SO2/O2 as an oxidant in hydrometallurgy

Oxygen mixed with SO2 can function as a powerful oxidant in acid solution. This paper summarises basic studies on the mechanism of SO2/O2 oxidation, the kinetics of oxidation in acidic media, and potential applications in hydrometallurgy. The SO2/O2 system readily oxidises Fe(II) to Fe(III) and provides a simple method of regenerating Fe(III) for leaching minerals like Cu2S or U3O8. It also oxidises As(III), which in the presence of iron(III) enables a stable ferric arsenate compound to be precipitated. A method for the leaching and removal of arsenic from smelter fumes is proposed. Oxidation of Mn(II) to Mn(III)/Mn(IV) oxides by SO2/O2 allows manganese impurity to be removed from leach liquors and electrolytes.