Removal of Rare-Scattered Metal Impurities in Zinc Sulfate Solution by Ozone Oxidation

There are abundant strategic rare-scattered metal resources in lead and zinc deposits in China, especially zinc resources in Yunnan province, which are associated with indium (In), selenium (Se), tellurium (Te), etc. Small amounts of these rare-scattered metal ions are dissolved into zinc acidic leaching solutions, and are difficult to remove by conventional zinc powder replacement. They are enriched in the ZnSO₄ solution, which causes serious problems to the zinc electrowinning process such as hydrogen generation, zinc re-dissolution, plate burning, low current efficiency, etc. So, they need to be deeply purified from ZnSO₄ solution. This article used ozone, a strong oxidizing agent, to make oxidative precipitation of the impurities from ZnSO₄ solution. The effects of reaction temperature, ozone flow rate, and residence time on In, Se, and Te removal together with the associated Mn removal and Zn loss were investigated. The ozonation reaction kinetics was evaluated by plotting the negative logarithm of the metals in solution concentration as a function of reaction time. One precipitate prepared at optimized conditions was characterized by XRD, EDS, and SEM to identify the chemical compounds and morphology.