Oxidation of methylated arsenic species by UV/S2O82-

Abstract

UV/S2O82- process was studied for the oxidation of monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in aqueous solution. UV/H2O2 and UV/TiO2 were also applied to the oxidation of the target compounds. TiO2 was added at a low dosage (50 mg/L), considering a condition advantageous for catalyst separation. Under the experimental condition of this study ([S2O82-](0) = [H2O2](0) = 1 mM, [TiO2](0) = 50 mg/L), UV/S2O82- was more effective for oxidizing MMA and DMA than UV/H2O2 and UV/TiO2. The oxidation rate of DMA by UV/S2O82- could be accelerated by increasing the ratio of [S2O82-]/[DMA]. The oxidation efficiencies of MMA and DMA by UV/S2O82- were lower at initial pH 7 than at initial pH 3 and 10. This phenomenon was attributable to the radical-scavenging effect of bicarbonate, which was added as a pH-buffering solute. The results shown in this study show that UV/S2O82- is an effective oxidation process for MMA and DMA. (C) 2011 Published by Elsevier B.V.