separation efficiency was determined to reach a maximum value of 4.8 × 104 at pH 10.5. Surprisingly, UO2(CO3)34− could be effectively electrochemically recovered, and more than 90% of uranium could be recovered within 3 h, which indicated that uranium could be efficiently recovered. In addition, U–Th leaching studies were performed, and the results showed that selective leaching of uranium could be achieved at 0.01 M, while effective leaching of Th could be achieved at 0.3 M, thus establishing a graded-leaching process for U–Th. To reduce the impact of Ba2+ on the uranium electrochemical separation process, the SO42--CO32- combined system was developed, and the concentration of Ba2+ was reduced by two orders of magnitude. The final result revealed that the purity had been roughly tripled via this process. This study provides an effective strategy to reduce the waste of non-renewable uranium-thorium resources and process wastewater, achieving the recycling of non-renewable resources and the sustainable development of nuclear energy.

Highly selective capture of gallium from aqueous solutions using tetradentate amidoxime functionalized MIL-53(Al) nanofiber membranes

Gallium, with an average content of about 15 μg g−1 in the Earth's crust, ranks at the forefront of strategic metals. However, the separation of gallium remains challenging due to the similar physical and chemical properties of gallium and other impurity ions. Herein, the tetradentate amidoxime-functionalized MIL-53(Al) nanofiber membranes (PAN/MIL-53-AO) are prepared to separate gallium, aluminum, vanadium ions and so on. The resultant membranes display 231.08 mg g−1 for Ga(Ⅲ) with high selectivity in static and dynamic adsorption. Specially, PAN/MIL-53-AO demonstrates excellent gallium regeneration rate of 84.25% after five cycles. According to DFT calculations, due to the tetradentate structure of MIL-53(Al)-AO, the amidoxime group binds to gallium ion with a lower binding energy (−29.46 eV). In conclusion, the experimental dates and theoretical calculations indicate that the excellent adsorption capacity is derived from the high binding ability of unique rhombic tetragonal coordination structure for gallium ion and the specific MIL-53(Al) cavity size for passage of gallium. Such performances outperform most state-of-the-art adsorption membranes. The special structure of MOF pores provides a novel approach for rapid synthesis of adsorption sites with high selectivity, with potential utilization in the selective adsorption of gallium ions.

Cytogenetic damage by vanadium(IV) and vanadium(III) on the bone marrow of mice

Vanadium is a strategic metal that has many important industrial applications and is generated by the use of burning fossil fuels, which inevitably leads to their release into the environment, mainly in the form of oxides. The wastes generated by their use represent a major health hazard. Furthermore, it has attracted attention because several genotoxicity studies have shown that some vanadium compounds can affect DNA; among the most studied compounds is vanadium pentoxide, but studies in vivo with oxidation states IV and III are scarce and controversial. In this study, the genotoxic and cytotoxic potential of vanadium oxides was investigated in mouse bone marrow cells using structural chromosomal aberration (SCA) and mitotic index (MI) test systems. Three groups were administered vanadium(IV) tetraoxide (V2O4) intraperitoneally at 4.7, 9.4 or 18.8 mg/kg, and three groups were administered vanadium(III) trioxide (V2O3) at 4.22, 8.46 or 16.93 mg/kg body weight. The control group was treated with sterile water, and the positive control group was treated with cadmium(II) chloride (CdCl2). After 24 h, all doses of vanadium compounds increased the percentage of cells with SCA and decreased the MI. Our results demonstrated that under the present experimental conditions and doses, treatment with V2O4 and V2O3 induces chromosomal aberrations and alters cell division in the bone marrow of mice.

Innovative Environmentally Safe Processes for the Extraction of Rare and Rare-Earth Elements from Complex Ores of Perplexed Material Composition

Domestic and world tendencies of involvement in the processing of ores of rare metals (RMs) and rare-earth metals (REMs) are shown. It is shown that the main direction of innovative activity is the development and application of modern breakthrough technologies for complex processing of mineral raw materials with the production of high-quality products while minimizing environmental damage. The main deposits of rare and rare-earth metals are systematized from the standpoint of the content of the main components, concentrator minerals and the main enrichment methods. The main principal technological schemes of processing of some deposits of RMs and REMs in Russia (Lovozer, Tomtor, and Afrikand deposits) are given. Options for involving technogenic and off-balance raw materials in the processing in order to extract strategic metals are considered. It is substantiated that innovative environmentally friendly processes for the extraction of rare and rare-earth metals from complex ores of complex material composition are being actively developed in Russia at present.

Flotation and adsorption of novel Gemini decyl-bishydroxamic acid on bastnaesite: Experiments and density functional theory calculations

Rare earth element is an important strategic metal, but the supply of high purity rare earth ores is growing slowly, which is in sharp contradiction with the rapidly growing demand. Froth flotation has been confirmed to be an effective method to separate bastnaesite from its gangue minerls. However, the traditional collectors are facing serious problems in flotation separation of minerals, requiring the addition of excess depressant and regulator in the flotation process. Herein, we proposed and synthesized novel Gemini hydroxamic acids Octyl-bishydroxamic acid (OTBHA), Decyl-bishydroxamic acid (DCBHA) and Dodecyl-bishydroxamic acid (DDBHA) as the collectors in bastnaesite-barite flotation system. The effect of different carbon chain lengths on the molecular properties were explored by density functional theory (DFT) calculations. DCBHA possessed a stronger reactivity compared with OCBHA and DDBHA. The flotation results verified the consistency of the computational calculation about the performance prediction of Gemini hydroxamic acids. Compared with OCBHA and DDBHA, DCBHA displayed superior collecting affinity toward bastnaesite, and did not float barite. Zeta potential results showed that the presence of DCBHA increased the potential of bastnaesite, while it had almost no effect on barite, indicating DCBHA had a stronger affinity for bastnaesite. Then, Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses indicated that the adsorption mechanism was due to two hydroxamate groups of DCBHA co-anchored on bastnaesite surface by forming five-membered hydroxamic―(O―O)―Ce complexes. In addition, atomic force microscopy (AFM) clearly observed that DCBHA uniformly aggregated on bastnaesite surface, which increased surface contact angle and improved the hydrophobicity of bastnaesite.

Recent Work on the Recovery of Rare Earths Using Ionic Liquids and Deep Eutectic Solvents

With the development of smart technologies, the use of rare-earth elements (REEs) has been widespread; thus, their importance as valuable and strategic metals has been boosted to levels never known before. Due to their scarcity in the Earth’s crust, the recovery of these elements from secondary resources has also witnessed further developments. Traditional pyrometallurgical and hydrometallurgical processing techniques, though widely used in the recovery of these REEs, have some environmental drawbacks; thus, new recovery approaches are under development. Here, Solvometallurgy has emerged as an environmentally friendly technology, and ionic liquids and deep eutectic solvents have turned out to be first-line chemicals to be used in the different unit operations employed in solvometallurgical processing, i.e., leaching, liquid–liquid extraction, ion exchange (adsorption), precipitation, and electrolysis. This manuscript reviews the most recent literature (2002–June 2023) concerning the use of ionic liquids and deep eutectic solvents in the recovery of REEs from various sources.

Full-cycle chains of strategic mineral raw materials – new opportunities for the Russian North

The paper analyzes the relationship between the global energy transition and the possibilities of Russia and its northern regions to enter the world markets for strategic raw materials and components necessary for a green economy. The acceleration of the energy transition in developed countries leads to an increased demand for strategic metals and their compounds (primarily REM and lithium). Solar and wind energy are becoming the largest energy producers in the world. Thanks to these processes, countries with technological competencies and resource capabilities in the field of «green» metals can significantly strengthen the potential of their own industries[1]producers and consumers of strategic raw materials. The role of technological value chains localized within the country is growing. A feature of Russia is the imbalance between the extraction of strategic mineral raw materials and the production of high-tech products based on it. This means the fragmented nature of value chains. The directions of the evolutionary path of transition to the interaction of different participants in the chain are proposed based on the formation of full-cycle chains focused on creating demand for high-tech raw materials within the country. Thus, the deposits of strategic raw materials in the northern regions of Russia can and should be based on chains «from ore mining to the production of high-tech products».

The anthropogenic cycles of palladium in China during 2001–2020

Palladium (Pd) is a strategic metal and can help reduce environmental pollution, especially from vehicle exhausts. China is the world's largest Pd consumer, but with very limited reserves. However, Pd anthropogenic cycles remain unclear in China. This study aims to uncover the dynamic Pd flows and stocks in China for the period of 2001–2020 by conducting dynamic material flow analysis. The results show that the demand for Pd had increased by 10 folds during the study period due to stricter vehicle emissions policies. Also, China mainly imported such resource from the United States, Western Europe, and East Asia, with a share of 88.8 %. However, due to insufficient end-of-life vehicle (ELV) recycling system, the total recycled Pd was only 12.3 tons although the end-of-life Pd flow increased from 3.7 tons in 2001 to 30.8 tons in 2020. This implies a great Pd recycling potential. Therefore, it is urgent to promote Pd recycling by establishing an effective Pd recycling system. In addition, other policy recommendations, such as diversifying Pd import partners, increasing Pd emergency reserves, and economic instruments, are raised by considering the Chinese realities so that the overall Pd resource efficiency can be improved.

Improving the sorption properties of mesoporous carbons for the removal of cobalt, nickel and manganese from spent lithium-ion batteries effluent

The competitive sorption of Co2+, Li+, Ni2+, and Mn2+, strategic metals from spent lithium-ion batteries and their leachates, was studied using activated mesoporous carbons. The mesoporous carbon was synthesized by the replica method using silica gel as a template and exhibited a high surface area with an accessible pore volume due to mesopores (Vmeso > 95%). Fast kinetics and high sorption capacities of these metals were achieved with the chemical activation of mesoporous carbons. The surface modification of the mesoporous carbon was carried out by physical activation with O2 at 450 °C and chemical activation under mild conditions (room temperatures) with NaClO2/H2O2 as oxidizing agents. FTIR analysis and conductimetric titration showed that the combination of an initial physical activation step, followed by chemical functionalization, maximized the formation of carboxylic acids (from 0.2 to 0.9 meq/g), due to the complete oxidation of the weakly acidic groups. Those carbons were tested in sorption experiments of the lithium-ion battery metals in monometallic solutions, where physically activated and chemically reactivated mesoporous carbon selectively removed over 80% of Co2+, Ni2+, and Mn2+, with sorption capacities over 20 mg/g, while only 20% of Li+ was removed. This carbon stood out amongst the others studied (2 to 11-fold increase in sorption capacities depending on the metal) and was tested in multimetallic solutions, showing fast removal rates, reaching equilibrium within the first 15 min, as well as selectivity towards divalent cations (18 mg/g of Co2+) with insignificant lithium sorption (qLi = 0.33 mg/g). Desorption of metals was carried out using H2SO4, which allowed the recovery and twofold of the initial concentrations of Co, Ni, and Mn.

Surface structure regulating of silica adsorbent for the selective adsorption of heavy rare earth

Rare earth element (REE) is a strategic metal resource, heavy REE owns higher economic and strategic value compared with light rare earth elements. However, it is a great challenge for the separation of heavy rare earth ion efficiently in the solution with mixed rare earth ions due to the similar physicochemical properties of heavy and light REE. In this paper, the diglycolamide (DGA) modified silica adsorbents were prepared and applied to the selective adsorption of heavy earth ion Dy3+. The structure of DGA on the silica surface was regulated during the modifying processes to obtain DGAb-SiO2 and DGAs-SiO2 adsorbent, which was verified by FTIR and NMR characterization results. The adsorption results showed that the DGAb-SiO2 adsorbent owned a much higher distribution coefficient (Kd) value for the selective adsorption of Dy3+ than the DGAs-SiO2 adsorbent. The higher adsorption selectivity is likely due to the fixed carbon chain of the DGA group on the surface of DGAb-SiO2 adsorbent formed rigid spatial structures of the oxygen atoms, which will be favorable for the selective coordination of Dy3+. Besides its effectiveness in adsorption behavior, the DGAb-SiO2 adsorbent displayed excellent stability. The Kd value of DGAb-SiO2 for Dy3+ selective adsorption maintained a high level after four successive recycling runs. The adsorption kinetics results displayed that the adsorption of Dy3+ followed pseudo-second-order kinetic, and the adsorption process fitted the Langmuir isotherm model. Additionally, the same adsorption rules for the rare earth ions were observed over DGA-KIT-6 adsorbent, indicating the high universality of the surface modification to the adsorbent support, which will provide an intentional reference for the surface modification to other adsorbent support.

INNOVATIVE ENVIRONMENTALLY SAFE PROCESSES FOR RECOVERY OF RARE AND RARE-EARTH ELEMENTS FROM COMPLEX ORES OF COMPLEX MATERIAL COMPOSITION

Domestic and world tendencies of involvement in the processing of ores of rare and rare earth metals (REM) are shown. It is shown that the main direction of innovative activity is the development and application of modern breakthrough technologies for the complex processing of mineral raw materials with the production of high-quality products while minimizing environmental damage. The main deposits of rare and rare-earth metals are systematized from the standpoint of the content of the main components, concentrator minerals and the main enrichment methods. The main principal technological schemes of processing of some deposits of RM and REM in Russia (Lovozerskoe, Tomtorskoe, Afrikandskoe deposits) are given. The options for involving technogenic and off-balance raw materials in the processing in order to extract strategic metals are considered. It is substantiated that innovative environmentally friendly processes for the extraction of rare and rare earth metals from complex ores of complex material composition are being actively developed in Russia at present

Yeast Deletomics to Uncover Gadolinium Toxicity Targets and Resistance Mechanisms.

Among the rare earth elements (REEs), a crucial group of metals for high-technologies. Gadolinium (Gd) is the only REE intentionally injected to human patients. The use of Gd-based contrasting agents for magnetic resonance imaging (MRI) is the primary route for Gd direct exposure and accumulation in humans. Consequently, aquatic environments are increasingly exposed to Gd due to its excretion through the urinary tract of patients following an MRI examination. The increasing number of reports mentioning Gd toxicity, notably originating from medical applications of Gd, necessitates an improved risk-benefit assessment of Gd utilizations. To go beyond toxicological studies, unravelling the mechanistic impact of Gd on humans and the ecosystem requires the use of genome-wide approaches. We used functional deletomics, a robust method relying on the screening of a knock-out mutant library of Saccharomyces cerevisiae exposed to toxic concentrations of Gd. The analysis of Gd-resistant and -sensitive mutants highlighted the cell wall, endosomes and the vacuolar compartment as cellular hotspots involved in the Gd response. Furthermore, we identified endocytosis and vesicular trafficking pathways (ESCRT) as well as sphingolipids homeostasis as playing pivotal roles mediating Gd toxicity. Finally, tens of yeast genes with human orthologs linked to renal dysfunction were identified as Gd-responsive. Therefore, the molecular and cellular pathways involved in Gd toxicity and detoxification uncovered in this study underline the pleotropic consequences of the increasing exposure to this strategic metal.

Geological characterization and controlling factors of small-scale variations in the cobalt-rich ferromanganese crust deposits

Cobalt-rich ferromanganese crusts (CRC) are potential resources for Co, Ni, Pt, and other strategic metals. The CRC thickness varies from a few mm to more than 100 mm at various distance scales over the rock outcrops in the seamounts. However, their variation patterns and controlling factors are not well understood. We conducted a comprehensive small-scale survey, including shipboard acoustic measurements, seafloor observations, and rock drilling over the Xufu Guyot of the Marcus-Wake seamounts in the Northwestern Pacific to characterize the thickness variations on a scale of several kilometers with the topography and geological evolution of the guyot. Rock drilling revealed that thicker CRC (>100 mm) tend to occur on the margins and flat areas on the guyot, while thinner CRC are associated with carbonate reef mounds over the volcanic pinnacles and seamount slopes. The microstratigraphic description indicated that the CRC thickness is strongly related to the geological evolution of the guyot, mainly the stability of the substrate rocks and coverage with calcareous pelagic sedimentation.

Novel hydrometallurgical process for the recovery of copper from end-of-life mobile phone printed circuit boards using ionic liquids

Printed circuit boards, which are embedded in mobile phones, are complex composite materials containing valuable components of strategic and critical importance. With the number of mobile phone devices operating worldwide expected to reach 18bn by 2025, their low recycling rate leads to high tonnages of waste printed circuit boards (WPCBs) at their end of life. Copper, representing 58% of the total metal content in an end-of-life mobile phone (EoL-MP) and the main metal present in the printed circuit board, with an average of 27.8 wt %, offers a resource-rich source of this strategic metal for recovery. To overcome the limitations associated with conventional technologies for recycling WPCBs, use of greener technologies (ionic liquids (ILs) as leaching agents), offers greater potential for the recovery of copper from this waste stream. Presented here for the first time is an optimised hydrometallurgical process for recovery of copper involving pre-treatment, leaching, and electrowinning and the use of two task-specific ionic liquids. The pre-treatment step, using the IL [Bmim]BF4 proved to be a clean, efficient, and non-polluting system for the separation of solder and electronic components (ECs) from WPCBs, at 210 °C, 150 rpm for 15 min, favouring the enrichment of copper for a subsequent recovery process. The IL, [Bmim]HSO4, successfully leaches >99% of copper from pretreated WPCBs under the optimal conditions of 30 %v/v [Bmim]HSO4, 10 %v/v H2O2, and 60 %v/v H2O at 60 °C, 1:15 solid to liquid ratio for 2 h. Recovery of copper is achieved through direct electrowinning from the [Bmim]HSO4-leach solution, as electrolyte. Under controlled deposition conditions of 100 mA (4.2 V) during 2 h, 100% of copper (>99% purity) is recovered with an average current efficiency of 78% and an energy consumption of 4.5 kWh/kg Cu. This work combines a dual leaching and electrowinning system that is clean, environmentally friendly, minimises reagent use and spent wastes, permits multiple reuses of both the ILs, and maximises resource conservation through recovery of copper metal and return of secondary streams (electronic components and solder) for reuse in new or refurbished components or products.

Extraction of Germanium from Low-Grade Germanium-Bearing Lignite by Reductive Volatilization.

Germanium (Ge) as an important strategic metal is widely used in many modern-technology fields such as optical fiber and thermal solar cells. In this study, the volatilization behavior of Ge from low-grade germanium-bearing lignite was investigated in detail through reductive volatilization. The results indicated that temperature and air flow rate in the semi-closed roasting system played a significant role in the process. The optimal volitation efficiency of Ge reached 98% at 1100 °C for 2 h with air flow rate of 0.7 L/min in a maffle furnace, respectively. Under optimal conditions, the contents of Ge lowered to 30 ppm in the roasting residue. Analysis of the enriched ash yielded 71,600 ppm for Ge. Chemical phase analysis of the Ge in the enrichment ash showed that soluble Ge accounted for 82.18% of the total Ge, which could be viewed as an excellent material for Ge extraction by chlorinated distillation.

Hydrochemistry, Elements Distribution and Their Potential Recoveries in Gold Metallurgical Treatment Tailings Dams

Wastewaters are valuable sources of metals and metalloids and can serve as essential resources for their recovery. Characterizing and understanding the occurrence of metals and other compounds, along with identifying the most effective recovery methods, are key steps in unlocking the potential for reusing these resources. The present study focused on analyzing waters from various mining dams in the Iron Quadrangle (IQ) region of Brazil, which contained metals such as Au, Cu, Ni, Zn, and sulfates resulting from the metallurgical treatment of Au. The results revealed a range of metal concentrations in the neutral zone in three tailings. Additionally, a 3D map was created, and a statistical analysis and an exploration of the processes governing mobility and partitioning were conducted to assess the potential for reuse. Notably, the study identified a high potential for Au recovery, particularly through the utilization of sustainable and cost-effective methods such as nanofibers with biosorbents. Overall, this research contributes to the understanding and exploration of potential reuse procedures for strategic metals in various industrial applications.

Critical and strategic metals in mobile phones: A detailed characterisation of multigenerational waste mobile phones and the economic drivers for recovery of metal value

Mobile phones have a high embedded value of interest within a circular economy. With the number of these devices operating worldwide expected to reach 18bn by 2025 their low recycling rate leads to large tonnages of End-of-Life Mobile Phones (EoL-MPs) and de facto a challenging waste stream. The rapid replacement of mobile phones to meet consumer demand further compounds the challenges due to increased demand for raw materials, increased energy, and water consumption, and, where uncontrolled and poor disposal at end-of-life occurs, significant impacts on health and the environment.EoL-MPs comprise a complex and heterogeneous combination of materials that include strategically and economically important high technology metals, many of which are classified as critical by the EU. A detailed characterisation of key components (PCBs, casings, screens, cameras, and speakers) of multigenerational (feature phones, multimedia phones, and smartphones) EoL-MPs is studied to determine the potential for recovery of both metal and non-metallic fractions and the economic drivers for recovery of the metal value. On average, the major mass fraction distributed in a mobile phone is: plastics (40%), metals (35%) and ceramics (25%).The results show that 1 tonne of EoL-MPs can contain up to 53 Kg copper, 141 g gold, 270 g silver, 10 g platinum, 18 g palladium and 3.3 Kg rare earth elements, among other valuable metals, with many of these elements found to be at least twice, and in some cases, up to 600 times more concentrated than in their natural ores. The calculated economic value of the EoL-MPs components is in the order: cameras (86,860 US$/ton), printed circuit boards (55,459 US$/ton), speakers (21,853 US$/ton) and screens (3,779 US$/ton). Based on the predicted 5 billion EoL-MPs discarded by the end of 2022, this waste stream has a potential economic value of US$ 9.25 billion. Use of EoL-MPs as a secondary resource-rich stream of these critical materials therefore offers a route to close the materials loop, helps to mitigate the threat to natural resources and the environmental and human health impacts arising from mining operations, relieves supply demands and contributes to the economy.

Uncovering the features of global antimony resource trade network

Antimony is a scarce strategic metal and plays an extremely important role in the modern societies. Due to the increasing demands for various antimony-containing products, it is critical to identify the key supply risk of antimony industrial chain. This study aims to uncover the key features of antimony-related trade flows from a global value chain perspective and assess the trade network linkage and features of global antimony resource by using a complex network model and a stochastic block model. Also, the trade network evolution of global antimony resources is investigated by using an exponential random graph expansion method so that valuable policy insights can be obtained for preparing appropriate policies to facilitate sustainable antimony resource management. Results show that the network structure of the global antimony resource presents a significant center-periphery feature. China, India, Vietnam and Tajikistan have always acted as trade intermediaries and bridges of global antimony resources. Also, the evolution of global antimony resources trade network was driven by trade network autonomy and exogenous network embeddedness. In addition, geopolitics is the biggest obstacle to maintain the operation of this global antimony trade network. Finally, policy recommendations are proposed to help ensure sustainable supply of antimony resources.

Effect of V2O5 on Consolidation, Reduction, and Softening-Melting Behavior of High-Cr Vanadium Titanomagnetite

Vanadium titanomagnetite is an important mineral resource. It is a raw material for ironmaking, vanadium extraction, strategic metal titanium production, and titanium dioxide production. In this study, high chromium vanadium titanomagnetite (High-Cr VTM) and ordinary iron ore were used as raw materials for pelletizing. The effect of V2O5 on the preparation and properties of High-Cr VTM pellets was studied. The influence of V2O5 on the properties of the green pellets, the compressive strength of oxidized pellets, the reduction swelling index and reduction degree, softening-melting behavior, and the migration law of Fe, Ti, and Cr in the reduction process were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that with the increase in V2O5 content, the properties of the green pellets basically showed a trend of first decreasing and then increasing but all met the basic requirements of pelletizing. When the added amount of V2O5 in the pellet was 6%, the compressive strength of the oxidized pellet was the lowest at only 2565 N/pellet but it still met the quality requirements for pellets in blast furnace production. As the dosage of V2O5 increased, the reduction swelling index and reduction degree of the pellets showed a trend of first increasing and then decreasing. The addition of V2O5 can increase the softening initial temperature, softening final temperature, melting start temperature, and dripping temperature of the High-Cr VTM pellets, narrowing the softening interval, and expanding the melting dripping interval. The experimental results provided a data reference for revealing the influence of V2O5 on High-Cr VTM pellets during the blast furnace smelting process.

Complexation leaching of critical and strategic metals from nickel converter slag using organic acids

Nickel converter slag is a waste product formed during the converting process in nickel production. In recent times the processing of nickel converter slag has gained attention as a secondary source of cobalt (Co) and nickel (Ni). Nickel and cobalt are considered critical and strategic metals that are essential for nations’ economy and defence, as well as high-technology industry. In particular, Co and Ni can be utilised in the batteries, superalloys, and automobiles. Extraction of critical and strategic metals from slag can be categorised as technospheric mining. In this study, the slag was characterised using combination of XRF, XRD, ICP-OES, FESEM and TIMA for better understanding of deportment of Ni and Co and texture of Ni converter (CV) slag. Complexation leaching by using a combination of citric acid and EDTA was undertaken to extraction by using the leaching agent and complexing agent. The preliminary test showed the most promising result. The leaching experiment was carried out with various parameters such as the reagent concentration, temperature, particle size, and pulp density. The optimum condition for extracting Co and Ni from CV slag is following; citric acid 1 M, EDTA 0.3 M, 80 °C, 6 hr, pulp density 2.5% (w/v), − 75 μm and 250 rpm, which recovered 85.29% of Co and 59.85% of Ni.