A novel layer-layer crossed structure of bentonite/g-C3N4 for enhanced photocatalytic oxidation of arsenic(III) in a wide pH range

In this work, a novel 2-dimentional (2D)-2D bentonite/g-C 3 N 4 composite (B/g-C 3 N 4 ), with a layer-layer cross structure and large surface area, was synthesized by a self-assembly process, with the aim for the photocatalytic oxidation of arsenic (As(III)) in wastewater. The structure and properties of the mineral-based composite were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), and photocurrent measurements. The photocatalytic activity of 2D-2D B/g-C3N4 for As(III) removal was further investigated under visible light . The results reveal that the As(III) oxidation rate by 2D-2D B/g-C3N4 composite was three times higher than that by pure g-C3N4, owing to the enlarged specific surface area and the suppressed electron–hole recombination by the incorporated bentonite. Moreover, the composite exhibited a high photocatalytic oxidation efficiency in a wide pH adaptability from 3 to 8.5. Through electron spin resonance (ESR) technique and radical quenching experiments, the photocatalytic mechanism of As(III) oxidation was proposed, where superoxide radicals played a critical role in the photo-oxidation of As(III) in both acid and basic conditions. This work paved a new way to design the mineral-based photocatalyst for treatment of pollutants in a wide pH range.