Sulphuric Acid Leaching of (from Zinc Electrolysis Anode Slime Using PbS as a Reductant

An investigation into leaching of MnO₂ from zinc electrolysis anode slime in Zhuzhou Zinc smelter in sulphuric acid solution using PbS as a reductant was carried out. The effects of the fineness of PbS particle, the molar ratio of PbS to MnO₂, the molar ratio of H₂SO₄ to MnO₂, the reaction time and temperature etc. on the leaching rate of Mn were discussed in the batch test that used pure PbS as the reductante. The results revealed that the finer the PbS particles were, the more contact area of PbS particles to MnO₂ was, and so the faster the leaching speed of Mn was obtained. The results also showed that the molar ratio of PbS to MnO₂, the molar ratio of H₂SO₄ to MnO₂, the reaction time and temperature etc. had significant influence on the leaching speed of Mn. The optimal leaching conditions were obtained using 0.5 molar ratio of PbS to MnO₂ and 3 molar ratio of H₂SO₄ to MnO₂ for 120min at 90℃. At the optimal leaching conditions using 0.037 ~0.074mm pure PbS as the reductant, more than 85% of Mn leaching rate could be obtained. At the same conditions using PbS flotation concentrates as the reductant, more than 93% of Mn leaching rate could be obtained. The leaching test using PbS flotation concentrate as the reductant showed that the synergistic reductive extraction of ZnS and FeS caused the content of impurities in filtrate be upgraded, as well as the content of Pb in leaching slag be reduced. So that, in order to produce high-purity manganese products using Mn²⁺-containing leaching solution, as well as to facilitate leaching slag into the furnace smelting, it is better to adopt a higher grade flotation concentrate of PbS as the reductant.