Abstract
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.
Highlights
Advanced oxidation processes (AOPs) using sulfite (S(IV)), as effective strategies for the removal of contaminants, have attracted a lot of attention [1,2,3]
We found that alkaline solution strongly facilitated As(III) oxidation from only 23% at pH 7 to 72% at pH 9.5 within 10 min
These results demonstrated that oxysulfur radicals generated in the UVC-sulfite system were the main reason for As(III) oxidation
Summary
Advanced oxidation processes (AOPs) using sulfite (S(IV)), as effective strategies for the removal of contaminants, have attracted a lot of attention [1,2,3]. Many As(III) oxidation processes have been devised, such as direct photolysis [16,17] and homogeneous or heterogeneous metal-sulfite systems [2,18,19,20]. The former is time-consuming while the latter introduces secondary pollution in the form of the metal in the metal-S(IV) systems. As(III) is much more toxic than inorganic As(V) and accounts for about 20% of the arsenic present in the natural environment [21]. Laser flash photolysis has been utilized to obtain the quantum yields of photolysis of S(IV) species under 266 nm irradiation and the rate constant for the reaction between eaq − and S(IV)
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