Mechanochemical leaching of sphalerite in an alkaline solution containing lead carbonate

This study investigates the effect of using mechanical activation on the extraction of zinc from sphalerite in an alkaline solution containing lead carbonate. The combined mechanical activation and chemical leaching in a single operation (mechanochemical leaching) is found to be more effective in comparison with the separate mechanical activation and subsequent chemical leaching. A novel hydrometallurgical process for recovering Zn from sphalerite in alkaline solution via chemical conversion with PbCO3 was developed in this work. In the stirred ball mill, the S originally present in sphalerite can be converted into PbS, while the Zn can be converted into Na2Zn(OH)4 in the alkaline solution in 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 86% of Zn can be extracted from sphalerite when the leaching process is operated in 6 mol/L NaOH solution at 90 °C with PbCO3 as additive, and stainless steel ball of 5 mm diameter as activation medium, the mass ratio of ball to raw materials of 30:1, Pb/ZnS of 0.9:1.