Study On The Photosensitized Effect Of Gallic Acid Degradation On Chlorothalonil

The use of plant secondary metabolites to degrade environmental pollutants with photosensitization is of great significance to water pollution restoration.The bactericide chlorothalonil is highly toxic to aquatic organisms and the main degradation product in natural waters is the highly toxic 4-hydroxy chlorothalonil.This paper studies the effect of gallic acid on the photochemical degradation of chlorothalonil in different water bodies.Under ultraviolet light,high-pressure mercury lamp(HPML),and natural light(sunlight),the photochemical degradation of chlorothalonil is all affected by gallic acid.Promotional effect:The degradation products of chlorothalonil under the action of gallic acid were analyzed by high-resolution mass spectrometry,and the possible degradation mechanism was proposed.The research results are as follows:Under ultraviolet lamp,high pressure mercury lamp and sunlight,the degradation half-life of chlorothalonil in pure aqueous solution is T1/2 sunllght(693.15 min)>T1/2 uv(69.31 min)>T1/2HPML(46.21 min);The degradation reaction constant is Ksunlight(0.001 ?M min-1)<KUV(0.0l0 ?M min-1)<KHPML(0.015 ?M min-1).When the molar ratio of chlorothalonil(1 ?mol)to gallic acid is 1:1 and 1:10,under three different light sources(60 min):ultraviolet lamp,high-pressure mercury lamp,and sunlight,the effect of gallic acid on chlorothalonil The photodegradation of chlorothalonil has obvious promotion effect;the photosensitization rate of gallic acid to chlorothalonil is 10.0%,1240.0%;6.67%,666.67%and 300.0%,7100.0%;the degradation rate of chlorothalonil increases with the concentration of gallic acid And increase.The photodegradation products of chlorothalonil in pure water are mainly 4-hydroxychlorothalonil and dechlorination degradation products.When gallic acid is added,the inhibitory effect of gallic acid on 4-hydroxychlorothalonil produces a very small amount of 4-The main degradation products of hydroxychlorothalonil are 2,5-dichloro-1,3-phthalonitrile,2,4,5-trichloro-1,3-phthalonitrile,2,3,4,6-tetrachloro-5-cyanobenzamide,2,3,4,6-tetrachloro-5-cyanobenzoic acid.Under the action of gallic acid,the main degradation pathways of chlorothalonil in pure aqueous solution are reductive dechlorination and cyano hydrolysis.Under the high-pressure mercury lamp,when the molar concentration ratio of gallic acid to chlorothalonil is 5:1,the photodegradation rate constant of gallic acid increases from 0.013 ?M min-1 to 0.033 ?M min-1 which is a 2.5-fold increase;the half-life is from 53.32 min It is reduced to 21.00 min,which is 2.5 times shorter;when the light is 60 min,the molar concentration of gallic acid decreases by 6.69 mol/L.Gallic acid may participate in the photodegradation reaction of the metabolites of chlorothalonil and chlorothalonil.Under high pressure mercury lamp and sunlight,when the molar concentration ratio of gallic acid to chlorothalonil is 1:5,the photodegradation half-life of chlorothalonil in pond water,field water and paddy water is 10.83-13.33 min and 19.80-31.51 min,gallic acid also has a good promotion effect on the photodegradation of chlorothalonil in natural water.The photosensitization efficiency is lower than that in pure water.It may be because of the influence of humic acid and salt in natural water.The linear state of the bacteria list is excited to the triplet state.Gallic acid has obvious promotion effect on the photodegradation of chlorothalonil in different water bodies,and can inhibit the production of 4-hydroxy chlorothalonil,which has good theoretical significance and application value for the pollution restoration of chlorothalonil in water bodies.It has a certain guiding effect on the use of plant secondary metabolites to remove environmental pollutants.