Rapid TiO2/SBA-15 synthesis from ilmenite and use in photocatalytic degradation of dimethoate under simulated solar light

Abstract

SBA-15 mesoporous materials loaded with 8%–42% TiO2 were prepared by post-synthesis hydrolysis using ilmenite as the TiO2 source. X-ray diffraction, high-resolution transmission electron microscopy, nitrogen adsorption–desorption measurements, and Fourier-transform infrared, X-ray photoelectron, Raman, and ultraviolet-visible spectroscopies were used to investigate the TiO2/SBA-15 morphology and crystal structure. The results show that TiO2 was successfully loaded on the mesoporous SBA-15 and the highly ordered two-dimensional hexagonal structure was stable. The photocatalytic performances of the samples in dimethoate degradation under simulated solar light were investigated. The photocatalytic activity initially increased and then decreased with increasing TiO2 loading. The 26% TiO2/SBA-15 sample showed the highest photocatalytic activity and completely degraded dimethoate within 7 h. The catalytic activity of TiO2/SBA-15 was 62% higher than that of pure TiO2. This may be because of a synergistic effect resulting from the adsorption of dimethoate on the mesoporous material. The presence of Ti–O–Si species enhances the TiO2 surface acidity and formation of surface adsorption sites; The adsorption and electron delocalization properties of SBA-15 are the main reasons for the observed enhancement of the pesticide degradation rate. These improves the TiO2/SBA-15 photocatalytic activity. TiO2/SBA-15 maintained high photocatalytic activity and good stability during four cycles, with a dimethoate degradation rate greater than 94%. The byproducts generated during photocatalysis were identified using gas chromatography-mass spectrometry. The photocatalytic degradation of dimethoate followed first-order kinetics. The mechanism of the photocatalytic degradation of dimethoate was investigated.