Prioritized extraction of gold and silver from lead anode slime by Cu(I)/Cu(II)-based catalytic wet air oxidation leaching method

Abstract

Lead anode slime (LAS) is an important industrial by-product containing gold and silver. The traditional treatment method has the problems of long gold and silver recovery process, low direct recycle rate, serious capital backlog, and difficult management of fumes. In this paper, a new strategy for extracting Au and Ag prior from LAS was proposed. The Cu(I)/Cu(II)-based catalytic wet air oxidation (CWAO) technology was used to leach Ag and base metals from LAS to enrich Au first. Then, Ag was selectively precipitated from the leaching solution by introducing NaI. Consequently, the whole extraction process consumed only 1.5 h, and the total recovery rate of Au and Ag were both 99.6 %. The enrichment factor of Au reached 30.2 and the occurrence form in leaching residue may be Au(Te, Se) intermetallic compound. The investigations on catalytic behavior and oxidation mechanism indicate reaction time has a power function with Cu amount. The main path of Cu(I)/Cu(II) redox cycle is the direct oxidation by O₂, while the oxidation by reactive oxygen species is the secondary path. Finally, the material flow of Ag, Au, Te, and Se was analyzed. The proposed process provides a reference for extracting of Au and Ag from similar materials.