Oxytetracycline induced the redox of iron and promoted the oxidation of As(III)

Antibiotics and arsenic are two frequently detected contaminants in soils and waters, both of which have potential threats to human health. There are few studies focusing on the interaction between these two groups of contaminants in the environment. In this study, we found that the presence of oxytetracycline could significantly promote the oxidation of inorganic As(III) to As(V) with trace Fe(III) (10 μM) and H₂O₂ (100 μM) at near natural pH, and OTC was degraded simultaneously. The most possible mechanism was that OTC could complex with Fe(III) and reduce Fe(III) to Fe(II), which further induced the Fenton-like reaction. Furthermore, structural Fe(III) of α-FeOOH and adsorbed Fe(III) of montmorillonite could also induce these reactions, and the oxidation rate of As(III) was higher with Fe(III)-montmorillonite than aqueous Fe(III). Based on this study, the transformation of As(III) and OTC could occur in four natural water samples, including river water, groundwater and livestock wastewaters. The results of this study revealed the overlooked effect of residual tetracyclines antibiotics on the transformation of co-existing As(III) in natural waters and soils, which might greatly reduce the toxicity of As(III) in the environment.