Studies On Photochemical Degradation Of Chlorotoluron

The photochemical degradation of chlorotoluron irradiated by high pressure mercury lamp　(HPML) was investigated. The effects of types of water,　pH , pigments and surfactants on photodegradation of chlorotoluron in aqueous solution were observed. Photoproducts of chlorotoluron in aqueous solution under HPML were also identified. The main study results were summarized as follows:1.The photodegradation half-life of chlorotoluron in aqueous solution under HPML and sunlight was 14.72 min and 192.54 h. The photolysis rate of chlorotoluron under HPML was easily degraded under two light sources, and the photolysis kinetics of chlorotoluron in aqueous solution followed a first order reaction. The photolysis rate of chlorotoluron in five different types of water under HPML were found to increase by the order of doubly distilled water>tap water>lake water (Chaohu lake)>paddy water>river water.2.The photolysis half-life of chlorotoluron in buffer solutions of pH5,pH7,pH9 under HPML was 13.84min,15.37min and 16.31min respectively. The result showed that the photolysis half-life of chlorotoluron decreased with the increasing of solution pH.3.Four pigments could retard the photolysis rate of chlorotoluron in aqueous solution under HPML, the photosensitive efficiency was methyl blue -20.12%,methyl green -10.54%,congo red -26.24%,methyl orange -28.31% respectively.The photoquenching effects on photodegradation of chlorotoluron were increased with the concentration of different pigments increasing.4. Five surfactants could retard the photolysis rate of chlorotoluron in aqueous solution under HPML. The photosensitive efficiency was 　nongru-404 -10.54%,nongru-601 -27.96%,nongru 500 -25.24%,nongru 603 -21.05% and CTAB -11.22% respectively. The photoquenching effects on photodegradation of chlorotoluron were improved with the concentration of nongru-404,nongru-601 and CTAB increasing. While the photoquenching effects on photodegradation of chlorotoluron were weakened as the concentration of nongru-500 and nongru-603 increased.5.The photolysis kinetics of chlorotoluron including　a little acetone, methyl alcohol and acetonitrile in aqueous solution followed a first order reaction under HPML. 6.Several negative and positive ions could change the rate of photochemical degradation of chlorotoluron under HPML. The results: Mn2+ and Mg2+ could accelerate photochemical degradation of chlorotoluron in aqueous solution and had photosensitive effects on photochemical degradation of chlorotoluron in low concentration, the photosensitive efficiency was Mn2+ +4.10% and Mg2+ +4.49% respectively, but in high concentration acted as photoquenching effects on photochemical degradation of chlorotoluron; NO3- and NO2- had significantly photoquenching effects on photochemical degradation of chlorotoluron in aqueous solution , the photosensitive efficiency was NO3- -19.51% and NO2- -8.25% respectively, with concentration of them increasing, they took on photoquenching effects on photochemical degradation of chlorotoluron in aqueous solution much; Cl- and Br- could accelerate the rate of photochemical degradation of chlorotoluron in aqueous solution in low concentration under HPML, the photosensitive efficiency was Cl- +10.82%, Br- +3.90% respectively,and with concentration of Cl- increasing, the rate of photochemical degradation of chlorotoluron was decreased ,but as concentration of Br- increasing, the rate of photochemical degradation of chlorotoluron was increased,but I- could retarded the rate of photochemical degradation of chlorotoluron in aqueous solution under HPML, the photosensitive efficiency was -22.31% ,and as concentration of I- increasing, I- acted as photoquenching much.7.Photoproducts of chlorotoluron under HPML for a long time in aqueous solution were minerals such as Cl-,NO3-,NH4+,CO2.8.The middle photoproducts of chlorotoluron in aqueous solution were identified by GC-MS, obtained two photoproducts of chlorotoluron in aqueous solution under HPML, their molecular weights were 167 and 149, wi...