SELECTIVE LEACHING OF LEAD FROM A LEAD-SILVER-ZINC CONCENTRATE WITH HYDROGEN PEROXIDE IN CITRATE SOLUTIONS

摘要

Selective leaching of lead from a Pb-Ag-Zn concentrate with hydrogen peroxide in citrate solutions was studied at room temperature. Leaching tests were performed, varying the H_2O_2 concentration and the solid-liquid ratio, holding the solution pH constant at 7, and the citrate concentration at 1 M. Lead extractions of 100 % were achieved with 4 and 5 times the stoichiometric quantity needed to form elemental sulfur, with only a small amount of metal impurities dissolved (Ag, Zn and Fe). The lead solubility limit at those conditions was found to be -21 gL~(-1). X-ray diffraction analyses of the leach residues were free of galena (PbS), while other metal sulfides, such as sphalerite (ZnS), chalcopyrite (CuFeS_2) and pyrite (FeS_2), were basically unaffected.