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 (lambda(ex) = 266 nm), the signals of SO3 center dot- and e(aq)(-) 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 e(aq)(-) does not react with SO32-, but reacts with HSO3- with a rate constant 8 x 10(7) M(-1)s(-1).