Sustainable hydrothermal leaching for platinum recovery from petrochemical spent catalysts: experimental study and process optimization

This study investigates hydrothermal leaching as a sustainable strategy for platinum recovery from alumina-based spent petrochemical catalysts, enabling operation under relatively moderate conditions with reduced acid consumption. Following catalyst pretreatment by fine grinding (< 0.1 mm) and decoking at 550 °C for 10 h, platinum was leached using various solvents, among which hydrochloric acid showed the highest efficiency. Leaching performance was quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES), and the effects of time, temperature, HCl concentration, and pulp density were optimized using Response Surface Methodology. Under optimized conditions (7.29 h, 165 °C, 2.67 M HCl, and 75 g L−1 pulp density), a platinum recovery of 92.24% was achieved, representing approximately a sixfold increase compared with conventional ambient-temperature leaching. These results demonstrate that hydrothermal processing can significantly enhance dissolution kinetics while offering improved process efficiency and environmental compatibility relative to conventional methods.