Thermodynamics of leaching roasted jarosite residue from zinc hydrometallurgy in NH4Cl system

The thermal decomposition process of jarosite residue and the solubility of various oxides presented in the decomposed residue in NH4Cl-H2O system were studied. The results of heat decomposition of jarosite residue show that the insoluble ZnFe2O4 phase in the residue can be decomposed at temperatures ranging from 500 °C to 650 °C for 1 h. The OLI Systems software was used to study the thermodynamics of the solubility of various metal oxides existing in the decomposed residue in NH4Cl-H2O system. The results show that the solubility of ZnO, PbO, CdO, CuO and Ag2O is high, while the solubility of Fe2O3 is less than 10−4 mol/L in the pH range from 4.0 to 9.0. The calculated data are in accordance with the experimental results.