Reactions of Ultrasonically Generated Hydroxyl Radicals with Arsenic in Aqueous Environments

摘要

The fate, transport, and toxicity of arsenic are dependent on its oxidation state. Hydroxyl and superoxide anion radicals are formed naturally and may contribute significantly to redox processes of arsenic in the environment. We have studied ultrasonically generated hydroxyl radical with arsenic species in the presence of oxygen and argon over a range of solution pH and arsenic concentrations. As(Ⅲ) reacts via a pseudo-first order process under our experimental conditions. The reaction of hydroxyl radical with As(Ⅲ) likely yields As(Ⅳ), which can react with oxygen to form As(Ⅴ). The transformation rates are different under oxygen versus argon-saturated conditions and at different solution pH values. Although superoxide anion radical can act as a reducing agent and is formed under our experimental conditions, reduction of As(Ⅴ) was not observed. The kinetic parameters determined in these studies may be useful for the development of models to predict the fate, redox conversion, and remediation of these species in aquatic environments.