A review of recent studies into hydrometallurgical methods for recovering PGMs from used catalytic converters

Demand for the 3 PGMs - platinum, palladium and rhodium has been steadily increasing, largely as a result of the growing use of the metals in autocatalytic converters. Due to the challenges in the PGM mining industry, studies to recover PGMs from autocatalytic converters have been increasing. In this regard, hydrometallurgical and pyrometallurgical processes have dominated the research field, with pyrometallurgical processes enjoying widespread adoption in the autocatalytic converter recycling industry. However, pyrometallurgical based processes are expensive, require specialized equipment, are highly energy consuming and produce toxic combustion products. Hydrometallurgical processes do not suffer from some of these problems and in that regard, may be favourable for recycling auto converters. Furthermore, the use of less toxic, less flammable extractants like ionic liquids for recovering the PGMs out of solution presents benefits in terms of increased recoveries and safety of operating conditions. Studies for the recycling of PGMs by leaching and extraction have therefore been increasing, and the use of novel extractants like ionic liquids has also been investigated in the literature.