Rapid visible light catalytic reduction of Cr(VI) over amorphous g-C3N4 modified palygorskite composite via a charge-transfer-surface complex-mediated pathway

A simple method of high-temperature calcination was used to construct palygorskite/g-C3N4 composite photocatalysts. The as-prepared composites were characterized by X-ray diffractions, Fourier transform infrared spectrum, UV-vis diffused reflection spectra, specific surface area, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The photocatalytic activities were evaluated by Cr (VI) reduction efficiency in the presence of tartaric acid under visible light illumination. The results showed that the PAL/g-C3N4-4 sample exhibited enhanced visible light photocatalytic performance, which is due to increased light absorption, specific surface areas and close interfacial contact between g-C3N4 and PAL. Charge-transfer-surface complex-mediated pathway was proposed for the Tar-induced photocatalytic reduction mechanism of Cr (VI). Because of the existence of N vacancies, the surface of prepared PAL/g-C3N4 -4 composite is positive charged. The endogenous positive charge surface of PAL/g-C3N4-4 sample is not only conducive to the formation of charge-transfer-surface complex, but also conducive to wide pH range application. Additionally, the reusability and stability of PAL/g-C3N4-4 sample were measured by successive recycling tests and XRD analysis, respectively.