Selective separation of base metals and high-efficiency enrichment of precious metals from scrap copper anode slime

Abstract

In this study, a clean and effective integrated process for selectively separating base metals and high-efficiency enriching precious metals from scrap copper anode slime was investigated. O2-enriched roasting combined with H2SO4-NaCl leaching was used in the decopperized process to avoid the scattered distributions of As & Sn and enhance the selective leaching efficiencies of Cu, Ni, and As. The obtained leachate containing Cu, Ni, and As can be sent to the existing electrolyte purification process. Then, alkaline xylitol leaching was applied to selectively separate Pb greatly avoiding its negative impact on the subsequent process, and Pb-containing leaching solution was used to prepare lead electrodeposition electrolyte. Sn was recovered in the form of sodium stannate by soda roasting-alkaline leaching. Results of scale-up experiment showed that the direct leaching efficiencies of Cu, Ni, As, Pb, and Sn under the optimum conditions were 99.3 %, 96.9 %, 98.6 %, 98.1 %, and 98.9 %, respectively. Ag and Au were maximally remained in the residue. Furthermore, three leaching solutions generated in the proposed process can be treated in an environmentally friendly way. Therefore, it was a high-efficiency and eco-friendly method for SCAS to realize the comprehensive utilization of the base metals and reduced risks of secondary pollution.