Oxidation of S(IV) to S(VI) under Fenton, photo-Fenton and γ-FeOOH photocatalized conditions

Hydrogen sulphite oxidation to sulphate through three different routes was investigated. Fenton and photo-Fenton reactions were used to carry out the oxidation process. γ-FeOOH was also used in order to promote the photocatalytic oxidation of S(IV) species. In all three cases a kinetic model based on an autocatalytic reaction is suggested to account for the experimental results obtained. According to this model the intermediate species HSO5 and/or SO5·, generated during S(IV) oxidation, should be involved in the autocatalytic mechanism.