The controlled oxidative precipitation of manganese oxides from Mn(II) leach liquors using SO2/air gas mixtures

In the future, an oxidation approach using SO2/O2 could be an important technique for extracting manganese from leach liquors. The aim of this work was to analyse the effect of temperature on the oxidative precipitation of Mn(II) in solutions derived from low-grade ore leaching using a SO2/air gas mixture. This oxidation method is frequently used to eliminate Mn impurities from Ni and Co leach liquors. It was observed that controlling the temperature favoured the selective oxidation of Mn(II) to produce different oxidised species, such as MnO2, α-MnOOH, γ-MnOOH and Mn3O4. The experimental results also showed that higher temperatures promoted the production of species with a lower manganese oxidation state. Moreover, in the range of studied operation variables, it was found that the best oxidation kinetics were obtained at pH = 6, 5% SO2/95% O2 and 75 °C. In addition, for efficiency reasons, a gas mixture flow rate of 200 mL/min is suggested.