Abstract:To address narrow roasting temperature range and difficulty of industrial application of original combined process of “zinc slag roasting, acid leaching of indium and zinc, chloride leaching of silver and lead” in treating jarosite slag from zinc hydrometallurgy, a new process of “jarosite slag roasting, acid leaching, iron removal from acid leaching solution with phosphoric acid and produce byproduct of ironic phosphate, extracting indium and zinc after iron removal” was put forward. The process to remove iron from acid leaching solution of jarosite slag by phosphoric acid was studied, in terms of technological conditions, law of kinetic and phase of by-product of ferric phosphate. The results show that the optimum conditions for iron removal include P/Fe=0.9, temperature of 85 ℃, time of 8 h, and inducer dosage of 0.7 g, under which, iron removal rate is 58.08% and indium loss rate is 26%, Fe leaching rate in jarosite slag is reduced from 23% to 9.66% (≤10%), indium leaching rate after iron removal is 70.3% (≥70%), and loss rate of Zn2+ in acid leaching solution is very small. The leaching rates of three elements all meet the requirements of the index. Iron removal and indium loss during iron removal with phosphoric acid basically accord with zero order reaction with activation energy of 51.25 kJ/mol and 46.12 kJ/mol, respectively. High purity crystalline FePO4?2H2O is by-product. The roasting temperature range of jarosite slag is 70 ℃.