Arsenic(III) and iron(II) co-oxidation by oxygen and hydrogen peroxide: divergent reactions in the presence of organic ligands

Iron-catalyzed oxidation of As(III) to As(V) can be highly effective for toxic arsenic removal via Fenton reaction and Fe(II) oxygenation. However, the contribution of ubiquitous organic ligands is poorly understood, despite its significant role in redox chemistry of arsenic in natural and engineered systems. In this work, selected naturally occurring organic ligands and synthetic ligands in co-oxidation of Fe(II) and As(III) were examined as a function of pH, Fe(II), H2O2, and radical scavengers (methanol and 2-propanol) concentration. As(III) was not measurably oxidised in the presence of excess ethylenediaminetetraacetic acid (EDTA) (i.e. Fe(II):EDTA