Different Role of Bisulfite/Sulfite in UVC-S(IV)-O(2) System for Arsenite Oxidation in Water

It is of interest to use UV-sulfite based processes to degrade pollutants in wastewater treatment process. In this work, arsenic (As(III)) has been selected as a target pollutant to verify the efficacy of such a hypothesized process. The results showed that As(III) was quickly oxidized by a UV-sulfite system at neutral or alkaline pH and especially at pH 9.5, which can be mainly attributed to the generated oxysulfur radicals. In laser flash photolysis (LFP) experiments (λ(ex) = 266 nm), the signals of SO(3)(•−) and e(aq)(−) generated by photolysis of sulfite at 266 nm were discerned. Quantum yields for photoionization of HSO(3)(−) (0.01) and SO(3)(2−) (0.06) were also measured. It has been established that e(aq)(−) does not react with SO(3)(2−), but reacts with HSO(3)(−) with a rate constant 8 × 10(7) M(−1)s(−1).