An electrometallurgical and mechanochemical approach for the recovery of platinum group metals from spent automotive catalysts

In response to the escalating scarcity of resources, the practice of recycling waste has emerged as a pivotal strategy for sustainable development. In the present study, an innovative method is introduced to enhance the recovery of platinum group metals (PGMs) from spent automotive catalysts (SACs), involving an integrated electrochemical metallurgy process integrating mechanochemical reduction pretreatment and electrochemical leaching. An in-depth exploration on the influences of mechanochemical ball-milling parameters and electrochemical leaching conditions on PGM recovery yielded insightful results. Notably, Zn emerges as a key catalyst to promote the generation of highly reactive PGM particles, facilitate grinding, reduce platinum group metal oxides, and alloy with PGMs. The mechanochemical reduction pretreatment significantly reduces the apparent dissolution activation energies of Pd, Pt, and Rh from 40.1 kJ/mol, 43.7 kJ/mol, and 62.5 kJ/mol to 13.2 kJ/mol, 17.5 kJ/mol, and 22.1 kJ/mol, respectively. Following optimization through orthogonal experiments, the leaching efficiencies of Pd, Pt, and Rh reached exceptional levels: 98.5 %, 98.1 %, and 93.3 %, respectively. This study unveils a highly efficient and practical approach for leaching PGMs from SACs, which is conducive to sustainable resource management.