Comprehensive Recovery of Valuable Metals from Lead-Silver Residue Using Low-Temperature Alkaline Smelting

This study provides an effective solution to the recovery issue of hot acid leaching residue (lead-silver residue) from the hydrometallurgical process of Zn, in the form of low-temperature alkaline smelting. Investigations were carried out to study lead-silver residue as the raw material, sodium carbonate and salt as flux, carbon powder as the reductive agent, and the effects of salt usages, melting temperature, melting time, carbon powder usages, and sodium carbonate usage. The influence of relative factors was also verified. Under the optimum conditions, that is, using salt and sodium carbonate mass ratio as 4/6, melting time 60 min, temperature 900 ℃, carbon powder usage 0.15 times the raw materials, and sodium carbonate usage 1.215 times the raw materials, the average direct recovery of lead and silver reached up to 85.1% and 87.5%, and the average residual rate of lead and silver in the molten residue were 11.0% and 7.8%, respectively. The mechanism of immobilizing sulfur was also studied. The analysis of the XRD pattern showed that iron exists as Fe 3 O 4 , sulfur and zinc exist as ZnS, and lead and silver exist as crude lead. This method has one-step lead and silver recovery and sulfur immobilization.