Leaching of zinc sulfide in alkaline solution via chemical conversion with lead carbonate

A novel hydrometallurgical process for recovering Zn from ZnS in alkaline solution via chemical conversion with PbCO₃ was developed in this work. The S originally present in ZnS can be converted into PbS, while the Zn can be converted into Na₂Zn(OH)₄ in the alkaline solution in the presence of PbCO₃. And then, the Pb in PbS deposited in the leach residues can be converted into PbCO₃ again in the Na₂CO₃ solution. It was found that over 90% of Zn can be extracted from ZnS when the leaching process is operated in 6 mol/L NaOH solution at 90 °C with PbCO₃ as additive, and over 95% of PbS in the leach residues can be converted into PbCO₃ by stirring the leach residues in Na₂CO₃ solution with air bubble at a temperature of 80 °C. The leaching solution can be used to produce metallic zinc powder by electrowinning after chemical separation of impurities.