Dehalogenation efficiency of the sulfite/UV process

Hydrated electron(e_aq^-) is one of the most reactive reducing species. Based on the production of e_aq^- from the excitation of sulfite by UV irradiation, a sulfite/UV advanced reduction process was proposed for removal of recalcitrant contaminants. The reduction efficiency of recalcitrant halogenated organic compounds (HOCs) by the sulfite/UV system was assessed, by choosing seven haloacetic acids as the target compounds. The influence of substituted halogen type, halogenation degree, and realistic surface water matrix were investigated. Results indicate that the HOCs degradation proceeded via at least two pathways, including direct photolysis and e_aq^--induced reduction. Chemical structure of HOCs determined the efficiency of direct photolysis following the ascending order of Cl^-<Br^-<I^- and halogenation degree of HOCs. The reduction by e_aq^- made major contributions to HOCs dehalogenation having relatively slow direct photolysis kinetics. The mechanism was further discussed. The system was also effective in dehalogenation of HOCs in realistic surface water.