China Nonferrous Metallurgy

A smelting enterprise adopts the technical route of zinc acid leaching slag zinc concentrate synergistic leaching-gas phase sulfidation-high temperature mineralization to treat zinc acid leaching slag. After gas phase sulfidation， valuable metals such as indium and copper in the acid leaching slag are precipitated and enrich in the slag. The solution only contains Zn2 + （ about 90 g/L ） and Fe2 +（ about 25 g/L ）， and zinc and iron need to be separated. In this paper， the solution of co-leaching solution of zinc acid leaching residue and zinc concentrate after gas phase sulfidation （ hereinafter referred to as sulfidation solution ） was taken as the research object. Based on the analysis of the potential-pH diagram of Zn-Fe-S-H2O system， the effects of reaction temperature， time， initial pH of solution and SO4 2- concentration on iron precipitation behavior were investigated， and the quality， phase and microstructure of mineralized iron slag were analyzed. The results show that Fe2O3 has high stability under high acid conditions. When the reaction temperature is higher than 150℃， the complexation and hydration of Fe3+ can be effectively destroyed， and the iron is precipitated in the form of Fe2O3. The solubility of Fe2O3 can be further reduced by increasing the sulfate concentration. Under the conditions of reaction time 4 h， reaction temperature 190℃， initial pH=4 and SO4 2- concentration ＜280 g/L， the removal rate of iron was 89. 19%， and the loss rate of zinc was less than 0. 2%. The effective separation of zinc from the leaching solution of zinc acid leaching residue was realized. The mineralized iron slag contains more than 60% iron with less impurities， and has a dense and fine granular shape， which can be used as a raw material for recovering iron.