Recovery Of Platinum Group Metals Research Articles

Membrane Electrode Assembly (MEA) Recycling

Due to the climate change and other environmental aspects linked to the use of fossil fuels, renewable energy and clean technologies such as hydrogen/oxygen fuel cells have gained renewed interest in the last decades. However, fuel cell manufacture and management of spent fuel cells could also represent a significant impact on the environment. Several studies to assess the extent of this impact were carried out using life cycle analysis (LCA) [1-6], concluding that the membrane electrode assembly (MEA) is the component that contributes the most to the overall environmental impact, mainly due to the extraction of platinum group metals (PGM), which are the main contributor to the acidification burden of MEA manufacture. These studies also affirm that important reductions in pollution can be achieved if the MEA materials are recycled. The recovery of the PGM can be achieved through thermal, chemical or biological methods [7,8]. All of these methods present benefits and drawbacks. For example, thermal treatments are not an environmentally friendly option when recycling most commonly used MEAs, since the Nafion membrane generates acids in the combustion. On the other hand, although biological recovery of PGM is the most environmentally preferable process, there is lack of studies on the integration of this step with the MEA recycling process. The recovery of PGM or membrane materials from MEAs using chemical methods is well documented. Nonetheless, very few studies seem to propose a method to recover both the catalyst and the membrane at the same time, even though the membrane material highly contributes to the final MEA cost. This work proposes a new recycling method of MEAs from hydrogen-oxygen fuel cells, where all main components like the Nafion membrane, carbon powder and metallic platinum were recovered through chemical methods. [1] M. Pehnt, “Life-cycle analysis of fuel cell system components,” Handb. Fuel Cells – Fundam. Technol. Appl., vol. 4, pp. 1293–1317, 2003. [2] M. Miotti, J. Hofer and C. Bauer, “Integrated environmental and economic assessment of current and future fuel cell vehicles,” Int. J. Life Cycle Assess., pp. 1–17, 2015. [3] A. Simons and C. Bauer, “A life-cycle perspective on automotive fuel cells,” Appl. Energy, vol. 157, pp. 884–896, 2015. [4] S. R. Dhanushkodi, N. Mahinpey, A. Srinivasan and M. Wilson, “Life cycle analysis of fuel cell technology,” J. Environ. Informatics, vol. 11, no. 1, pp. 36–44, 2008. [5] D. A. Notter, K. Kouravelou, T. Karachalios, M. K. Daletou, and N. T. Haberland, “Life cycle assessment of PEM FC applications: electric mobility and μ-CHP,” Energy Environ. Sci., vol. 8, pp. 1969–1985, 2015. [6] D. Garraín and Y. Lechón, “Exploratory environmental impact assessment of the manufacturing and disposal stages of a new PEM fuel cell,” Int. J. Hydrogen Energy, vol. 39, pp. 1769–1774, 2014. [7] H. Dong, J. Zhao, J. Chen, Y. Wu, and B. Li, “Recovery of platinum group metals from spent catalysts: A review,” Int. J. Miner. Process., 2015. [8] M. A. Barakat and M. H. H. Mahmoud, “Recovery of platinum from spent catalyst,” Hydrometallurgy, 2004. Figure 1

Effect of different grinding media composition on the flotation of a PGM ore

In the present study, the effect of using different grinding media, viz, ceramic (CE), forged steel (FS), 15% Cr steel (CS), stainless steel (SS) and a mixture of stainless steel and 15% Cr steel balls (50:50) (SS + CS) were investigated using a Platinum Group Metal (PGM) ore, UG2. Test work was conducted using a laboratory scale horizontal tumbling mill and a batch flotation cell. Power draw to achieve a specific P80 was determined for each media type. The different flotation behaviour obtained from different media is discussed in terms of particle size distribution, water recovery, solid recovery and valuable mineral recovery. pH, Redox potential (Eh) and dissolved oxygen (DO) level were also measured. Grinding products of five different media produced the same solids and water recovery, but the grades and recoveries of PGM and chromite were different. Grinding products of ceramic media had the best flotation performance, which produced the highest PGM recovery and the lowest Cr2O3 recovery. Meanwhile grinding products of stainless steel balls (SS) produced the lowest PGM recovery and highest Cr2O3 grade and recovery in the concentrates. The paper proposes possible reasons to explain these observations.

Recovery of Platinum Group Metals from Spent Catalysts Using Iron Chloride Vapor Treatment

The recovery of platinum group metals (PGMs) from spent automobile catalysts is a difficult process because of their relatively low contents in the scrap. In this study, to improve the efficiency of the existing recycling techniques, a novel physical concentration method involving treatment with FeCl2 vapor has been examined. The reactions occurring between typical catalyst components and FeCl2 vapor are discussed from the thermodynamic point of view, and the validity of the proposed technique was experimentally verified. The obtained results indicate that the vapor treatment at around 1200 K (927 °C) can effectively alloy PGMs (Pt, Pd, and Rh) with Fe, resulting in the formation of a ferromagnetic alloy. It was also confirmed that cordierite and alumina (the major catalyst components) remained unreacted after the vapor treatment, while ceria species were converted into oxychlorides. The samples simulating the automobile catalyst were also subjected to magnetic separation after the treatment with FeCl2 vapor; as a result, PGMs were successfully extracted and concentrated in the form of a magnetic powder. Thus, the FeCl2 vapor treatment followed by magnetic separation can be utilized for recovering PGMs directly from spent catalysts as an effective pretreatment for the currently used recycling methods.

Refining Approaches in the Platinum Group Metal Processing Value Chain—A Review

Mineable platinum group metal (PGM) deposits are rare and found in relatively few areas of the world. At the same time, the use of PGM is predicted to expand in green technology and energy applications, and PGMs are consequently currently listed as European Union critical metals. Increased mineralogical complexity, lower grade ores, and recent PGM production expansions give rise to the evaluation of the value chain of the capital-intensive conventional matte smelting treatment and other processing possibilities of the ore. This article will review the processes and value chain developed to treat ores for PGM recovery, highlighting hydrometallurgical refining approaches. It groups processes according to their rationale and discusses the special features of each group.

Potential Processing Routes for Recovery of Platinum Group Metals from Southern African Oxidized PGM Ores: A Review

The beneficiation of platinum group metals (PGMs) from pristine (unweathered) sulfide ores has conventionally been conducted through froth flotation, which typically achieves platinum recoveries of over 85%. The achieved successes of PGM concentration by flotation from the pristine sulfide ores are largely due to the occurrence of PGMs in close association with base metal sulfide minerals like chalcopyrite, pentlantite, and pyrrhotite which are easily floatable. However, the fast depletion of sulfide PGM-bearing minerals has triggered interest in exploring the recovery of the PGMs from near-surface oxidized PGM ores which have proven to be more difficult to process by conventional means as an alternative source to sustain production of PGMs. Earlier attempts to process the oxidized PGM ores by conventional flotation methods achieved poor recoveries (typically less than 50%). The resource estimates of oxidized PGM ores which are either unmined, mined, and stockpiled or discarded as overburden waste in South Africa and Zimbabwe are over 500 million tonnes. The economic benefits that could be realized in the event of an alternative and effective processing technique being developed would be immense. This paper reviews and discusses different research efforts that have been made to improve PGM recoveries from oxidized ores, and their merits and demerits.

A Comparative Life Cycle Assessment of Recycling the Platinum Group Metals from Automobile Catalytic Converter: An Australian Perspective

This study provides a comparison between environmental impacts of the recovery of platinum group metals (PGMs) from the end-of-life catalytic converters by hydrometallurgical and pyrometallurgical methods. A gate to grave life cycle assessment of a typical three-way catalytic converter manufactured for an Australian passenger car was carried out using GaBi professional environmental package. Recovery rates, as well as qualities, quantities, losses, and fugitive emissions for all materials and elements used in both methods were calculated based on the developed flowsheets. A life cycle impact assessment was then made by carrying out a mass balance calculation. Inventory data show that the hydrometallurgical route for recycling of the platinum group metals out of catalytic converter scrap has lower impacts on the environment compared with the pyrometallurgical method. In terms of emission effects, the hydrometallurgical process was found to be highly advantageous since it causes insignificant emissions to air, sea water, and fresh water. It is also found that the hydrometallurgical route performs comparatively superior in terms of acidification, eutrophication, fossil depletion, and human toxicity. The obtained results are applicable only to the Australian setting.

Pyrometallurgical Recovery of Platinum Group Metals from Spent Catalysts

As an important secondary resource with abundant platinum group metals (PGMs), spent catalysts demand recycling for both economic and environmental benefits. This article reviews the main pyrometallurgical processes for PGM recovery from spent catalysts. Existing processes, including smelting, vaporization, and sintering processes, are discussed based in part on a review of the physiochemical characteristics of PGMs in spent catalysts. The smelting technology, which produces a PGM-containing alloy, is significantly influenced by the addition of various collectors, such as lead, copper, iron, matte, or printed circuit board (PCB), considering their chemical affinities for PGMs. The vaporization process can recover PGMs in vapor form at low temperatures (250–700°C), but it suffers high corrosion and potential environmental and health risks as a result of involvement of the hazardous gases, mainly Cl2 and CO. The sintering process serves as a reforming means for recycling of the spent catalysts by in situ reduction of their oxidized PGMs components. Among these processes, the smelting process seems more promising although its overall performance can be further improved by seeking a suitable target-oriented collector and flux, together with proper pretreatment and process intensification using an external field.

Magnetic Concentration of Platinum Group Metals from Catalyst Scraps Using Iron Deposition Pretreatment

Spent automobile catalysts are the most important secondary source of platinum group metals (PGMs). However, effective recovery of PGMs from catalyst scraps is difficult because they are present in only small quantities as chemically stable substances. In this study, in order to improve the efficiency of the existing recycling processes, the authors experimentally investigated a novel physical concentration pretreatment process for PGMs using samples that simulate an automobile catalyst. In order to magnetically separate PGMs directly from the catalysts, ferromagnetic Fe was deposited on the PGM particles (or the porous catalyst layer) using an electroless plating technique. By using a plating bath containing sodium borohydride and potassium sodium tartrate as the reducing and complexing agents, respectively, Fe was successfully deposited on the sample without requiring complicated pretreatments such as sensitization and activation. After Fe deposition and subsequent pulverization, the PGMs could be extracted and concentrated in the form of magnetic powder using a magnet. The proposed magnetic concentration process was demonstrated to be feasible, and it has the potential to make the recycling of PGMs more efficient and environmentally friendly.

Application of immiscible magnetic liquids of different densities as the separation medium for magnetic liquid separation

Results of an investigation into a new method of magnetic liquid separation, which differs from known ones by the presence of a bilayer separation medium in the form of immiscible ferromagnetic liquids of different densities, are presented. During the separation in a bilayer medium, the equilibrium condition of a particle on a flat surface, which is written according to the Young law and Neumann rule, should be supplemented by the linear tension of a curve-phase interface surface. The linear tension is the force and energy barrier, which prevents fastening of small particles of precious metals at the phase interface, and the cause of their effective separation into a heavy fraction. The method of magnetic liquid separation is tested for concentrates containing platinum group metals. It is established that, during the separation in the bilayer medium, the recovery of platinum group metals into the heavy fraction is 25.89%, while that for the waterbased ferromagnetic liquid is 19.73%. The quality of the heavy fraction makes gives the opportunity to direct it to the hydrometallurgical stage bypassing the copper plant, which increases the recovery of precious metals by 5.0 abs %.

Recovery of Platinum Group Metals from Spent Catalysts Using Electroless Nickel Plating and Magnetic Separation

Recovery of Platinum Group Metals from Spent Catalysts Using Electroless Nickel Plating and Magnetic Separation

Technical note: Flotation as a method for concentration of precious metals in electric arc furnace slag

Automobile exhaust catalysts and electronic equipment, for instance, are rich in platinum group metals (PGMs). At the end of their lifecycles catalytic converters are smelted in electric arc furnaces (EAF) for PGM recovery. With approx. 40ppm, PGM depleted EAF slags still contain significantly higher amounts of PGMs than common primary sources (3–10ppm), in contrast to which the material is oxidic or elementary. Until present, there is no utilisation potential for oxidic EAF slag material. Flotation emerged as a possible option for enriching PGMs from EAF slag. Highest enrichment factor (107±9) was determined for Pt by flotation with sodium O,O′-diethyl dithiophosphate (Na-DEDTP) as collector and polypropylene glycol (PPG) as frother. The Pt content of the concentrate was approx. 1500ppm at a recovery rate up to 17±4%.

A Study on the Utilization of Magnetite for the Recovery of Platinum Group Metals from Chloride Solution

ABSTRACTThe recovery of platinum group metals (PGMs) from chloride solution using magnetite was investigated. The adsorption of platinum, palladium, and rhodium in chloride medium onto synthetic magnetite powders were studied at different pH conditions, contact time, sodium chloride concentrations, and initial Pt, Rh, and Pd concentrations. Platinum and palladium uptake by magnetite was at a maximum at pH 6–7, and pH 3–4 for rhodium after 24 h with 0.1 mol/dm3 sodium chloride at an initial PGM concentration of 0.05 mol/m3. A sorption mechanism for PGMs was discussed based on the results.

A bridge between liquid–liquid extraction and the use of bacterial communities for palladium and platinum recovery as nanosized metal sulphides

The Platinum Group Metals (PGM) are rare in the Earth's crust and in the past years their use had a considerable expansion limiting their availability, which justifies PGM's high commercial value and demand. Therefore, PGM recovery from secondary sources is very important from both economic and environmental points of view.In recent years, several methods for PGM removal have been investigated. Our research group has been studying the removal/recovery of PGM using both chemical (liquid–liquid extraction) and biological methods (using anaerobic bacterial communities).The aim of this study was to combine these two chemical and biological approach technologies, for PGM recovery. For that purpose, Pd(II) and Pt(IV) present in aqueous phases, were extracted to organic phases composed by N,N′-dimethyl-N,N′-dicyclohexylsuccinamide (DMDCHSA) and N,N′-dimethyl-N,N′-dicyclohexyltetradecylmalonamide (DMDCHTDMA) in 1,2-dichloroethane, respectively, with an extraction efficiency of 79% for Pd(II) and 99% for Pt(IV). The metals in the loaded organic phases were then stripped with seawater, a low-cost solution largely available in nature, with efficiencies of 100% for Pd and 86% for Pt. Finally, the metals were precipitated and recovered using metabolic products produced by a community enriched for sulphate-reducing bacteria. The palladium precipitated completely, while 86% of platinum was precipitated. During the precipitation process sulphide concentration in the solution decreased and the analysis of the precipitates was consistent with the formation of nanosized PdS and PtS2.To our knowledge, this research shows, for the first time, the potential of combining liquid–liquid extraction with the use of bacteria aiming platinum and palladium recovery, as metal sulphides, from aqueous media.

Thermal Balance of the Magneto-Hydro-Dynamic Pump for Recovery of Platinum Group Metals from Spent Auto Catalysts

Every new car should be equipped with the catalyst, which limits the amount of harmful chemical compounds such as NOx, CH and CO emitted to the air. Auto catalyst consists of the ceramic or metallic carrier, on which is the layer with Platinum Group Metals playing catalytic role. There are many methods using for recovery those valuable metals from spent auto catalyst, however evry of those methods have some limitations. Proces described in the article is the modified method of metal collector, which used magnetohydrodynamic pump. Rotary electromagnetic field generates in the liquid metal rotary current, which as a consequence washing out the PGM metals from the ceramic carriers. Considering the possibilities of commercialization of the described method, the energy balance was made. From that balance the energetic efficiency of the unit was determined and the analysis of the temperature distribution was shown thermographycally.

Dissolution of Ceramic Monolith of Spent Catalytic Converters by Using Hydrometallurgical Methods / Rozpuszczanie Monolitu Ceramicznego Zużytych Katalizatorów Na Drodze Hydrometalurgicznej

Catalytic converters contain the catalytic substance in their structure, which is a mixture of Platinum Group Metals (PGMs): platinum, palladium and rhodium. The prices of these metals and a growing demand for them in the market, make it necessary to recycle spent catalytic converters and recovery of PGMs. The ceramic monolith of catalytic converters is still a predominant material in its construction among of multitude of catalytic converters which are in circulation. In this work attempts were made to leach additional metals (excluding Pt) from comminuted ceramic monolith. Classic leachant oxidizing media 10M H2SO4, HCl and H3PO4 were used considering the possibility of dissolution of the ceramic monolith.

A biological cyanide production and accumulation system and the recovery of platinum-group metals from spent automotive catalysts by biogenic cyanide

A system for the biological production and accumulation of cyanide was developed, which was used to recover platinum-group metals (PGMs) from spent automotive catalysts. This two-stage process was proposed to overcome drawbacks of biological cyanidation such as low cyanide production, unsuitable pH for bacterial growth and cyanidation, and difficult access of cyanide lixiviant to the surface of target resources. The batch- and continuous-type cyanide production systems achieved maximum cyanide concentrations of 954.8 and 6594.5mg/L, respectively. The leaching of Pt, Pd, and Rh from ground spent automotive catalysts by the biogenic cyanide was compared with leaching by a chemical NaCN solution. A 1000mg/L biogenic cyanide solution leached Pt, Pd, and Rh at efficiencies of 92.1%, 99.5%, and 96.5%, respectively, at 150°C. The chemical NaCN solution leached these PGMs at efficiencies of 100%, 99.9%, and 100%, respectively, under the same condition. These differences might be due to the effect of dissociated anions and oxygen in the biogenic cyanide. Although the leaching efficiencies by the biogenic cyanide were a little less than those by the chemical cyanide, the feasibility of the biological cyanide production and accumulation system for PGMs leaching was demonstrated.

Effects of Sodium Iso-butyl Xanthate Dosage on The Froth Flotation of Bead Milled Middle Group 1-3 PGM Ore Blend

An investigation was carried out to determine the effects of collector concentration on the grade and recovery in the flotation of middle group 1-3 Platinum Group Metal (PGM) ore mixture. The ore mixture pulp at a relative density of 1.29 was subjected to “bead milling” test, particle size distribution analysis and the 55% passing 75 µm was froth floated at 180, 200 and 220 g/t dosages of sodium isobutyl xanthate (SIBX) and 30 and 80 g/t of Senfroth and Sendep 30D frother and depressant, respectively. The results obtained indicated the predominance of the 38 µm PGM values in the ore and confirmed the need for tertiary milling for better liberation of the PGMs. The grade of the PGM concentrate obtained when dosing at 200 g/t of sodium isobutyl xanthate was highest at 94 g/t and gave the lowest recovery of 53%. The 180 g/t SIBX dosage resulted in highest PGM recovery of 70% and lowest grade of 84 g/t, while dosing at 220 g/t SIBX gave average PGM grades of 90 g/t and recoveries of 60%. The results obtained thus showed that that an SIBX dosage of 180 g/t SIBX would be appropriate when higher recoveries are targeted, while 200 g/t dosage will yield higher grades

The recovery of platinum group metals from low-grade concentrates to an iron alloy using silicon carbide as reductant

CITATION: Malan, W., et al. 2015. The recovery of platinum group metals from low-grade concentrates to an iron alloy using silicon carbide as reductant. Journal of the Southern African Institute of Mining and Metallurgy, 115(5): 375-383.

Recovery of platinum-group metals (PGMS) from spent automotive catalysts: Part II: Automotive catalysts: Structures and principle of operation

Recovery of platinum-group metals (PGMS) from spent automotive catalysts: Part II: Automotive catalysts: Structures and principle of operation

Phosphorus-Based Polymers for Selective Capture of Platinum Group Metals

This work addresses the selective recovery of platinum group metals (PGMs) from aqueous streams, a critical issue within the recycling and metal refining industries aiming to lose zero of the value contained. Herein, selective PGM capture was investigated using three metal-capturing polymeric resins from different manufacturers: a special anion exchanger (Dow), an S-containing chelating resin (Lanxess), and a phosphine oxide containing coordinating resin (Magpie Polymers). The relative affinity of these different materials for the PGMs, as well as copper, was compared under various conditions. It was found that the phosphine oxide based material was the most suitable for the selective capture of PGMs from an oxidizing solution containing high concentrations of copper and counterions. Theoretical calculations using density functional theory (DFT) have shown that the most likely binding of PGMs to this material is a bidentate coordination via the phosphine oxide groups.