Abstract: By changing initial concentration,reaction temperature,pHand irradiation time,the photocatalytic selective oxidation of SO₂ aqueous solution is investigated.The experimental results show that both percentage oxidation of SO₃^2- and selectivity of S₂O₆^2- dithionate are closely interrelated and assumption on the role of intermediates,atomic hydrogen H,which was produced prior to H₂ formation,photospillover and participation in the mediated reduction of SO₄^2- to form S₂O₆^2-,has been verified.In optimal conditions of H·formation,0.05 mol/L,80℃,pH 8.8 and irradiation time 4 h,the selectivity of the expensive S₂O₆^2- can be increased to 59.3% as the first oxidation product.

Key words: Sulfur dioxide, Photocatalysis, Selective oxidation, Hydrogen transfer, Photospillover