The Oxidation and Immobilization of As(III) by Colloidal Ferric Hydroxide in the Concomitant Pollution of Oxytetracycline

The concomitant pollution of arsenic and antibiotics has commonly occurred in the environments recently, the behaviors of which may be different from single existence. Colloidal ferric hydroxide (CFH) is ubiquitous, existing in surface waters, seawaters, sediments, and paddy soils. In this study, the interaction between oxytetracycline (OTC) and CFH facilitated OTC degradation and reduced Fe(III) to Fe(II). In oxic conditions, the reactions between dissolved oxygen (DO) and Fe(II) generated reactive oxygen species (ROS). •OH and O2•– were the main free radicals through electron paramagnetic resonance (EPR) measurement, and 8.1 ± 0.5 μM •OH was detected after 48 h of reaction. Quenching experiments indicated that •OH had dominated the oxidation of As(III). Furthermore, ferric arsenate formed after the oxidation of As(III) to As(V), which greatly decreased As(III) risks in the environment. The transformation of As(III) was also observed with other iron oxides or different antibiotics. The results of this study proved the facilitation of residual antibiotics in the redox process of iron oxides and transformation of co-existing pollutants, which extended our understanding on the roles of organic pollutants in combined contamination