Automobile Catalysts Research Articles

Iron capture mechanism for harmless recovering platinum group metals from spent automobile catalyst

ABSTRACT Automotive catalysts are the largest consumption source of platinum group metals (PGMs). When it exceeds its useful life, spent automotive catalysts (SACs) are the most important secondary PGMs resource and are classified as hazardous solid waste. Recycling SAC is a promising solution to alleviate the shortage of PGMs resources for projects and reduce environmental pollution. The technology for recovering PGMs by iron-melting collection can obtain Fe-PGMs alloy and harmless glass slag. In this paper, the spontaneous aggregation and growth behaviour of Fe and PGMs in slag at melting temperature were studied, and the settling velocity of Fe-PGMs particles in the slag was calculated to be 6.68 × 10−3 m/s. The effects of melting time, melting temperature and Fe dosage on PGMs recovery were determined, and the optimal conditions were 10 wt% Fe, 1500°C and 40 min. The toxicity test verifies that the slag obtained is a clean slag harmless to the environment. This work explains the mechanism of Fe collection of PGMs and provides a pathway for efficient and harmless recovery of PGMs from SAC.

Iron Chloride Vapor Treatment for Leaching Platinum Group Metals from Spent Catalysts

AbstractAn efficient and environmentally friendly recovery of platinum group metals (PGMs) from secondary sources is necessary to ensure a sustainable supply of PGMs. In this study, contact with FeCl2 vapor in the presence of metallic Fe was investigated as a useful pretreatment for leaching PGMs from spent automobile catalysts. Fe-PGM alloys were efficiently formed when Pt, Pd, and Rh wires and Rh2O3 powder were subjected to FeCl2 vapor treatment at 1050 K (777 °C) for approximately 40 min. Further, the leachability of the PGMs in spent automobile catalyst samples increased after a similar vapor treatment was applied. When the pulverized spent catalyst sample without pretreatment was leached with aqua regia at 333 K (60 °C) for 60 min, 88% of Pt, 91% of Pd, and 37% of Rh were extracted. Meanwhile, after vapor treatment at 1050 K, 98% of Pt, 97% of Pd, and 87% of Rh were extracted under the same leaching conditions. Thus, the pretreatment with FeCl2 vapor, followed by leaching, is a feasible and effective technique for recovering PGMs from spent catalysts. Graphical Abstract

Separation and Recovery of Palladium (II) and Platinum (IV) from Automotive Catalysts by Solvent Extraction Using Tri-n-butyl Phosphate and Aliquat 336

Pt, Pd, Fe, Ni, and Cr are among the metals found in spent automotive catalysts, which are both environmentally critical and economically beneficial. In this study, solvent extraction methods were utilized to separate and recover palladium (Pd) and platinum (Pt) from wasted car catalyst. The synthetic leach liquor employed in this investigation contains (mg/L): Pd-140, Pt-500, Ni-800, Fe-2000 and Cr-150. The variation of tri-n-butyl phosphate (TBP) in Shellsol D70 from 0.1 to 2 M revealed selective and quantitative Pd extraction even at the lowest extractant concentration. Stripping Pd from loaded organic (LO) phase using 1 M thiourea and 1 M HCl yielded stripping efficiency of 99%. The use of Aliquat 336 at concentrations ranging from 0.05 to 0.5M in the extraction of Pt from Pd free raffinate demonstrated selective extraction of Pt, reaching 99.7% at 0.2M. The use of a McCabe-Thiele plot in 0.2M Aliquat 336 is expected to result in the extraction of more than 99% of Pt in two stages when an A/O phase ratio of 3 is used. The stripping efficiency of Pt from loaded organic (LO) at O/A ratio 6 with 0.5 M thiourea (tu) and HCl was 99.9 percent.

Mechanism of PGMs capture from spent automobile catalyst by copper from waste printed circuit boards with simultaneous pollutants transformation

The traditional pyrometallurgical recycling of nano-sized platinum group metals (PGMs) from spent automotive catalysts (SACs) is an energy-intensive process that requires the addition of large quantities of copper capture and slag-forming reagents. Similarly, pyro-recycling of valuable metals from waste printed circuit boards (WPCBs) is also an energy- and reagent-intensive process that and carries a risk of pollution emissions. Based on the complementarity of composition and similarity of recycling process, synergistic pyro-recycling of SACs and WPCBs allow copper in WPCBs to capture PGMs in SACs and oxides from two waste form slag jointly, which offers benefits of enhanced metal recovery, reduced reagent and energy consumption, and suppressed pollutant emissions. However, the mechanisms of PGMs capture and pollutant transformation in co-smelting remain unknown. Here, we investigated the sub-processes mechanisms of slag formation, brominates fixation, multi-metal distribution and kinetic settlement. Oxides in both wastes support SiO2-Al2O3-CaO slag formation with low melting point and viscosity, where CaO suppresses the emission of brominated pollutants. Copper (50–100 μm) from WPCBs facilitates nano-sized PGMs in SACs recovery through capture and settlement. The results of demonstration experiments indicated a recovery rate of 94.6 %, 96.8 %, 97.2 %, and 98.1 % for Cu, Pt, Pd, and Rh, respectively, with a debromination efficiency exceeding 98 %. The theoretical analysis provides support for the establishment of a synergistic pyro-recycling process for SACs and WPCBs and provides insights into the potential for a greener and more efficient co-recycling of multi urban mines.

Fast and simple method for simultaneous determination of palladium and rhodium in spent automotive catalysts by high-resolution continuum source electrothermal atomic absorption spectroscopy

This work established a novel and fast method for the simultaneous determination of palladium and rhodium in spent automotive catalysts by high-resolution continuum source electrothermal atomic absorption spectroscopy (HR-CS ETAAS). For this purpose, a simple approach for the extraction of Pd and Rh from auto catalysts with aqua regia (HCl + HNO3 (3:1)) leaching was developed. The optimum conditions for leaching of both elements in an open system are 4 h, at 108 °C and a solid-to-liquid ratio of 1:40. Palladium and rhodium concentrations in obtained leachate were determined simultaneously in one firing using the less sensitive adjacent secondary lines for Pd at 360.955 nm (7.7% relative sensitivity) and for Rh at 361.251 nm (2.2% relative sensitivity). The pyrolysis and atomization temperatures were 1200 °C and 2600 °C, respectively. Under these conditions, the limits of detection for Pd (0.19 mg kg−1) and Rh (0.48 mg kg−1) were relatively high but the sensitivity of the developed method corresponds to common concentrations of the elements in spent automotive catalysts. The repeatability of the method expressed as a relative standard deviation was typically 10% for Pd and 7% for Rh.The trueness of the method was confirmed by analysis of the certified reference material – spent automobile catalyst (ERM EB 504). The recoveries of Pd and Rh from the spent automobile catalyst were 96.9%, and 87.9%, respectively. The method was successfully applied to the simultaneous determination of Pd and Rh in spent automotive catalysts without preliminary chemical separation.

Alzheimer and Parkinson diseases, frontotemporal lobar degeneration and amyotrophic lateral sclerosis overlapping neuropathology start in the first two decades of life in pollution exposed urbanites and brain ultrafine particulate matter and industrial nanoparticles, including Fe, Ti, Al, V, Ni, Hg, Co, Cu, Zn, Ag, Pt, Ce, La, Pr and W are key players. Metropolitan Mexico City health crisis is in

The neuropathological hallmarks of Alzheimer's disease (AD), Parkinson's disease (PD), frontotemporal lobar degeneration (FTLD), and amyotrophic lateral sclerosis (ALS) are present in urban children exposed to fine particulate matter (PM2.5), combustion and friction ultrafine PM (UFPM), and industrial nanoparticles (NPs). Metropolitan Mexico City (MMC) forensic autopsies strongly suggest that anthropogenic UFPM and industrial NPs reach the brain through the nasal/olfactory, lung, gastrointestinal tract, skin, and placental barriers. Diesel-heavy unregulated vehicles are a key UFPM source for 21.8 million MMC residents. We found that hyperphosphorylated tau, beta amyloid1-42, α-synuclein, and TAR DNA-binding protein-43 were associated with NPs in 186 forensic autopsies (mean age 27.45 ± 11.89 years). The neurovascular unit is an early NPs anatomical target, and the first two decades of life are critical: 100% of 57 children aged 14.8 ± 5.2 years had AD pathology; 25 (43.9%) AD+TDP-43; 11 (19.3%) AD + PD + TDP-43; and 2 (3.56%) AD +PD. Fe, Ti, Hg, Ni, Co, Cu, Zn, Cd, Al, Mg, Ag, Ce, La, Pr, W, Ca, Cl, K, Si, S, Na, and C NPs are seen in frontal and temporal lobes, olfactory bulb, caudate, substantia nigra, locus coeruleus, medulla, cerebellum, and/or motor cortical and spinal regions. Endothelial, neuronal, and glial damages are extensive, with NPs in mitochondria, rough endoplasmic reticulum, the Golgi apparatus, and lysosomes. Autophagy, cell and nuclear membrane damage, disruption of nuclear pores and heterochromatin, and cell death are present. Metals associated with abrasion and deterioration of automobile catalysts and electronic waste and rare earth elements, i.e., lanthanum, cerium, and praseodymium, are entering young brains. Exposure to environmental UFPM and industrial NPs in the first two decades of life are prime candidates for initiating the early stages of fatal neurodegenerative diseases. MMC children and young adults-surrogates for children in polluted areas around the world-exhibit early AD, PD, FTLD, and ALS neuropathological hallmarks forecasting serious health, social, economic, academic, and judicial societal detrimental impact. Neurodegeneration prevention should be a public health priority as the problem of human exposure to particle pollution is solvable. We are knowledgeable of the main emission sources and the technological options to control them. What are we waiting for?

Study on process and mechanism of cordierite recovery by flotation from spent automobile catalysts

Flotation, as one of the most likely methods to improve the recovery efficiency of cordierite from spent automotive catalysts, requires systematic research and optimization. In this study, an efficient flotation process with cordierite recovery of 85.2 % was proposed. The mechanism of flotation was studied by SEM-EDS, XPS, AFM. SEM-EDS confirmed that Si distributed mainly in the cordierite carrier of spent automotive catalysts and Al (not in cordierite structure) distributed mainly in the washcoat. XPS results showed that the adsorption strength of NaOL (sodium oleate) was greater than that of Na2O⋅3SiO2 (sodium silicate) on the surface of washcoat. AFM results showed that the adsorption effect of Na2O⋅3SiO2 was stronger than that of NaOL on the surface of cordierite carrier. In summary, internal reasons to realize cordierite recovery from spent automobile catalysts by flotation were the selective adsorption of NaOL on the surface of washcoat and Na2O⋅3SiO2 on the surface of cordierite.

Emergence of Bio-hydrometallurgy to Achieve Sustainable Process Development Goals in Extractive Metallurgy

The stringent environmental regulations and growing awareness of the low-carbon economy are presenting immense challenges to metallurgical operations, one of the major sectors with high emissions. Hydrometallurgy has been identified as a lower-emission technology in comparison to the high-temperature smelting and melt-refining processes. The close monitoring of traditional hydrometallurgical operations, however, does not fulfil the criteria for a sustainable, low-emission process. Recently, biotechnology has emerged as a green alternative within the hydrometallurgical domain, albeit significantly different from the basics involved in the process. Although the application of microbial activity has been successfully established in chalcopyrite leaching and bio-oxidation of gold-bearing minerals, the acceptability of bio-hydrometallurgy for other minerals and materials is still limited due to a wide research gap to connect solution chemistry, microbial activity, and extractive metallurgy. In general, a large portion of the total chemical consumption occurs in pre-treatment and/or leaching operations; hence, the primary application of microorganisms at the forefront can significantly minimize the overall consumption. Demonstrated applications in waste printed circuit boards and spent automobile catalysts have curtailed excessive acid usage, while the energy-intensive baking/roasting of monazite is successfully altered by microbial processing. Furthermore, the remarkable reduction in carbon footprints by the green biotechnology application in hydrometallurgy has been evaluated, which indicates sustainability in process metallurgy.

A Selective Separation of Platinum Group Metals from the Fe-PGM Alloy Using Electrodeposition Combined with Electrochemical Dealloying

In the European automotive industry, a considerable volume of recalled car catalysts stems from diesel vehicles, characterized by their high silicon carbide (SiC) content. Processing such materials poses notable challenges compared to gasoline vehicle catalysts. The presence of SiC demands additional time and energy in electric arc furnace processing, with SiC’s high melting point and strong reducing properties complicating separation. The Fe-PGM alloy obtained after pyrometallurgical treatment of these SiC-rich catalysts presents hurdles for hydrometallurgical processing. With high silicon content, the alloy resists corrosion in sulfuric acid, impeding solubility and hindering progress in the recovery process. This article explores an innovative approach for selectively extracting platinum group metals (Pt, Pd, Rh) from Si-rich Fe-PGM alloys. Traditional hydrometallurgical methods struggle due to the alloy’s near-immunity to acid leaching. The study presents chemical leaching results and proposes electrodeposition combined with electrochemical dealloying as a feasible solution. This method, aiming for selective metal separation, seeks to enhance recovery process profitability by producing pure metals.

Tailored synthesized Pt/ZSM-5 catalysts with excellent water vapor stability for low temperature oxidation of CO and C3H6

Pt supported on ZSM-5 catalysts are important for the catalytic oxidation of CO and volatile organic compounds (VOCs) due to their extraordinary performance at low temperatures and economic purposes. However, achieving complete oxidation at low temperatures and stability under water vapor remains challenging. Herein, we report the synthesis of several loading of Pt on a ZSM-5 catalyst via a flame synthesis technique. The Pt/ZSM-5 exhibited good activity towards complete CO and C3H6 oxidation at low temperatures due to the interaction between the Pt and ZSM-5. The combined effect of the PtOx (Pt2++Pt4+) and lattice oxygen from Pt (OPtOx) as the active centers in Pt/ZSM-5 favors the complete oxidation with high reaction rates, TOFs, and low activation energies (Ea), which is well consistent with the increasing concentration of the (Pt2++Pt4+)/Pt0. Pt/ZSM-5 presents a long-time tolerance to water vapor deactivation even at temperatures below 80 °C. The distributed Pt favor the reaction occurring through the Langmuir-Hinshelwood (L-H) route. The excellent catalytic results indicate an attractive approach for designing supported Pt on ZSM-5 catalysts for automobiles and industry exhausts.

Trends of Technological Development of Platinum Group Metal Recycling: Solubilization and Physical Concentration Processes

Spent automobile catalysts are the most important secondary resource for platinum group metals (PGMs), and their recycling is essential not only to ensure a steady supply of PGMs but also to preserve the natural environment. However, several factors limit the efficiency of PGM recovery in current recycling processes. Specifically, PGMs represent a small proportion of the entire catalyst and are difficult to dissolve in aqueous solutions for subsequent separation. In recent decades, multiple technologies have been developed to make the recycling of PGMs more efficient and environmentally-friendly. Herein, we introduce the typical industrial processes for recovering PGMs from spent catalysts, along with established and emerging trends in the technological development of PGM recycling. Furthermore, we review novel recycling techniques for converting PGMs in spent catalysts into more soluble states and/or physically concentrating PGMs from spent catalysts.

Preferential recovery and separation of rhodium in the concentrated hydrochloric acid using thin-layer oil membrane extraction based on laminar flow

The unique characteristics of the interface environment that distinguish bulk phases can promote or inhibit certain reactions and significantly change chemical reactivity. In this work, the separation of Rh (III) and Fe (III) on the surface of concentrated hydrochloric acid was studied by a thin-layer oil membrane (TOM) extraction based on laminar flow with 18-Crown-6-ether (18C6) as the extractant. A new phenomenon different from conventional extraction was found. The TOM extraction prefers to identify hydrated Rh (III) anions rather than H3O+ ions at the interface due to a lower concentration of free hydrated hydrogen ions on the surface of concentrated hydrochloric acid. However, during the conventional extraction, the H3O+ ions in the bulk phase are preferentially extracted by the 18C6, and then the hydrated rhodium (III) anions could be extracted by the protonated crown ether through the ion association mechanism. Besides, it was found that the TOM extraction could enhance extraction of hydrated rhodium (III) anions by taking advantage of the uniqueness of rhodium species on the interface, and by adjusting the thickness of the oil membrane and the flow rate of the aqueous phase. The decrease in the oil membrane thickness and the increase in the flow rate of the aqueous phase are conducive to the complexation of 18C6 with the hydrated rhodium (III) at the interface, which can better reflect the targeting and the controllability of extracting single species of hydrated rhodium (III) ions at the interface. Considering the applications of selective recovery of Rh (III) from concentrated hydrochloric acid leaching solution of waste automobile catalyst, the selective separability of Rh (III) to other coexisting metal impurity ions such as Fe (III), Cu (II), Co (III) and Ni (II), was also evaluated. This work provides a new strategy for preferential recovery and separation of rhodium in concentrated hydrochloric acid leach solutions containing other base metal ions for possible future's application.

Separation of Palladium, Platinum and Rhodium from Metallic Mixture by Selective Dissolution with Hydrochloric Acid Solutions Containing Oxidizing Agents

ABSTRACT Platinum group metals are widely used in the manufacture of advanced materials due to their excellent physical and chemical properties. Especially, palladium (Pd), platinum(Pt), and rhodium(Rh) are used as catalysts for automobiles. In general, combination of pyrometallurgical and hydrometallurgical process is necessary to recover PGMs. In this work, the separation of Pd, Pt, and Rh from the metallic mixture was investigated by selective dissolution using HCl solutions containing oxidizing agents such as H2O2 and NaClO3. As a diluent for the leaching medium, either water or ethylene glycol (EG) was employed and the dissolution behavior of the three metals was compared. Selective dissolution of 99.9% Pd from the metallic mixture was achieved by using 1 M HCl and 1.225 M M H2O2 (H2O medium, 40°C, 30 min), while that of 99.9% Pt was possible by using 5 M HCl and 0.5 M NaClO3 (H2O medium, 60°C,120 min). By these two-step dissolution, Rh metal remained in the residue. A simple process was proposed to separate Pd, Pt, and Rh from their metallic mixture by selective dissolution.

Separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts with monothio-Cyanex 272 and trioctylamine

Separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts with monothio-Cyanex 272 and trioctylamine

Recycling of platinum group metals from exhausted petroleum and automobile catalysts using bioleaching approach: a critical review on potential, challenges, and outlook

Recycling of platinum group metals from exhausted petroleum and automobile catalysts using bioleaching approach: a critical review on potential, challenges, and outlook

The Importance of Recovery of PGMS from Catalysts – A Case Study of Recycling Network in Poland

Abstract Combustion engines are the main driving force of passenger cars, trucks or buses. Engines burn fuels, and as a side effect, release many pollutions to the atmosphere. Car manufacturers had been aware of a need of lowering the amount of exhaust fumes. This brought on the market the first catalytic converters. Nowadays automobile catalyst manufacturing is the largest sector of demand of PGMs (mainly platinum, palladium and rhodium), and unfortunately consumption and future demand of there critical metals is getting higher. Over the past two decades, most countries around the world have developed and implement solutions that would minimize the impact of the growing number of cars on the environment. One solution contributing to this is the organisation of an end-of-life car collection and recycling network, which is now an integral part of automotive industry. The main drivers for the development of such network were stricter environmental regulations and economic conditions. The development of recycling is also becoming more popular in Poland. However, catalyst recycling system is still not transparent to all stakeholders. Due to the huge variety of catalysts and their different structure and composition of elements from the PGMs group, the valuation of their price before they are recycled is not obvious. This raises a lot of controversy and does not inspire trust among those who recycle their catalysts. The aim of this work is to show how the management of used catalytic converters looks like in Poland and how developed is network of catalysts recycling in Poland. At the same time this will show how important it is in terms of a circular economy and the recovery of valuable raw materials from a group of PGMs.

Sampling in a precious metals refining plant—A practical approach for a complex problem

Umicore Precious Metals Refining is one of the world’s largest precious metals recycling facilities. This plant recycles very diverse waste streams containing precious and other non-ferrous metals. More than 200 different types of raw materials are being processed here, varying from complex mining concentrates and refining residues coming from the mining industry and other smelters up to precious metals containing production scraps and end-of life materials such as electronic scrap and car catalysts. All these materials need to be sampled and analysed, of course, to determine the metal content (and so the value) of each individual lot. It is clear that heterogeneity rules in this process! Next to the obvious heterogeneity of the material itself, there is also a huge variety e.g. in lot size, in packaging, in physical appearance of the different materials, … which is also to be taken into account during the sampling process. To take all these hurdles, the necessary resources are … unfortunately… – not unlimited. In this article we will gain more insight on how this complex problem is tackled in practice within Umicore, with respect for the Theory of Sampling. A couple of major specific sampling lines have been developed and designed in particular to be able to deal with the variety in physical appearance of the materials itself. Additionally, a large number of sampling procedures are made up in a modular way, to be able to cope with the necessary flexibility demanded for. Some examples will be illustrated and described more in detail, with specific attention to the most important influencing circumstances. Furthermore, the way the overall performance and quality of this whole process is supervised, will be explained. And finally, we’ll discuss some special cases where“nothing seems to be what expected for”…

Modelling of the Flow in the Process of Washing Out Automotive Catalyst Carriers with the PbLi Alloy.

The process of platinum recovery from used car catalysts is highly desirable for both economic and environmental reasons. From the many available methods of processing used car catalysts, the article conducted both numerical and experimental studies using a device based on the collector metal method with lead as a modified medium through a magnetohydrodynamic pump for washing platinum from the channels of the ceramic catalyst carrier. It was assumed that lead alloys with the addition of lithium increase the extraction of platinum from thin catalytic layers and accelerate the platinum dissolution reaction in the Pb-Li alloy, which is the result of a greater affinity of lithium for platinum compared to lead. This assumption was verified by numerical simulations as well as laboratory tests. Tests were carried out for the secondary supply voltage range between 40 and 60 V and the catalyst flushing time between 240 and 480 s. Graphical results of the research were discussed.

A Review of Recovery of Palladium from the Spent Automobile Catalysts

The spent automobile catalysts (SAC) is the major secondary source of palladium and the production of SAC is increasing rapidly over years. The price of palladium keeps rising over the years, which demonstrates its preciousness and urgent industrial demand. Recovering palladium from the spent automobile catalysts benefits a lot from economic and environmental protection aspects. This review aims to provide some new considerations of recovering palladium from the spent automotive catalysts by summarizing and discussing both hydrometallurgical and pyrometallurgical methods. The processes of pretreatment, leaching/extraction, and separation/recovery of palladium from the spent catalysts are introduced, and related reaction mechanisms and process flows are given, especially detailed for hydrometallurgical methods. Hydrometallurgical methods such as chloride leaching with oxidants possess a high selectivity of palladium and low consumption of energy, and are cost-effective and flexible for different volume feeds compared with pyrometallurgical methods. The recovery ratios of palladium and other platinum-group metals should be the focus of competition since their prices have been rapidly increased over the years, and hence more efficient extractants with high selectivity of palladium even in the complexed leachate should be proposed in the future.

A Combined Deep Eutectic Solvent-Ionic Liquid Process for the Extraction and Separation of Platinum Group Metals (Pt, Pd, Rh).

Recovery of platinum group metals from spent materials is becoming increasingly relevant due to the high value of these metals and their progressive depletion. In recent years, there is an increased interest in developing alternative and more environmentally benign processes for the recovery of platinum group metals, in line with the increased focus on a sustainable future. To this end, ionic liquids are increasingly investigated as promising candidates that can replace state-of-the-art approaches. Specifically, phosphonium-based ionic liquids have been extensively investigated for the extraction and separation of platinum group metals. In this paper, we present the extraction capacity of several phosphonium-based ionic liquids for platinum group metals from model deep eutectic solvent-based acidic solutions. The most promising candidates, P66614Cl and P66614B2EHP, which exhibited the ability to extract Pt, Pd, and Rh quantitively from a mixed model solution, were additionally evaluated for their capacity to recover these metals from a spent car catalyst previously leached into a choline-based deep eutectic solvent. Specifically, P66614Cl afforded extraction of the three target precious metals from the leachate, while their partial separation from the interfering Al was also achieved since a significant amount (approx. 80%) remained in the leachate.