Photocatalytic Degradation of Aqueous Nitrobenzene by Nanocrystalline TiO₂

Abstract

This study investigated the role of the band gap, surface area, and phase composition on the photocatalytic activity of nanocrystalline TiO 2 . Nanocrystalline TiO 2 (8−29 nm) was synthesized by hydrolysis of titanium tetraisopropoxide. The crystalline structure, band gap, and morphology of the nanocrystalline TiO 2 were determined by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and N 2 adsorption (BET) at 77 K, respectively. It is observed that the band gap of the nanocrystalline TiO 2 decreases from 3.29 to 3.01 eV with increasing calcination temperature. The crystallite size of the TiO 2 samples prepared also shows an increase with increasing calcination temperature. The photocatalytic degradation of an aqueous solution of nitrobenzene (50 ppm) was studied using nanocrystalline TiO 2 samples with varying band-gap values, as well as a P-25 Degussa TiO 2 sample for comparison. The initial rate of degradation of nitrobenzene was calculated in each case to evaluate the photocatalytic activity of the catalysts. The enhanced photocatalytic degradation of nitrobenzene was observed by purging air through the solution during photocatalysis.