Simultaneous photocatalytic oxidation and adsorption for efficient As(III) removal by magnetic BiOI/γ-Fe2O3 core-shell nanoparticles

Addressing arsenite pollution in groundwater has drawn great attention. It is attractive to pre-oxidize highly mobile As(III) to relatively low-toxic As(V) with a subsequent adsorption separation process. Herein, BiOI anchoring on gamma-Fe2O3 is performed to synthesize BiOI/gamma-Fe2O3 core-shell nanoparticles for efficient removal of As(III) via a simultaneous photocatalytic oxidization-adsorption process. The physical and chemical structures of BiOI/gamma-Fe2O3 are investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction measurements. The photoluminescence and electron spin resonance (ESR) characterization were employed to ascertain the possible reaction mechanism of visible-light-driven photocatalytic oxidation of As(III). Such BiOI/gamma-Fe2O3 delivers a superior As(III) removal capability under visible light irradiation with an arsenic removal efficiency of 99.8% within 180 min, higher than those of BiOCl/gamma-Fe2O3 (81.7%) and BiOBr/gamma-Fe2O3 (98.9%). The optimal BiOI/gamma-Fe2O3 (molar ratio of 2:1) is obtained by rationally adjusting the molar ratio of BiOI to gamma-Fe2O3. The as-synthesized BiOI/gamma-Fe2O3 performs well in a wide pH range of 2-8. Only coexisting PO43 anions have a significant effect on the As(III) removal. The free radical trapping experiment and ESR results demonstrate that the center dot O-2(-) and h(+) are the main active substances for the photocatalytic oxidation of As(III) on BiOI/gamma-Fe2O3. This work not only gives a novel magnetic core-shell nanoparticle photocatalyst for efficient photocatalytic oxidation and adsorption of As(III) but also offers a new strategy to rationally design BiOX for its related practical applications. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

This study focuses on the efficient removal of arsenite pollution in groundwater using BiOI/gamma-Fe2O3 core-shell nanoparticles as photocatalysts. The optimal molar ratio of BiOI to gamma-Fe2O3 is found to be 2:1. The main active substances for the photocatalytic oxidation of As(III) on BiOI/gamma-Fe2O3 are identified as ∙O2- and h+.