Recovery of zinc from leach residues-problems and developments

Abstract

In the hydrometallurgical treatment of sphalerite concentrations, the preroasting step before leaching leads to the tie up of Zn in the form of zinc ferrite, which amounts to significant metal losses since it is insoluble in dilute sulphuric acid. Considering the tonnages of leach residue dumped every day at the plant site, the lost Zn values could assume gigantic proportions, as it is estimated that typical leach residues analyse up to 18% Zn. The processes that have been developed to tackle the problem due to zinc ferrite formation are described.