Studies On Photochemical Degradation Of Tebuconazole In Aqueous Solution

The photochemical degradation of tebuconazole irradiated by high pressure mercury lamp (HPML) was investigated. The effects of different light sources, pH, nitrate, nitrite, halogen ions, metal ions, pigments , surfactants, types of water and H2O2 on photodegradation of tebuconazole in aqueous solution were observed. The main study results were summarized as follows:1. The photolysis rate of tebuconazole under HPML was easily degraded and the photolysis kinetics of tebuconzole in aqueous solution followed a first order reaction. The photolytic half-life of tebuconzole was 29.0min in aqueous solution under HPML2. The photolytic half-lives of tebuconzole in buffer solutions of pH2.60,pH3.62,pH4.80,pH6.90,pH7.76,pH9.16,pH11.91 under HPML were 28.3min,27.8min,34.3min,25.3min,27.6min,26.0min,27.4min, respectively.3. Several negative and positive ions could change the rate of photochemical degradation of tebuconazole under HPML. The results: NO3- and NO2- had significantly photoquenching effects on photochemical degradation of tebuconazole in aqueous solution, With increasing of concentration, the photoquenching effects on photochemical degradation of tebuconazole in aqueous solution got stronger. The photochemical degradation of tebuconazole in aqueous solution was inhibited significantly by Cl-,Br- and I-, and the photoquenching effects of I- was followed by Br- and then by Cl-; NH4+ could accelerate photochemical degradation of tebuconazole in aqueous solution, and the photosensitive effects got stronger with increase of concentration.; Three metal ions showed photosensitive effects on photochemical degradation of tebuconazole in aqueous solution, the photosensitive efficiency were 35.18%, 18.24%, and 25.08% for Mn2+ Cu2+ Mg2+ respectively.4. Several pigments could change the rate of photochemical degradation of tebuconazole under HPML. The results: lactoflavin had significantly photoquenching effects on photochemical degradation of tebuconazole in aqueous solution, the max photoquenching efficiency in the experiment was 57.69%; Methyl green had not evident effects on photochemical degradation of tebuconazole in low concentration , but in high concentration methyl green had photoquenching efficiency and the photolysis half-life of tebuconzole was 46.5min; Methyl orange had photosensitive efficiency in low concentration on photochemical degradation of tebuconazole in aqueous solution and the photosensitive efficiency was 15.38%, but in high concentration it had photoquenching efficiency and the photoquenching efficiency was 66.54%; Crystal purple had photoquenching effects on photochemical degradation of tebuconazole in aqueous solution except in low concentratin, and the photoquenching efficiency in the experiment was up to 71.92%.5. Six kinds of surfactants could retard the photolysis rate of tebuconazole in aqueous solution under HPML exclude nongru-BY-140. The photolysis half-life of tebuconzole in the experiments were 61.9min,68.0min,70.0min,57.8min,56.4min respectively. Nongru-BY-140 had lest effects than others on photochemical degradation of tebuconazole in aqueous solution, and The photolysis half-life of tebuconzole in the experiments were 25.3min,33.3min,25.8min respectively.6. The photolysis rate of tebuconazole in four different types of water under HPML were found to increase by the order of distilled water>tap water>lake water (Chaohu lake)>pond water. The photolysis kinetics of tebuconazole in aqueous solution followed a first order reaction. The photolysis half-life of tebuconzole in the experiments were 28.5min,31.2min,36.8min,39.2min in distilled water,tap water,lake water and pond water, respectively.7. H2O2 could accelerate the photolysis rate of tebuconazole in aqueous solution under HPML. It's photosensitive efficiency in the experiment was up to 50.90%.