Photosensitive Degradation Of Chlorothalonil And Its Isomers By Four Catechins

Chlorothalonil(m-tetrachlorophthalonitrile)has two isomers: o-tetrachlorophthalonitrile and p-tetrachlorophthalonitrile.There are widely used in agricultural medicine,medicine,fuel and other fields.Due to the development of pesticide and chemical industry,chlorothalonil and its isomers are frequently detected in water.Photochemical degradation is one of the important ways for the decomposition and transformation of exogenous compounds in the environment.Although people have done a lot of research on the mechanism and influencing factors of photochemical degradation.However,the photodegradation of chlorothalonil and its isomers in natural water is still less studied.Therefore,it is of great significance to study the photochemical degradation and environmental effects of chlorothalonil and its isomers in natural water.An HPLC method for the determination of chlorothalonil tetrachloro phthalonitrile and tetrachloro-p-phthalonitrile was established;Catechin(c),epicatechin(EC),epigallocatechin(EGC)and epicatechin gallate were studied(ECG)the photodegradation of chlorothalonil by four different catechins under sunlight,UV and mercury lamp conditions;the degradation products of chlorothalonil were analyzed qualitatively and quantitatively by high performance liquid chromatography,and the effects of different catechins on chlorothalonil and its isomers in pure water,gutter water,pond water and paddy water and under different light sources were explored Degradation effect.The main results are summarized as follows:1.Under the irradiation of mercury lamp,ultraviolet lamp and sunlight,the photodegradation rates of catechin,epicatechin,epigallocatechin and epicatechin gallate on chlorothalonil in aqueous solution increased by 2.24-37.1 times,0.80-34.7 times and0.33-21.3 times respectively.Under the same molar concentration ratio,the enhancement of four catechins under different light sources is high pressure mercury lamp > ultraviolet lamp > sunlight.The photodegradation of chlorothalonil by catechins under different light sources accorded with the characteristic equation of first-order degradation kinetics.2.The photodegradation rates of catechin,epicatechin,epigallocatechin and epicatechin gallate to chlorothalonil isomer tetrachlorophthalonitrile under high pressure mercury lamp increased by 1.33-3.33 times,and their photodegradation accorded with the first-order degradation kinetic characteristic equation.Chlorobenzonitrile,an isomer of chlorothalonil,does not undergo photodegradation under the action of four catechins.3.The determination results of hydroxyl radical showed that the addition of catechins inhibited the production of hydroxyl radical,and the photocatalytic degradation pathway of chlorothalonil was mainly photocatalytic reduction dechlorination;Under the conditions of solar light source,ultraviolet light and mercury lamp,the degradation products of chlorothalonil are 2,4,5-trichloro-1,3-dicyanobenzene,2,5-dichloro-1,3-dicyanobenzene and 5-trichloro-1,3-dicyanobenzene,avoiding the formation of highly toxic hydroxylation products.4.Catechin,epicatechin,epigallocatechin and epicatechin gallate have different photodegradation promoting effects on the photodegradation of chlorothalonil and its isomers,and there is a certain structure-activity relationship between structure and activity.5.In different water bodies,the promoting effects of catechin,epicatechin,epigallocatechin and epicatechin gallate on the photodegradation of chlorothalonil were pure water > pond water > gutter water > paddy field water.