Synthesis of titanium dioxide supported on mesostructured silica nanoparticles for photocatalytic decolourization of congo red

Abstract

Various dyes that had been widely used in industries may produce harmful effects to the living organisms and the environment if not treated properly before being discharged into water bodies. Photocatalytic decolourization is one of the promising techniques to degrade dyes due to its mild operating conditions and green technology process. In this study, the effects of titanium dioxide (TiO2) supported on mesostructured silica nanoparticles (MSN) under different preparation methods were investigated for photocatalytic decolourization of congo red (CR). The microwave-synthesized mesoporous titania nanoparticles (MTN) supported on MSN were prepared by impregnation method (MTN/MSN), while electrogenerated TiO2 was supported on MSN by in-situ electrochemical (TiO2/MSN-E) and impregnation (TiO2/MSN-I) methods, respectively. The properties of the catalysts were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Nitrogen adsorption-desorption, electron spin resonance (ESR) analysis and 29Si magic angle spin nuclear magnetic resonance (29Si MAS NMR). The results indicated that the introduction of MTN and TiO2 did not change the lattice structure of MSN but decreased the surface area and pore volume of the catalysts as a consequence of pore blockage. The photocatalytic activity of the catalysts towards decolourization of 10 mg L-1 CR at pH 5 with 1.0 gL-1 catalyst after 5 h was in the following order: TiO2/MSN-E > MTN/MSN > TiO2/MSN-I. The TiO2/MSN-E (94 %) showed the best performance compared to other catalysts, probably due to the presence of abundant Si-O-Ti bonds oxygen vacancies and titanium site defect in MSN frameworks. The kinetics study of the catalysts indicated that decolourization of CR followed the pseudo first order Langmuir-Hinshelwood model. The response surface methodology study for TiO2/MSN-E catalyst demonstrated good significance of model with a high coefficient of determination (R2 = 0.9698) and a regenerated study showed that the catalysts were still stable after 5 cycles. The employment of the catalyst on decolourization of simulated dyes revealed remarkable performance, suggesting the potential use of the catalysts for textile wastewater treatment.