Mechanochemical leaching of Zn from low-grade smithsonite using Fe2(SO4)3 solution

Abstract

Herein, the first-ever use of Fe2(SO4)3 solution as a leaching reagent to leach Zn from smithsonite under mechanical activation is reported. Thermodynamic calculations demonstrate that the leaching reaction's Gibbs free energy change is negative at ambient temperature and pressure (298.15 K, 100 kPa), implying the thermodynamic spontaneity and feasibility of the reaction. The feasibility assessment of leaching confirmed that ZnCO3 can be converted to water-soluble ZnSO4 through a near-stoichiometric reaction with Fe2(SO4)3 solution. Furthermore, X-ray diffraction analyses show that Fe3+ ions precipitate into the leaching residues in the form of an amorphous phase. Leaching experiments with low-grade smithsonite are performed to determine the leaching effect of natural smithsonite ore using Fe2(SO4)3 solution. Optimum conditions (the Fe/Zn molar ratio: 1.4, the rotational speed of the planet carrier comprising the mill: 300 rpm, the mechanochemical leaching time: 60 min, the liquid–to–solid ratio 1–10 mL·g−1) yielded a leaching efficiency of 99.6%. The proposed process provides a new simple approach for extracting Zn from carbonate-type Zn oxide ores.