Extraction Of Platinum Group Metals Research Articles

NEW TECHNOLOGIES FOR PROCESSING TAILINGS OF A COPPER PROCESSING PLANT FOR THE EXTRACTION OF PLATINOIDS

The most important task of the mining and metallurgical industry in the world is the development of technology for the processing of industrial waste from metallurgical industries. In the world, balance ores of precious metals are practically available. This issue develops the processing of man-made waste, refractory ores, off-balance and low-grade dumps. The article considers studies of the material and rational compositions of the tailings of a copper concentrating plant in the conditions of JSC Almalyk MMC, determines the optimal method for tailings enrichment with an increase in the content of precious metals in the concentrate, and enhances an unconventional new scheme for processing platinum group concentrates with the extraction of platinum, palladium, silver and high recovery gold. Based on the learned subjects and analysis of studies results, the authors concluded that the centrifugal concentration of platinoids from the composition of the tailings was achieved due to accurate determinations of the particle size in the tailings with the selection of intense gravity modes. Combined hydrometallurgical methods for purifying platinoids and gold from impurities using combinations of chemical solvents have been developed. As a result, the developed technologies have achieved the possibility of complex extraction of platinum group metals from the tailings of concentrating plants of copper production with high degrees, through extraction of all precious metals.

NEW TECHNOLOGIES FOR PROCESSING TAILINGS OF A COPPER PROCESSING PLANT FOR THE EXTRACTION OF PLATINOIDS

The most important task of the mining and metallurgical industry in the world is the development of technology for the processing of industrial waste from metallurgical industries. In the world, balance ores of precious metals are practically available. This issue develops the processing of man-made waste, refractory ores, off-balance and low-grade dumps. The article considers studies of the material and rational compositions of the tailings of a copper concentrating plant in the conditions of JSC Almalyk MMC, determines the optimal method for tailings enrichment with an increase in the content of precious metals in the concentrate, and enhances an unconventional new scheme for processing platinum group concentrates with the extraction of platinum, palladium, silver and high recovery gold. Based on the learned subjects and analysis of studies results, the authors concluded that the centrifugal concentration of platinoids from the composition of the tailings was achieved due to accurate determinations of the particle size in the tailings with the selection of intense gravity modes. Combined hydrometallurgical methods for purifying platinoids and gold from impurities using combinations of chemical solvents have been developed. As a result, the developed technologies have achieved the possibility of complex extraction of platinum group metals from the tailings of concentrating plants of copper production with high degrees, through extraction of all precious metals.

Platinum Group Metals Extraction from Asteroids vs Earth: An Overview of the Industrial Ecosystems, Technologies and Risks

Platinum Group Metals Extraction from Asteroids vs Earth: An Overview of the Industrial Ecosystems, Technologies and Risks

Optimized Bioleaching Pre-treatment of UG-2 PGM Flotation Concentrate Using Design of Experiments

AbstractThe depletion of the Merensky ore has led the South African platinum industry into largely mining and processing Upper Group Two (UG-2) ore for the extraction of Platinum Group Metals (PGMs). However, the processing of the UG-2 material is not fully amenable to the conventional pyrometallurgical route due to the high chrome content. Therefore, in this study, a bio-based process for base metal extraction from UG-2 flotation concentrates was investigated. This study represents only part of the work done in a broader investigation to develop a completely biological two-stage process for the extraction of base metals and PGEs. In this paper, only the first stage of the process is presented. This study evaluated a mixture of indigenous thermoacidophile archaebacteria namely, Acidianus brierleyi, Sulfolobus sp., and Metallosphaera sedula. A statistical Design of Experiments (DOE) was used for finding optimal conditions. Factors investigated included particle size, pH, pulp density, inoculum dosage, and temperature. Optimal extraction efficiencies of 92% for Co, 97% for Cu, and 99% for Ni were predicted at correlation coefficients of 92.5%, 93.2%, and 88.0%, respectively, thus, verifying the fitness of the model. Optimal base metal extractions obtained were 99.3% for Co, 90.1% for Cu, 41.58% for Fe, and 99.5% for Ni. The results showed a substantial extraction of base metals from UG-2 PGM flotation concentrate suggesting a potentially feasible option for industrial bioprocessing of PGM concentrates. To the best of the authors’ knowledge, this is the first report on bioleaching of base metals from UG-2 flotation concentrates. Graphical Abstract

Extraction of PGMs from insoluble Fe-Si-PGMs alloy by combined thermochemical and mechanochemical leaching: Sustainable, efficient, and scalable

Platinum group metals (PGMs) are scarce critical materials, and recovering PGMs from spent automotive catalysts (SAC) is economically and ecologically important. However, dissolving the Fe-Si-PGMs alloy derived from SAC is challenging, impeding PGMs recovery. This study aims to develop a more sustainable, efficient, and scalable leaching scheme. We demonstrate efficient leaching of Fe-Si-PGMs alloy using a thermochemical combined with mechanochemical leaching method with a HCl + FeCl3 + H2O2 solution. Kinetics parameters studies optimize the leaching process. The main obstacles to leaching are the chemical inertness of the alloy and the SiO2 encapsulation formed. Ultimately, efficient dissolution of 99 % Pd, 95 % Pt and 88 % Rh was achieved, increasing PGMs leaching by 17 % compared to single thermochemical leaching. Additionally, this work remedies the scalability limitations of mechanochemical leaching and provides valuable insights for PGMs recovery.

Efficient HCl leaching of platinum group metals from waste three-way catalysts: A study on kinetics and mechanisms

Waste three-way catalysts (TWCs) have attracted much attention due to the presence of platinum group metals (PGMs) and hazardous substances such as heavy metals and organic matter. The extraction of PGMs from waste TWCs using hydrochloric acid (HCl) has been extensively researched. However, the addition of oxidizing agents like H2O2 and aqua regia is necessary to facilitate PGMs dissolution, which poses significant environmental and operational hazards. Hence, developing a green PGMs recovery process without oxidants is imperative. Previously, we investigated the process of Li2CO3 calcination pretreatment to enhance the leaching of PGMs from waste TWCs by HCl, focusing on the process and mechanism of Li2CO3 calcination pretreatment. In this study, we focused on the leaching process of HCl after pretreatment. Our investigation includes a detailed examination of leaching kinetics and mechanisms. The optimal leaching conditions were: leaching temperature of 150 °C, leaching time of 2 h, HCl concentration of 12 M, and liquid-solid ratio of 10 mL/g. The experiments resulted in maximum leaching rates of about 96%, 97%, and 97% for Pt, Pd, and Rh, respectively. However, given the presence of heavy metals, attention needs to be paid to the harmless treatment of waste acids and leaching residues. The Pt and Pd leaching process is controlled by a mixture of interfacial chemical reactions and internal diffusion, and dominated by internal diffusion, while the leaching process of Rh is controlled by interfacial chemical reactions. Li+ in Li2PtO3, Li2PdO2, and Li2RhO3 preferentially leached and underwent ion-exchange reactions with H+, promoting the dissolution of Pt, Pd, and Rh in HCl.

Bioleaching of the α-alumina layer of spent three-way catalysts as a pretreatment for the recovery of platinum group metals

Acid bioleaching of Al by Acidithiobacillus thiooxidans has been explored as an environmentally friendly pretreatment to facilitate the extraction of platinum group metals from spent three-way catalysts (TWC). Biogenic sulfur obtained from desulfurization bioreactors improved the production of acid by A. thiooxidans compared to commercially available elemental sulfur. The lixiviation abilities of bacteria-free biogenic acid and biogenic acid with exponential or stationary phase bacteria were compared against a control batch produced by commercial H2SO4. The maximum Al leaching percentage (54.5%) was achieved using biogenic acids with stationary-phase bacteria at a TWC pulp density of 5% w/v whereas bacteria-free biogenic acid (23.4%), biogenic acid with exponential phase bacteria (21.7%) and commercial H2SO4 (24.7%) showed lower leaching abilities. The effect of different pulp densities of ground TWC (5, 30, and 60% w/v) on Al leaching and bacterial growth was determined. While greater Al leaching yields were obtained at lower TWC pulp density solutions (54.5% at 5% w/v and 2.5% at 60% w/v), higher pulp densities enhanced microbial growth (2.3 × 109 cells/mL at 5% w/v and 9.5 × 1010 cells/mL at 60% w/v). The dissolution of the metal from the solid into the liquid phase triggered the production of biological polymeric substances that were able to absorb traces of both Al (up to 24.80% at 5% w/v) and Pt (up to 0.40% at 60% w/v).

Recovery of platinum group metals from aqueous solution by iron-electrocoagulation

The recovery of platinum group-metals (PGMs) has attracted increasing attention owing to their scarcity, economic importance, and criticality. Traditional techniques for PGM recovery often involve the use of toxic reagents and require strict extraction conditions, posing challenges for their implementation in complex environments. In this paper, a novel method based on iron electrocoagulation (Fe-EC) is proposed for PGM extraction. The Fe-EC process generates iron (hydr)oxide flocs in situ, which spontaneously and uniformly adsorb and reduce PGM ions. The selectivity of PGM recovery is attributed to the higher electronegativity and standard reduction potential of PGM ions compared to base metal ions. Efficient extraction of Pt, Pd, and Rh ions from aqueous solutions was achieved using Fe-EC, with extraction efficiencies of 81.26 %, 81.32 %, and 99.66 %, respectively. These results were obtained at a voltage of 2 V and residual concentrations of 0.3072, 0.0051 and 0.0049 mg L–1. TEM-EDS and XPS characterizations of the Fe-EC flocs showed that Pt, Pd, and Rh were present in the elemental form particles. The extraction performance of base metal such as Ni, Zn, Mg and Mn ions by Fe-EC was found to be poor, with minimal reduction to elemental form. Finally, the Fe-EC flocs were subjected to acid washing and filtration, resulting in the selective recovery of Pt, Pd, and Rh products with high purities of 97.43%, 97.12%, and 97.92%, respectively. This study presents a new and environmentally friendly method for the recycling of PGMs, offering a promising approach for sustainable PGM recovery.

Failure analysis of three-way catalysts through comprehensive characterization and understanding the role of pretreatment

Currently, most of the studies on waste three-way catalysts (TWCs) have focused on the extraction of platinum group metals (PGMs), with less characterization and analysis of their properties. This can lead to an incomplete understanding of the physicochemical properties and causes of failure of waste TWCs, which in turn affects the recovery of PGMs. This paper conducted various characterization analyses on waste TWCs, including their chemical composition, particle size, surface elements, microscopic morphology, specific surface area, and thermal stability. The PGMs content in the waste TWCs is 1468 g/t, and the total content of rare earth elements is about 1.58%, which has high recovery value. The analysis identified several reasons for TWC failure: the presence of S and P elements caused sulfidation and phosphorylation poisoning of PGMs; PGMs were also partially oxidized to PtO2, PdO2 and Rh2O3; in addition, sintering and agglomeration of waste TWC powder, encapsulation of PGMs in the substrate, reduction of specific surface area and total pore volume, and adsorption of accumulated carbon were also considered as causes of failure. The physicochemical properties of waste TWCs are extremely important for the selection of the PGM extraction process among them. Therefore, the effects of several pretreatment methods on the leaching efficiency of PGM were investigated. The results showed that grinding reduced the leaching rate of PGMs, and HCOOH reduction and NaHSO4 calcination pretreatment could improve the leaching rate of Pt and Rh, respectively; while the Li2CO3 calcination pretreatment could result in 70.87% leaching of Pt directly in HCl. The feasibility of extracting PGMs from waste TWCs using a Li2CO3 calcination pretreatment followed by direct HCl leaching was validated.

Review: Extraction of platinum group metals from catalytic converters

Platinum group metals (PGM) are widely used in catalytic industry due to their outstanding physical and chemical properties (high-temperature stability, high catalyst activity, high heat resistance, high corrosion resistances). They are used in medical fields, electronics, oil refining, production of ammonia, fuel cells, automotive industry. Catalytic wastes are an important secondary source of metals because recycling of wastes is more economical and ecological way of metals obtaining compared to mining from ores. Spent automotive catalyst is a rich source of platinum group metals [PGM: platinum (Pt), palladium (Pd), and rhodium (Rh)] which contains higher concentrations of PGM than found in natural ores. This review presents the analysis of the recovery methods of platinum group metals from spent catalysts and their advantages and disadvantages. As a result, all methods were analyzed and the most promising (most environmentally friendly and economical) was pointed out.

Обзор: Извлечение металлов платиновой группы из каталитических конвертеров

Металлы платиновой группы (PGM) широко используются в каталитической промышленности благодаря своим выдающимся физико-химическим свойствам (высокотемпературная стабильность, высокая каталитическая активность). Они используются в медицине, электронике, нефтепереработке, производстве аммиака, топливных элементов, автомобилестроении и т.д. Каталитические отходы являются важным вторичным источником металлов, поскольку переработка отходов является более экономичным и экологичным способом получения металлов по сравнению с добычей из руд. Отработанный автомобильный катализатор является богатым источником металлов платиновой группы [PGM: платина (Pt), палладий (Pd) и родий (Rh)], которые содержат более высокие концентрации PGM, чем в природных рудах. В данной статье представлен критический обзор состояния методов извлечения металлов платиновой группы из утилизированных катализаторов, их преимуществ и недостатков. В результате были проанализированы все методы и выделены наиболее перспективные (наиболее экологичные и экономичные).

Understanding the distribution of platinum group metals and gold in the process of copper-nickel slag depletion with gas mixtures

This paper describes the results of a study that looked at the distribution of platinum group metals (PGMs) (Pt, Pd, Rh, Ru, Ir) and Au between Cu – Ni – Fe bottom phase and dump slag as a result of pyrometallurgical depletion of slag, a by-product of oxidizing smelting of sulphide copper-nickel concentrate. The pyrometallurgical process was performed in a bubbling mode using reducing gas mixtures of various compositions. The consumption of reducing agent was found to be the key factor governing the output of the bottom phase and hence the chemical composition of the products. For the first time ever, the authors used the results of the chemical analysis of the products to calculate the distribution coefficients for PGMs and gold between the bottom phase versus the slag when the depletion process involved an intensive stirring of the melt. Thus, a variation range was established for the distribution coefficients of noble metals, as well as the threshold concentration of Fe in the melt. Once the latter has been reached, the distribution coefficients remain almost unchanged and the extraction of PGMs into dump slag is minimal. Using scanning electron microscopy and electron probe microanalysis, the authors established how many noble metals get carried away with dump slag. Proneness of Au to get dissolved in silicate melts was revealed, which is also typical of Cu. The conducted study helped establish that only 5% of Pt, Pd and Rh gets carried away with dump slag, which is the least loss. At the same time, about 10% of Ru and Ir goes into dump slag. The data reflecting the behavior of Au during slag depletion with reducing gas mixtures confirm that the maximum recovery of this metal from the slag would only be possible under a high reduction potential of the system. This corresponds to the minimum concentration of Fe in the bottom phase of 50% wt.

New directions processing of technogenic waste of the copper industry

At the present time, in the mining and metallurgical industry there are trends in the processing of man-made waste that have accumulated over the course of many years. Since the world’s reserves of ore deposits with a high initial content of non-ferrous metals and easily processed ores are currently practically depleted. This is due to a decrease in the volume of processing of conditioned ores and the involvement in the development of industrial waste, refractory ores and off-balance from low-grade dumps. High prices for metals on the world market create a favorable environment for the development of technologies for the extraction of precious metals involving the processing of mineral resources of technogenic origin. The work studies the mineralogical composition of industrial waste from the copper industry in the conditions of JSC “Almalyk MMC”, determined the effectiveness of methods for the selective extraction of platinoids and paid attention to the methods of dissolution, reduction of platinum metals and methods of their purification from various impurities. Based on the study of this topic and the analysis of the results of the research, the authors proposed an optimal technology and complex methods for extracting platinum, palladium and rhodium from industrial waste using selective methods suitable for each metal separately using hydrometallurgy and pyrometallurgy. Hydrometallurgical methods have been developed for the purification of palladium, platinum and rhodium with treatment, respectively, with formic, citric and nitric acids. As a result of the developed technologies, the possibility of complex extraction of platinum group metals from industrial waste has been achieved. In this case, the end-to-end extraction of all platinoids is over 80 %.

NEW HORIZONS PROCESSING OF TECHNOGENIC WASTE OF THE COPPER INDUSTRY

At the present time, in the mining and metallurgical industry, there are trends in the processing of man-made waste that have accumulated over the course of many years. Since the world's reserves of ore deposits with a high initial content of non-ferrous metals and easily processed ores are currently practically depleted. This is due to a decrease in the volume of processing of conditioned ores and the involvement in the development of industrial waste, refractory ores and off-balance from low-grade dumps. High prices for metals on the world market create a favorable environment for the development of technologies for the extraction of precious metals involving the processing of mineral resources of technogenic origin. The work studies the mineralogical composition of industrial waste from the copper industry in the conditions of JSC "Almalyk MMC", determined the effectiveness of methods for the selective extraction of platinoids and paid attention to the methods of dissolution, reduction of platinum metals and methods of their purification from various impurities. Based on the study of this topic and the analysis of the results of the research, the authors proposed an optimal technology and complex methods for extracting platinum, palladium and rhodium from industrial waste using selective methods suitable for each metal separately using hydrometallurgy and pyrometallurgy. Hydrometallurgical methods have been developed for the purification of palladium, platinum and rhodium with treatment, respectively, with formic, citric and nitric acids. As a result of the developed technologies, the possibility of complex extraction of platinum group metals from industrial waste has been achieved. In this case, the end-to-end extraction of all platinoids is over 80%.

Bioleaching of platinum, palladium, and rhodium from spent automotive catalyst using bacterial cyanogenesis

Bioleaching of platinum group metals (PGM) from spent automotive catalyst (SAC) was studied using two mesophiles, Pseudomonas fluorescens and Bacillus megaterium. Leaching studies under different conditions were carried out to investigate the formation of biocyanide and its role in PGM solubilisation. Both P. fluorescens and B. megaterium produce cyanide as a secondary metabolite that forms water-soluble complexes with PGM. Factors that affect bioleaching, namely initial pH of culture, free cyanide ion concentration, and pulp density were examined. Two leaching strategies - two-step bioleaching and spent medium leaching were applied. P. fluorescens showed higher extraction compared to B. megaterium. Using spent medium leaching for pretreated SAC at 0.5% (w/v) pulp density and initial pH 10, P. fluorescens yielded the highest extraction of platinum (58%), palladium (65%) and rhodium (97%) on day 1. This study demonstrates the bioleaching potential of cyanogenic bacteria for the extraction of PGM from SAC.

Extraction of Platinum Group Metals and Gold from Industrial Environments into Deep Eutectic Solvents

Extraction of Platinum Group Metals and Gold from Industrial Environments into Deep Eutectic Solvents

Extraction behavior of a novel functionalized ionic liquid for separation of platinum group metals from aqueous nitric acid solution.

A novel ionic liquid (IL) functionalized with thiodiglycol amic acid containing a soft S donor was synthesized for the effective and efficient extraction of platinum group metals (Ru, Rh, and Pd) from aqueous nitric acid solutions, such as high-level radioactive liquid waste (HLLW). The IL enabled rapid extraction of Pd(II) with an extraction ratio of approximately 100%. The extractions of Ru(III) and Rh(III) by the IL were slower than that of Pd(II), but the rates were accelerated by temperature elevation. The extractions of Ru(III) and Rh(III) at 50°C reached equilibrium within 4 and 8h, respectively, with the extraction ratios of over 90% without assisting agents or other methods for the extraction system. Furthermore, the IL could extract more than 90% of Ru(III), Rh(III), and Pd(II) from the simulated HLLW within 2h at 50°C.

Recovery of platinum group metals from spent automotive converters by leaching with organic and inorganic acids and extraction with quaternary phosphonium salts

The paper presents studies on the application of hydrometallurgical recovery of platinum group metals (PGM) from spent automotive converters (SAC), which is not only commercially viable but also important from an ecological perspective. The work proposes an integrated four-stage process, which includes: leaching with oxalic or lactic acids, then leaching with mineral acids from catalyst left after the first stage and next extraction of PGM with phosphonium or ammonium salts: Cyphos IL 101 (trihexyl(tetradecyl)phosphonium chloride), Cyphos IL 104 (trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate), and in the final stage, stripping with 0.1 M thiourea in 0.5 M HCl and 3 M HNO3 to recover PGM. The use of carboxylic acids in the first step of leaching reduces the amount of non-precious metals (Fe ions, Mg(II), Zn(II)) leached in the second stage. The highest concentration of the leached Al(III), Fe ions, Mg(II) and Zn(II) was 600, 25, 110 and 45 mg/dm3. To leach PGM from SAC, it was necessary to use stronger acidic solutions (e.g. a mixture of inorganic acids with an oxidant). The concentrations of Pt(IV), Pd(II), Rh(III) in the solutions after the second step of leaching were 34–40, about 3, 4.5–5 mg/dm3, respectively. After two stages of extraction, Rh(III) and Al(III) are left in the raffinate, therefore Pt(IV) and Pd(II) can be separated from Rh(III). Afterward, Pd(II) and Pt(IV) extracted to the organic phases can be separated in the first stage of stripping.

Complexation-Distribution Separated Solvent Extraction Process Designed for Rapid and Efficient Recovery of Inert Platinum Group Metals.

Previously, we have demonstrated that thermal-assisted techniques can accelerate the extraction of inert platinum group metals (PGMs), while they still have several concerns about difficulty of temperature control in actual extraction contactors and safety risks arising from heating organic solvents. In this study, we report a complexation–distribution separated extraction process for the accelerated extraction of inert PGMs. This extraction method includes two steps: (1) complexation of PGMs with extractants in aqueous solution and (2) distribution of the formed complex from the aqueous phase to organic one. We separately investigated the complexation and distribution processes for typical inert PGMs such as Ru(III) and Rh(III) in the presence of water-soluble N,N,N′,N′-tetra-alkylpyridinediamide ligands (PDA) and bis(trifluoromethylsulfonyl)amide (Tf2N–) counteranions. As a result, the water-soluble complexes of Ru(III) and Rh(III) with PDA can be formed in 0.5 M HNO3(aq) within 3 h under heating at 356 K. The formed complexes were extracted to the 1-octanol layer containing Tf2N– within 5 min at room temperature, where this hydrophobic anion plays an important role to promote extraction of PGMs as an anionic phase-transfer catalyst (PTC). Consequently, we successfully established and demonstrated the complexation–distribution separated extraction process for the accelerated extraction of inert PGMs using a water-soluble ligand and anionic PTC.

Recovery of Palladium(II) and Platinum(IV) in Novel Extraction Systems.

Recovery of platinum group metals (PGM) from complex aqueous solutions generated as a result of leaching of various spent materials (e.g., spent automotive converters) is a vital issue in the context of the circular economy. In this study pyridinium derivatives containing an imidoamide or imine moiety (i.e., 3-[1-(2-ethylhexyloxyimine)methane]-1-propylpyridinium chloride, 3-[1-(decyloxyimine)methane]-1-propylpyridinium chloride, 3-[1-(decyloxyimine)ethane]-1-propylpyridinium chloride and 4-[1-amine(2-ethylhexyloxyimine)]-1-propylpyridinium chloride) are proposed as novel extractants for recovery of palladium(II) and platinum(IV) from model chloride aqueous solutions. The results of liquid-liquid extraction from one-component solutions of palladium(II) or platinum(IV) showed that quaternary pyridinium salts can be used as effective extractants for platinum metal ions. Moreover, PGM extraction from a two-component mixture proved no evident selectivity in the transfer of one of the metal ions to the organic phase. As the best extractant among the investigated ones, D3EI-PrCl (with straight alkyl chain at substituent) can be pointed out, however, problems with effective stripping or phase disengagement after stripping should be indicated as a drawback of the organic phases used. Further investigation should focus on the improvement of the organic phase properties (e.g., increase in hydrophobicity of the extractants and addition of an organic phase modifier) towards stripping efficiency.