Microscopic mechanism of impurity effects on gold capturing by bismuth in decoppered anode slime obtained from copper smelting

Bismuth (Bi) within copper anode slime is a promising metal for gold (Au) capture, though its efficacy is impacted by common impurities whose microscopic mechanisms are not well understood. This study employs density functional theory (DFT) to systematically investigate the adsorption of an Au atom on the pristine Bi(001) surface and on surfaces doped with common impurities (Na, Pb, Si, Sb, and As). On the stable pristine Bi(001) surface, Au preferentially adsorbs at the hollow site with an energy of −2.36 eV, forming an Au-Bi metallic bond. Doping with Si, Sb, or As is found to significantly enhance Au adsorption. The Si-doped system is proved to be the most effective, yielding a superior adsorption energy of −3.21 eV. Electronic structure analysis attributes this enhancement to the formation of strong covalent bonds between the Au atom and the dopant, coupled with substantial charge transfer. Specifically, the Au-Si bond exhibits the strongest interaction, with charge transfer from Si to Au (0.596 e) being significantly higher than in Sb- and As-doped systems. These findings identify Si as an effective promoter for gold capture, providing a theoretical foundation for optimizing recovery processes by strategically leveraging specific elemental impurities.