Effect of synthesis temperature on the structural properties and photocatalytic activity of TiO2/SiO2 composites synthesized using rice husk ash as a SiO2 source

TiO2/SiO2 composites were synthesized using titanium tetrachloride as a TiO2 precursor and rice husk ash (RHA) as the SiO2 source at low temperatures. Their photocatalytic performances were investigated in the liquid phase degradation of terephthalic acid (TPA) under UV-C illumination. The effect of synthesis temperature on the properties and photocatalytic activities of the composites were examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission gun scanning electron microscope (SEM), thermo gravimetric analysis (TGA), N-2 adsorption desorption analysis, and UV-visible diffuse reflectance spectroscopy (UV-DRS). The XRD patterns indicated the synthesis of rutile TiO2 particles due to the acidic nature of the reactant solution at low temperature without the need of calcination. The SEM images showed that the spherical and flower like agglomerates, consisting of nano fibers, are formed depending on the synthesis temperature. The TGA analysis showed no structural change or deformation in the catalysts due to heating. The N-2 adsorption desorption analysis revealed a change in the pore structure of the TiO2 particles from micro-to mixed micro-and meso-porous in the TiO2/SiO2 composites with an increase in their surface areas. The differences in the structural properties of the composites varied their photocatalytic activities in the degradation reactions. The presence of SiO2 in the composites enhanced the photocatalytic activity of the TiO2 particles and simplified the recovery of the catalysts from the treated solution by increasing their rate of precipitation. The TiO2/SiO2 composites synthesized at 95 degrees C exhibited the best photocatalytic activity confirmed by both kinetic constant and turnover frequency. All the particles and composites synthesized indicated better photocatalytic performance than that of the P25 TiO2. (C) 2014 Elsevier B.V. All rights reserved.