||Many organic compounds have been synthesized, manufactured and produced as the chemical industry booming. With the growing demand for polyester fiber, the raw material, terephthalic acid manufacturing process produced large quantity of wastewater containing organic pollutants. In this study, UV/hydrogen peroxide was applied to treat the two main organic pollutants, benzoic acid and p-toluic acid in the terephthalic acid manufacturing process wastewater. The effects of treatment and the parameters of reaction kinetics were analyzed and discussed under varying reaction conditions.
The experimental results showed that initial hydrogen peroxide to the acid molar ratio ranging 1 to 4 gives the best treatment effect with the apparent kinetic constants (kobs) 252min-1 and 517 min-1 for benzoic acid and p-toluic acid, respectively. Furthermore, benzoic acid was more easily affected by the hydrogen peroxide dosage compared to p-toluic acid. The results also showed that the apparent kinetic constants decreased with increasing initial concentration of the organic acids. With lower initial acid concentrations, the reactions followed pseudo first order kinetics, but the reactions approached zeroth order when the initial concentration was as high as 300ppm. In the experiments, the reactions of the two compounds behaved differently at different reaction temperatures. For example, the degradation rates of benzoic acid was poor at 35 ℃, but was the highest for p-toluic acid at the same temperature. It was found that the solution pH of 7 was the optimal pH for benzoic acid or p-toluic acid degradation. From the series of experiments under the same reaction conditions, p-toluic acid was found to be easier to decompose than benzoic acid. All results showed that all the degradation rates after two hours were greater than 80% when the initial concentration was 50 ppm. All the experimental results showed that the experimental data were correlated well with a pseudo first-order kinetic model. Therefore, it was concluded that the pseudo first-order reaction kinetic model could be applied to predict the degradation conversions for given operating conditions.