Efficient recycling of Au(S2O3)23− from alkaline leach solutions using diphenylamine-rich Cu-MOF via local exotherms of DMF

Recycling gold from electronic waste is essential for environmental protection and resource sustainability. However, the design of adsorbents for effective recycling of Au(S2O3)23− from alkaline leach solutions is of great challenge and has not been investigated by using MOFs. Herein, we report the design and preparation of a Cu-MOF based on the structural characteristics of Au(S2O3)23−, which is constructed by 4,4′-di carboxy diphenylamine and Cu2-paddlewheel. Cu-ADA-53 demonstrates ultra-high adsorption capacity of 206.19 mg g-1, and the gold recovery in actual alkaline leach solutions is more than 99 %. X-ray photoelectron spectroscopy, thermodynamic study, and density functional theory calculations reveal the excellent performance of Cu-ADA-53 for Au(S2O3)23− results from the abundant Lewis base diphenylamine groups and open copper sites. More importantly, different from pore diffusion-promoting adsorption, the axial coordination DMF of Cu2-paddlewheel fell off into the water phase and then released heat locally at the adsorption sites. The local exotherms increase the temperature of the adsorption sites, further promoting the adsorption of Au(S2O3)23− by Cu-ADA-53. The local exotherms at adsorption sites provide a novel insight to efficiently recover Au(S2O3)23−.