Fly ash cenospheres supported visible-light-driven BiVO4 photocatalyst: Synthesis, characterization and photocatalytic application

Abstract

A novel BiVO4/Fly ash cenospheres (FACs) composite photocatalyst was prepared by the modified metalorganic decomposition (MOD) method. And the photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectra (XPS), and UV–vis diffused reflectance spectroscopy (DRS) techniques. DRS revealed that the absorption threshold of BiVO4/FACs shifted to a longer wavelength compared with the pure BiVO4 photocatalyst. Adsorption parameters and photocatalytical activity under visible light irradiation were evaluated using the methylene blue (MB) dye as a model. FACs, the solid wastes produced in coal-firing power plants, were used as supports with the advantages of low cost, and also improved the adsorption and photocatalytic activity of BiVO4. The maximum amount of dye adsorbed (Qmax) for BiVO4/FACs is 1.8 times more than that for pure BiVO4, and the photodegradation first-order rate constant for BiVO4/FACs is 2.5 times higher than that for pure BiVO4. Owing to the low density of FAC, the as-prepared BiVO4/FAC particles float in water to favor phase separation and the recovery of the photocatalyst after the reaction. The recovery test shows that BiVO4/FACs composite was rather stable during the MB photodegradation. Based on electron spin-resonance spectroscopy (ESR) results, a reasonable reaction mechanism has also been proposed.