Selective Recovery of Platinum Group Metals from Spent Automotive Catalysts by Leaching and Solvent Extraction

Abstract

Platinum group metals (PGMs) play an important role in the automotive industry as key components of exhaust catalysts. Recycling of PGMs from secondary resources, such as waste products, is encouraged to ensure their sustainability. A highly e cient and environmentally benign technique for the separation of PGMs is currently required. In the present study, the recovery of PGMs from a spent automotive catalyst was investigated using the trioctyldodecyl phosphonium chloride (P 8,8,8,12 Cl) ionic liquid (IL) as the PGM extraction solvent. First, leaching from the catalyst was investigated. Pt and Pd are selectively extracted into undiluted P 8,8,8,12 Cl from the 5 mol L 1 HCl leachate containing various metals together with Pt, Pd, and Rh. Subsequently, Rh is extracted into fresh P 8,8,8,12 Cl from the ra nate adjusted to an appropriate HCl concentration. Mutual separation of Pt and Pd is possible by stripping processes. Some common metals coextracted with PGMs, such as Fe, Cu, and Zn, are removed by each stripping process. Recovery of high purity Pt, Pd, and Rh is achieved by the proposed recycling process. The results demonstrate that separation using phosphonium-based ILs is useful for recycling PGMs.

Promising polymer-assisted extraction of palladium from supported catalysts in supercritical carbon dioxide

“…The extraction methods such as pyrometallurgical processes and various hydrometallurgical and leaching methods [49] have been reviewed for the recovery of precious metals from supported catalysts [50,51]. Among them, alternative methods such as supercritical fluids extraction (scCO2 and supercritical water), ionic liquid-assisted extraction [52], ultrasound-assisted pre-treatments for bioleaching [53] and microwave-assisted leaching [44] are considered to also have good potential to leach precious metals such as Pd. Nevertheless, there are still some challenges to achieving environment-friendly and sustainable recycling for precious metals with a high recovery rate.…”

Liquid‐ and Solid‐based Separations Employing Ionic Liquids for the Recovery of Platinum Group Metals Typically Encountered in Catalytic Converters: A Review

“…Overall, 94 % Pt, 90 % Pd, and 64 % Rh in the acidic leachate are accessed. [180] An IL-based microemulsion process for extraction of Au III , Pd II , and Pt IV from their model mixed solution and their subsequent recovery in highly pure metallic form (> 99 %) has been developed by Ngyen et al [181] The [P 66614 ]Cl/triton X-100 (TX-100)/H 2 O microemulsion (IL-in-water microemulsion) is an environmentally benign system that encompasses all the positive aspects that ILs have to offer, while at the same time its low viscosity, high selectivity and recyclability without loss of performance render it an ideal candidate for industrial applications. Prior to extraction experiments, the phase behavior and the structure of the microemulsion was fully determined.…”

“…Mixing of the Rh containing raffinate acidified to 2.0 m HCl with fresh IL leads to 80 % extraction of Rh, 80 % of which can be subsequently recovered by Na 2 SO 3 leading to a 99 % pure Rh solution. Overall, 94 % Pt, 90 % Pd, and 64 % Rh in the acidic leachate are accessed [180] …”

Recovery of Noble Metals from Spent Catalysts: A Review

“…Although using KHSO4 salt resulted in a slightly higher leachability rate of Pt, using NaHSO4 was considered economically friendly. In [37,38], novel Phosphonium (P8,8,8,12Cl)-based ionic liquid was used to separate the PGMs from the automobile leach liquor. Initially, 570 g of the spent catalyst was mechanically crushed followed by ball milling for 30 to 300 mins until the particle size of 75 µm is attained.…”