Visible light-induced photodegradation of simazine in aqueous TiO 2 suspension

The degradation of simazine (SMZ) in TiO2 suspension with the presence of H2O2 was investigated under the irradiation of 420 nm lamps. This process could be optimized by adjusting TiO2 dosage, initial concentration of H2O2, and the initial pH of the solution. The optimum TiO2 dosage was found to be 0.1 g/L, and the highest SMZ decay rate was achieved with the initial H2O 2 concentration at 4 mM. Overdose of H2O2 is found to be more critical in jeopardizing the SMZ decay than the overdose of TiO2. A neutral initial pH level at 6.5 was found to be favorable for SMZ degradation. The presence of Cr(VI) significantly accelerated SMZ degradation in the TiO2/H2O2/vis (visible light) process. In addition, 10 simazine derivatives were identifed by liquid chromatography-mass spectrometry/mass spectrometry. It was suggested that dealkylation is the major pathway of SMZ photodecay in the TiO 2/H2O2/vis process. The final product was found to be ammeline.