Synthesis of Mesoporous TiO2 Template-Free and Photocatalytic Activity for Azo Dye Degradation

Abstract

Nanoporous titanium dioxide was prepared by sol-gel technique. To control the surface area, pore size and pore volume of the prepared TiO₂, a catalyzed hydrolysis was carried out using different concentrations of silicotungstic acid (SWA) as a template. A fixed molar ratio of H₂O/Ti was used. The prepared TiO₂ was calcined at 400 or 600^oC. Samples were characterized by nitrogen physic-sorption, X-ray powder diffraction (XRD), selected scattered electron diffraction, Raman spectroscopic analysis, Fourier Transform spectroscopy (FTIR), Thermo gravimetric analysis (TGA), Differential scanning calorimetry (DSC), scanning and transmission electron microscopy (SEM and TEM). The photocatalytic activity of the prepared samples was evaluated by the degradation of alizarin yellow under UV light. The results showed that the crystallinity increases as the concentration of SWA decreases. The presence of SWA during the precipitation of TiO₂ prevents the formation of rutile phase and suppresses the crystal growth. The results showed also that the surface area increases as the concentration of SWA decreases. The samples prepared using 0.05M SWA and calcined at 600 ^oC showed a higher activity.

Keywords: mesoporous TiO₂, photocatalytic degradation, alizarin yellow, azodye.