Critical role of oxygen for rapid degradation of organic contaminants in permanganate/bisulfite process

Organic contaminants can be oxidized rapidly in permanganate/bisulfite (PM/BS) process due to generation of Mn(III)(aq). However, the influence of O-2 and its role in contaminants degradation in PM/BS process are poorly understood. Thus, the influence of O-2 concentration on phenol removal was quantified and isotopic oxygen tracers (O-18-labeled water and O-18(2)) were employed to further unravel the mechanisms of PM/BS process. The introduction of O-2 to PM/BS process appreciably improved phenol oxidation. Under oxic conditions the oxidation products of bisulfite included SO42- and HSO5- while SO42- was the single stable oxidation product under anaerobic conditions. The oxygen isotope labeling experiments confirmed that HSO5- originated from the oxidation of SO3 center dot- by O-2 to SO5 center dot- and the following reduction of SO5 center dot- by HSO3-. Incorporation of oxygen isotope from (H2O)-O-18 to MnO2 due to the disproportionation of Mn(III)(aq) was observed, which verified the generation of Mn(III)aq in PM/BS process. The critical influence of O-2 on PM/BS process was mainly associated with rapid oxidation of SO3 center dot- by O-2 to SO5 center dot-, which otherwise competed with target contaminants for Mn(III)(aq). Oxygen from H2O and/or O-2 can also be incorporated in the degradation products of organics in PM/BS process.