Different Role of Bisulfite/Sulfite in UVC-S(IV)-O2 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 (λex = 266 nm), the signals of SO3•− and eaq− generated by photolysis of sulfite at 266 nm were discerned. Quantum yields for photoionization of HSO3− (0.01) and SO32− (0.06) were also measured. It has been established that eaq− does not react with SO32−, but reacts with HSO3− with a rate constant 8 × 107 M−1s−1.