Oxidative ammonia leaching kinetics of zinc extracted from mixed sulfide-oxide lead and zinc ore

The leaching experiments of zinc from mixed sulfide-oxide lead and zinc ore were performed in NH₃-(NH₄)₂SO₄ solution with ammonium persulfate as an oxidant under atmospheric pressure and relatively low temperature. The effects of stirring speed, lixiviants, oxidant concentration and reaction temperature on the leaching rate of zinc were studied. The results show that under the optimal conditions, the leaching rate of zinc can reach 93. 2%, and nearly no other metal ions enter into lixivium during the leaching process, which shows that this ammoniacal leaching system has a high efficiency and selectivity. This is significant to simplify the following purification process and product preparation process. Leaching kinetics indicates that the oxidative leaching of zinc could be represented by a shrinking core model with product layer diffusion and the activation energy for the dissolution reaction is calculated as 17. 89 kJ·mol^-1.