Comprehensive Study on the Mechanism of Sulfating Roasting of Zinc Plant Residue with Iron Sulfates

Zinc plant residue (ZPR) is a secondary material generated during hydrometallurgical zinc production that contains considerable contents of valuable elements such as Zn, Cu, Fe, Pb, Cd, Ag, In, Ga, Tl. Zinc, copper and accompanying elements in ZPR are in different minerals, mainly in the ferrites. A promising approach for recycling ZPR is the sulfating roasting using iron sulfates followed by water leaching. In this study, the composition of ZPR and the obtained products were thoroughly investigated by various methods including X-ray diffraction analysis (XRD), chemical phase analysis and Mossbauer spectroscopy. The effect of temperature, amount of iron sulfates and roasting time on the conversion of valuable metals into a water-soluble form was thermodynamically and experimentally studied both using pure ferrites and ZPR. Based on the results of time-resolved XRD analysis and synchronous thermal analysis (STA), a mechanism of the sulfation roasting was elucidated. The rate-controlling step of zinc and copper sulfation process during the ZPR roasting was estimated. The sulfating roasting at 600 degrees C during 180 min with the optimal Fe-2(SO4)(3)center dot 9H(2)O addition followed by water leaching enables to recover 99% Zn and 80.3% Cu, while Fe, Pb, Ag, In, Ga retained almost fully in the residue.

Automated summary

The study comprehensively investigated the composition of Zinc plant residue (ZPR) and the obtained products using various methods, elucidated the mechanism of sulfating roasting, and estimated the rate-controlling step of zinc and copper sulfation process. The results showed that the optimal condition for recovery of 99% Zn and 80.3% Cu is sulfating roasting at 600 degrees C for 180 min with the Fe-2(SO4)(3)center dot 9H(2)O addition, followed by water leaching, while Fe, Pb, Ag, In, Ga retained almost fully in the residue.