Preparation of g-C3N4/diatomite composite with improved visible light photocatalytic activity

Abstract

With the aid of mixing melamine and diatomite in hydrochloric acid aqueous solution, g-C3N4/diatomite (CN/DE-X, X = 2, 4, 6, 10, 14, which represented the mass ratio of melamine to diatomite) composites were synthesized by calcining the mixture at 550℃ for 2 h. Samples were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, X-ray photoelectron spectroscopy, nitrogen adsorption–desorption measurement, ultraviolet–visible diffuse reflectance spectrum, and photoluminescence spectrum, etc. Rhodamine B (RhB) was used as trial pollutant to evaluate the photocatalytic activity of CN/DE-X composites. The results reveal that CN/DE-X composite is composed of g-C3N4 and diatomite. The photocatalytic activities of CN/DE-X composites are much better than that of pure g-C3N4 and varied with X. CN/DE-10 composite owns the best photocatalytic property in this study, which prohibited the agglomeration of g-C3N4 and had a specific surface area of 47.03 m2/g. 100 mg CN/DE-10 degraded more than 95% of RhB solution (10 mg/L, 100 mL) in 50 min, and its reaction rate constant was about 6.4 times that of pure g-C3N4. CN/DE-10 presents satisfactory stability and reusability since it degraded 90.01% of RhB molecules after 5 cycles of photocatalytic reaction. The outstanding photocatalytic performance of CN/DE-10 is attributed to the enhanced specific surface area, improved UV–Vis light absorption ability, narrowed band gap, reduced recombination rate of the photo-generated electrons and holes, which are brought about by the evenly anchoring of large amount of g-C3N4 on the surface of diatomite.