China Nonferrous Metallurgy

In order to improve the efficiency of zinc hydrometallurgy, this paper draws ε-pH diagram and predominant zone diagram of zinc-containing materials through virtual simulation calculation, which lays a theoretical foundation for zinc hydrometallurgical leaching and roasting. The ε-pH diagrams of zinc sulfide ore and zinc calcine containing Fe, Cu, Pb and Cd at different temperatures and the predominant zone diagrams of Zn-S-O ternary system and Zn-Me-S-O quaternary system of zinc sulfide ore were simulated by using FactSage thermodynamic software. The results show that during direct leaching of zinc sulfide ore, the pH value of Zn²⁺ is higher than those of Fe²⁺, Cu²⁺, Pb²⁺ and Cd²⁺; while during hot acid leaching of zinc calcine, the pH value of Fe²⁺, Fe³⁺ and Cu²⁺ is lower than that of Zn²⁺, the pH value of Pb²⁺ and Cd²⁺ is higher than that of Zn²⁺, but the potential of Zn²⁺ is lower than those of Fe²⁺, Cu²⁺, Pb²⁺ and Cd²⁺; comparing the ε-pH diagrams of two different minerals, it can be seen that the Zn²⁺ stable zone in the leaching of zinc sulfide ore is smaller than that in the leaching of zinc calcine, which indicates that the leaching effect of zinc calcine is better, and indirectly explains the reason why zinc sulfide ore needs to be roasted before treatment. The predominant zone diagram of zinc sulfide ore shows that ZnSO₄ begins to be decomposed into ZnO at the temperature of 873K, and Fe in zinc sulfide ore will combine with Zn to form ZnFe₂O₄, which hinders the formation of ZnO, and ZnFe₂O₄ is not easy to leach, which leads to the decrease of zinc leaching rate. Therefore, the formation of ZnFe₂O₄ should be reduced as much as possible during roasting.