Optimization of photocatalytic degradation of bisphenol A by novel Bi2O3–TiO2 nano-composites under visible light irradiation

A series of Bi–Ti composited photocatalysts with different molar ratio of Bi/Ti (0.01:1(1%), 0.02:1(2%), 0.04:1(4%), and 0.05:1(5%)) and calcination temperature (400°C, 500°C, and 600°C) were prepared by sol-hydrothermal method. The properties of as-prepared photocatalysts were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photo-electron spectroscopy, Brunauer–Emmett–Teller, and ultraviolet–visible diffuse reflection spectroscopy. The selected photocatalyst (Bi-Ti-4%-600°C) was prepared under Bi/Ti molar ratio of 4% and calcination temperature of 600°C. Experimental variables during photocatalytic degradation were optimized for catalyst dosage, solution pH, initial bisphenol A (BPA) concentration, coexisting anions, and light source wavelength. Under optimal conditions of 1.0 g L –1 catalyst, pH 3, 30 mg L –1 initial BPA concentration, the degradation rate of BPA could reach up to 100% at 150 min under visible light irradiation. Compared with self-made pure TiO 2 and commercially available P 25 , Bi-Ti-4%- 600°C displayed an excellent photocatalytic activity for BPA degradation. Bi-Ti photocatalyst had a smaller crystal size, larger specific surface area, stronger visible light absorption ability, and lower band gap energy than self-made pure TiO 2 . Four intermediates of BPA degradation were identified and a possible degradation pathway was proposed.