FeOOH modified carbon doped TiO2 p-n heterojunction wrapped Fe3O4 for highly efficient removal of As(III) through photocatalytic oxidation and adsorption

Arsenic pollution control of wastewater is still a difficult problem in environmental governance. In this paper, a bifunctional p-n heterojunction for removing As(III) has been constructed by FeOOH modifying carbon-doped TiO2, which can achieve highly efficient photocatalytic oxidation of As(III) and synchronous adsorption of the generated As(V). Furthermore, the Fe3O4 cores were wrapped by the p-n heterojunction (FeOOH@C/TiO2@Fe3O4) to realize the recycling of photocatalysts through magnetic separation. A series of characterizations showed that carbon doping and FeOOH modifying could promote the light energy utilization of TiO2 and boost the separation efficiency of photogenerated carriers through interfacial chemical bonds and built-in electric fields, facilitating the visible photocatalytic oxidation of As(III). Simultaneously, the presence of FeOOH on the surface of heterojunction can efficiently adsorb the generated As(V) through forming Fe − O − As bonds. As a result, the FeOOH@C/TiO2@Fe3O4 heterojunction (20 mg) can completely remove 10,000 μg·L−1 (40 mL) of As(III) from water within 12 min. Additionally, The reusability of FeOOH@C/TiO2@Fe3O4 is outstanding, maintaining 100 % As(III) removal even after 5 cycles without significant changes in its crystal structure. The superior photocatalytic oxidation and adsorption properties of FeOOH@C/TiO2@Fe3O4 indicate that it is an effective approach to remove arsenic by constructing bi-functional heterojunction.