Recovery of platinum from spent automotive catalytic converters by leaching with aluminium-based salts solutions

The increasing global demand for metals has intensified mining activities, raising serious environmental concerns. Platinum group metals (PGM), classified as critical raw materials (CRM) by the European Union, are essential to modern industries, particularly for automotive catalytic converters. Recycling PGM from spent automotive catalytic converters (SACC) represents a sustainable and circular economy strategy, reducing the dependence on primary mining. In this study, a new hydrometallurgical process was developed for PGM recovery from SACC using an aqueous solution of AlCl₃·6H₂O and Al(NO₃)₃·9H₂O which offers a greener alternative to the harsh aqua regia. A real SACC from a diesel vehicle was used, following its characterization and pretreatment. The characterization confirmed that Pt was the only measurable PGM present in its composition. Key leaching operational parameters, including reagents and solid-to-liquid (S/L) ratios, temperature, and contact time, were optimized, with temperature identified as the critical factor for Pt leaching. Under optimal conditions, the single-step leaching process demonstrated high efficiency, achieving 94 % of Pt extraction. The selective separation of Pt was achieved using the Ambersep 900® anion-exchange resin, followed by Pt elution with a thiourea solution. The process was successfully scaled up 60-fold, demonstrating leaching media reusability over five cycles without loss of efficiency and achieving a Pt concentration of 418 mg·L^-1. The resin adsorbed 97 % of Pt, with 96 % recovery during the desorption step, finally obtaining Pt isolated. A preliminary cost analysis highlights the economic viability of this acid-free recovery method.