Enrichment of valuable metals from silver tailings using the alkali roasting-leaching method

Abstract

To solve the tailings accumulation and mineral resource scarcity issues, this study uses silver tailings as a raw material and sodium carbonate roasting followed by water and acid two-step leaching process to investigate the enrichment of copper, cobalt, and lead. Based on the identification of occurrence forms of copper, cobalt, and lead in the silver tailings, the process parameters of the Na2CO3 roasting and acid leaching were optimized. The silver tailings were mixed with sodium carbonate at a mass ratio of 1:1.3 and roasted at 750 °C for 30 min, and the roasted clinker was leached using water at 80 °C for 15 min. The water leaching residue was then leached using H2SO4 acid at a concentration of 3 mol/L, a liquid–solid ratio of 10 mL/g, and at room temperature for 3 min. We finally obtained leaching efficiencies of 97.02 % and 86.45 % for copper and cobalt, respectively; 79.17 % of lead went into the acid leaching residue. The copper and cobalt were significantly enriched in the polymetallic enriched ore powder at 10.76 and 7.12 times the content in the tailings, respectively, reaching industrial grade that could be used as a new type of ore raw material for the extraction of copper and cobalt. Lead was enriched in the acid leaching residue at a content of 7.61 times that of the tailings and was mixed with the tailings to be further roasted and leached to enrich the lead. These results provide a theoretical foundation for the full resource utilization of metallic tailings.