Cyanide-free leaching of gold from used Au/MO_x catalysts assist by oxidative carbonylation

Recycling gold from used catalysts is significant for economic and environmental sustainability. Conventional methods, which heavily rely on the cyanide process, have posed significant environmental, health, and safety challenges. Herein, this study presents a novel approach for gold leaching from spent Au/metal oxide (Au/MOx) catalysts coupled with an oxidative carbonylation reaction. This tandem process not only efficiently dissolves Au nanoparticles from used heterogeneous Au catalysts into soluble AuI2- complex without using toxic cyanide, strong acids or oxidants, but also produces useful nitrogen-containing carbonyl compounds. Mechanistically, the leaching process is initiated by the in-situ generation of hydroiodic acid during the oxidative carbonylation reaction. This new approach has potential guide to the metal recovery and the design of stable heterogeneous catalysts.