Degradation of p-Toluene Sulfonic Acid Wastewater by Combined Photocatalysis and Ozonization

The degradation of low concentration of p-toluene sulphonic acid (p-TSA) in aqueous solution by three photochemical methods (O-3, TiO2/UV, TiO2/UV/O-3) were compared and the effects of initial pH, p-TSA concentration and ozone dosage on the p-TSA degradation by TiO2/UV/O-3 were studied. The results show that the degradation of p-TSA in three processes-O-3, TiO2/UV, TiO2/UV/O-3, follow the apparent first-order reaction kinetics. The rate constant of TiO2/UV/O-3 is larger than sum of those of TiO2/UV and O-3, which indicates a synergistic effect of photocatalysis and ozonization. The effect of pH on p-TSA degradation by TiO2/UV/O-3 can be ignored. The rate constant decreases with the increase of initial concentration of p-TSA, while the absolute removal amount of p-TSA increase of its initial concentration. The rate constant decreases with the increase of ozone dosage. Small organic molecules are identified as the main intermediate product during p-TSA degradation; and the ultimate products were H2O, CO2, indicating that TiO2/UV/O-3 is a safe and effective method to remove p-toluene sulphonic acid.