The paper presents a study of sulphatizing roasting using iron (II) and (III) sulphates of copper slag flotation tailings of JSC “SUMZ” (Sredneuralsk Copper Smelter) with high content of silica. Temperature ranges of sulphatizing roasting and necessary amounts of Fe2(SO4)3 and FeSO4 for sulphation of zinc and copper were calculated by thermodynamic software HSC Chemistry 9.9. The laboratory experiments have shown that the degree of extraction of zinc and copper from the roasted samples during water leaching is in the range of 60-79%, while the degree of dissolution of iron is less than 1.1%. The obtained results are better or comparable to the results of direct leaching of copper tailings by strong sulfuric acid.

The paper presents the results of the investigation of zinc leach residue (ZLR) processing by sulphatizing roasting with iron sulphates FeSO4 and Fe2(SO4)3 followed by water leaching. The elemental and phase compositions of ZLR of JSC "Chelyabinsk Zinc Plant" were studied. Based on the thermodynamic calculations using HSC Chemistry 9.9 software, the temperature ranges of the sulphatizing roasting and the required amounts of iron sulphate additives for the sulphation of zinc and copper were determined. Subsequent experiments showed that recovery rates of zinc and copper reached 99.5% and 89.1% respectively, while iron remained in the leached residue. The results have indicated a high efficiency of sulphatizing roasting to transform zinc and copper contained in ZLR from ferrite to water-soluble sulphate.