Synergistic leaching of palladium and silver from spent acetylene hydrogenation catalyst via hydroxyl/cyanide radicals from H₂O₂/acetonitrile with maximized alumina support retention

Recycling precious metal active components and supports from spent catalysts is critical for resource utilization and environmental sustainability. Herein, we developed a hydroxyl/cyanide radicals oxidation strategy to achieve efficient recovery of Pd and Ag from spent acetylene hydrogenation catalysts while maximizing alumina support retention. Key parameters influencing Pd/Ag leaching efficiencies and support preservation were systematically investigated, and the underlying leaching mechanisms of the precious metals were elucidated. Under the synergistic action of multiple reactive species (•OH, •CN, O₂• − , and 1 O₂) from H₂O₂ and acetonitrile, Pd and Ag leaching efficiencies reached 100.00 % and 90.91 %, respectively. Kinetic analysis revealed that Pd and Ag leaching was dominated by chemical reaction control. Characterization of the recycled alumina (R-Al 2 O 3 ) confirmed that its crystal structure, surface acid-base properties, and elemental composition were largely preserved. Notably, R-Al 2 O 3 exhibited 96 % retention of crushing strength, 83.79 % retention of average pore size, and 88.24 % retention of total pore volume. This strategy not only enables effective precious metal recovery but also maintains the structural integrity of the carrier, providing a sustainable route for the industrial reuse of spent catalysts.