Characterization and Process Development for Leaching Residues

Currently, Zinc is mainly produced via the hydrometallurgical route, generating huge amounts of iron precipitation residues. These materials are mainly dumped, due to missing economic treatment options. For the development of possible processes, detailed knowledge of the materials characteristics is mandatory. Beside chemical composition, mineralogical characterization is of importance to identify present phases containing valuable components. University of Leoben has a special focus on such precipitation residues with the aim to develop guidelines how to evaluate such materials which show a certain challenge, especially because of the fineness of the residue. Nevertheless, it has been found at many sites worldwide that, depending on the primary zinc winning process, interesting values of lead, zinc and silver are present, turning the waste into an interesting secondary resource. Various methods (XRF, ICP, XRD etc.) have been used for chemical analysis and the identification of major phases. Scanning electron microscopy is an appropriate choice for the definition of minor phases and chemical analysis of single grains. The successful characterization of such materials forms the base for different processing concepts to utilize currently unused secondary resources.