Chemical oxidation of arsenic in the environment and its application in remediation: A mini review

Arsenic (As) contamination in soil and water poses a serious threat to the ecosystem health and human beings, and is of widespread concern. The main As species found in soil and water are arsenite As(III) and arsenate As(V). Because As(III) is more toxic and often more mobile than As(V), many remediation strategies aim to oxidize As(III) to As(V). In the environment, the reduction of As(V) under anaerobic conditions is mainly mediated by microorganisms, but the oxidation of As(III) under aerobic conditions can be mediated primarily by chemical processes. This article first reviews the existing knowledge on chemical oxidation of As(III) in the environment, with an emphasis on the roles of iron (Fe) and manganese (Mn) oxides. The application of Fe and Mn oxides for the remediation of As-contaminated soil and water is then summarized. The oxidation of As(III) by oxygen is very slow in the absence of catalysts. Many Mn oxides, on the other hand, can efficiently oxidize As(III). Although the oxidation of As(III) by Fe(III) is also slow, this process can be accelerated by light or Fe(II). Iron and Mn oxides are widely used for the remediation of As-contaminated soil and water, with Fe oxides generally acting as absorbents while Mn oxides as oxidants. To better understand and regulate As transformation and transport in the environment, further study is needed on the mechanisms and influencing factors of As(III) oxidation by Fe and Mn oxides, and the development of innovative methods and materials based on Fe and Mn oxides are desired.