Application of zinc ferrite reduction in the extraction of Zn, Ga and In from zinc refinery residue

Abstract Extraction of gallium and indium from zinc refinery residue (ZRR) has continued to attract attention because of different mineralogy of residues and occurrences of trace elements in ZRR. About 90% of gallium is currently extracted from Bayer liquor, whereas, ZRR has been a primary source for indium recovery. The primary production of gallium and indium in USA is currently zero. However, zinc residues are a promising resource for the extraction of critical metals such as gallium, germanium and indium. The major problem in ZRR is the concentration of zinc ferrite (ZF) which is refractory to leaching. The current study introduces a method to enhance the leaching kinetics of ZRR having ZF as major constituent. In this study, ZF was partially reduced with reducing gas containing 10% H2 and the roasting product was then leached under different conditions. The effect of reduction roasting was found to have a significant impact on the leaching kinetics of ZRR. The decomposition of ZF eased the leaching of zinc, gallium and indium. More than 90% extraction of the target elements was achieved with this process. The manuscript also discusses the characterization of ZRR using laser ablation inductively coupled plasma-mass spectrometry (LA ICP-MS), scanning electron microscopy (SEM), x-ray diffraction (XRD) and automated mineralogy.