Arsenite Oxidation by Ultrasound Combined with Ultraviolet in Aqueous Solution

Abstract

This study aims to investigate the sonophotochemical oxidation of As(III) to As(V) using the synergistic effect of a strong oxidant that is a hydroxyl radical. The rate constant, k, in the ultrasound (US), ultraviolet C (UV-C), and US/UV-C processes was found to be 1.65 x 10(-4), 3.65 x 10(-4), and 8.31 x 10(-4) s(-1) respectively. The highest power densities were 21.26, in the case of UV-C, and 26.27 W L-1 for US. Finally, the combined US/UV-C system gave a synergistic effect value of 1.57. This was similar to the synergistic effect value of the production of hydroxyl radicals with potassium iodide (KI) solution using the same combined process. Moreover, the reaction rate of the As(III) oxidation to As(V) in the US/UV-C process increased with a gradual increase in pH. The reaction rates were found to be 1.88 x 10(-3) at pH 11 and 8.31 x 10(-4) s(-1) at pH 7. Therefore, the reaction rate at pH 11 was 2.3 times faster than that at pH 7. (C) 2012 The Japan Society of Applied Physics