Photocatalytic oxidation of propoxur in aqueous titanium dioxide suspensions

The photocatalytic oxidation of propoxur, a nitrogen-containing pesticide, has been investigated using aqueous TiO2 suspensions as catalyst in this st udy. The operating variables considered in the study were initial pH, tempe rature, [H2O2] and TiO2 loading. Results showed that 1 g/l of TiO2 was the optimum dosage for oxidizing propoxur in this system. Hydrogen peroxide can increase the oxidation rate with increasing its initial concentration. The re was no obvious difference in the rate of propoxur oxidation at the initi al pH of 4, 6 and 9, and the final pHs of reaction solutions were around 5. 5. However, propoxur degraded slower at initial pH 2, and the pH did not va ry during the period of photocatalytic reaction. The photocatalytic oxidati on of propoxur using TiO2 suspensions as the photocatalyst was reaction-con trolled as indicated by the activation energy.