Studies On Photochemical Degradation Of Fenarimol In Sorption

The photodegradation of fungicide Fenarimol by high pressure mercury lamp(HPML) has been studied on surface of silica gel chromatoplates and in soil. With HPTLC,FT-IR and GC-MS as analytical techniques, we also explored the photoproducts of Fenarimol in acetonitrile and soil under HPML. The main study results were summarized as follows:1. The photolytic rate of Fenarimol on surface of silica gel under HPML is quick. The half life is only 6.49 minutes.2. With silica gel as soil condition ,we studied the photodegradation rules of Fenarimol. The dose of spot should be during 500-800ng. Under HPML the photolytic rate of fungicide Fenarimol decreased with the increasing of dose.3. Organic pigments showed remarkable photo-quenching effects on the photolysis of Fenarimol on the surface of silica gel chromatoplate. Dealing with five kinds of pigments, the half life of photolysis is extended to 5.59, 3.12, 1.83, 1.12 and 9.37 times respectively. After ten minutes the photo-quenching effects rates of pigments were 5.58-83.26%. The order of photo-quenching effects rates is methylene blue>crystal purple>malachite green>lactoflavin>methylic orange.4. The loading rate of pigments have great effect on the photo-quenching effects. The photo-quenching effects of crystalpurple and methyleneblue increased with the dose. When the loading rate of crystalpurple mixed with Fenarimol in 1:0.1,1:1 and 1:4 under HPML ten minutes later the photolysis rate decreased from 30.6% to 19.3 and 6.4% in turn. When the dose rate of methyleneblue mixed with Fenarimol in 1:0.1,1:1 and 1:4 under HPML ten minutes later the photolysis rate decreased from 30.6% to 19.3 and 6.4% in turn.5. In dry soil the photodegradation of Fenarimol was very slow. The photodegradation can not be observed after 100 hours irradiation. In wet soil the half life of Fenarimol is 2.7 hours. It is showed that water is the key to photolysis of Fenarimol.6. With the HPML as light source, the degradation of Fenarimol followed a first-order kinetic in soil with different pH. The photolysis rate of Fenarimol is pH4> pH9> pH7. The half life is 1.09,1.61 and 2.70h respectively. It showed whatever acidity or alkalescence condition can accelerate the degradation rate.7. In all kinds of conditions photo-abruption and photo-oxygenation are the main approach of photodegradation. DCBP and chlorobenzeneacid are the main production of this reaction. There are two active sites of Fenarimol molecule. One is C-C bond between pyrimidine andɑ-C atom; the other is hydroxide group ofɑ-C atom. In this reaction the C-C bond is easy to be broken and lead to pyrimidine group fallen off. The production of above reaction is 2,4-dichlorobenzenemethanol. After the pyrimidine fell off the C-atom in main chain is not saturation and easily to be oxygenated. DCBP is produced. If one of chlorobenzene groups has fallen off the C-atom will be further oxygenated and production is chlorobenzene carboxylic acid.