One-Pot Synthesis of a Magnetic TiO2/PTh/γ-Fe2O3 Heterojunction Nanocomposite for Removing Trace Arsenite via Simultaneous Photocatalytic Oxidation and Adsorption

Arsenic pollution has drawn wide attention, owing to its severe carcinogenicity, strong poisonousness, and high mobility in groundwater. Herein, a magnetic heterojunction nanocomposite of TiO2/polythiophene/γ-Fe2O3 (TiO2/PTh/γ-Fe2O3) was fabricated by one-pot oxidation polymerization as a novel photocatalyst for removing trace As(III) from aqueous solution by a visible-light-driven photocatalytic oxidation–adsorption coupling process. The nanocomposite showed excellent stability to adsorb As(III) in a low-pH region (2–6). Under dark conditions, approximately 46.5% of As(III) was adsorbed by the as-synthesized nanocomposite, and the kinetic data indicated the dominating chemical adsorption. However, under visible light illumination, more than 99.1% of As(III) was transformed into As(V) and simultaneously 90.1% of produced As(V) was adsorbed by the nanocomposite. Furthermore, the photogenerated holes (h+) and superoxide free radicals (•O2–) were the main reactive substances on the TiO2/PTh/γ-Fe2O3 nanoparticle for visible-light-driven photocatalytic oxidation of As(III). The novel magnetic TiO2/PTh/γ-Fe2O3 heterojunction nanocomposite may have potential application for arsenic removal in the aquatic environment.