Reductive leaching of zinc and indium from industrial zinc ferrite particulates in sulphuric acid media

Zinc ferrite is the principal constituent in zinc neutral-leach residue (NLR) which is commonly treated by hot-acid leaching in electrolytic zinc plants. Reductive leaching of zinc ferrite with sphalerite concentrate as a reducing agent was performed. It was found that leaching of zinc ferrite in the presence of sphalerit concentrate was a viable process that effectively extracted zinc and indium and converted Fe3+ into Fe2+ at the same time. Reflux leaching tests by two stages were performed to achieve extractions of 98.1% for zinc and 97.5% for indium, and a Fe2+/Fe3+ molar ratio of 9.6 in leach solution was also obtained. The leaching behaviors of other elements, such as iron, copper and tin were also studied. The results showed that iron and copper were completely leached, whereas tin presented lower extraction values.