Photocatalytic degradation of organic dyes in the presence of nanostructured titanium dioxide

Titanium dioxide photocatalyst was synthesized through a low temperature co-precipitation process using TiCl4 as a precursor for degradation of Rhodamine B (RB) Acid Red 57 (AR57) and under UV irradiation. The activities of the photocatalyst prepared at calcination temperature 400, 500 and 600 °C were investigated. The resultant TiO2 photocatalyst was characterized by different techniques, such as XRD, SEM, EDX, N2 adsorption and titration for the determination of the zero point charge (pHZPC). It has been found that 400 °C annealed sample of TiO2 exhibits the highest photocatalytic dye degradation efficiency of 93.8 and 90.7% for RB and AR57, respectively within 190 min. The effect of operation parameters such as pH, catalyst dosage, initial dye concentration, as well as the influence of calcination temperatures was evaluated. Results showed that the degradation rate of dyes increased with the increased dosage of TiO2 catalyst and decreased initial concentration of the dye. Furthermore, the kinetics and scavengers of the reactive species during the degradation were also studied. It was found that the degradation of RB and AR57 fitted the first-order kinetics and OH• radicals were the main species. Formation of OH• free radicals during irradiation is determined by photoluminescence studies using terephthalic acid as probe molecule.