Inhibitory Effect Of Catechins On The Photodegradation Of Profenofos In Water

Profenofos（PFF）is widely used as an insecticide against various pests in cotton, vegetables and other crops.Catechins are natural plant flavonoids with strong antioxidant properties.The objective of this study is to investigate the photodegradation of profenofos in water and the effect of catechins on this process.The photodegradation of profenofos in different types of water,the effects of catechin concentrations and ions(SO₄^2-,NO₃^-)on profenofos degradation under high-pressure mercury lamps,xenon lamps,UV lamps and sunlight were studied.Try to eliminate the inhibitory effect of catechins by activating sodium persulfate;ESR spin capture technology was used to elucidate the active oxidized species in the phosphorescence degradation of propyl bromide.The change of bromine ion content during phosphorescence degradation of propyl bromide was quantified by ion chromatography.The phosphorescence degradation products of propyl bromide were identified,and further degradation studies were carried out on the products.The main findings are as follows:1.Under the irradiation of high-pressure mercury lamp,xenon lamp,ultraviolet lamp and sunlight,the degradation half-life of profenofos in ultrapure water is 0.125 h,4.55 h,7.01 h and 88.52 h respectively;when the molar ratio is 1:1,1:5,1:10 and 1:20 of catechin,the half-life of probromide phosphorescence degradation under four light sources were 0.134～0.204h,8.22～13.52 h,7.18～7.73 h,132.03～222.88 h,indicating that catechin can inhibit the degradation of probromide in aqueous solution,and the greater the inhibitory effect of catechin added dose.2.Under the high-pressure mercury light,compared with ultrapure water,the half-life of profenofos in three kinds of natural waters has been prolonged,and the specific performance is T1/2 ultrapure water（8.86 min）<T1/2 pond water（14.43min）<T1/2 field ditch water（16.12min）<T1/2_{paddy field water}（17.42 min）,the degradation rate of profenofos is affected by the chemical substances in the water body,and the degradation rate of profenofos in pure water is the fastest quick.After adding catechin at a molar ratio of 1:20,the half-lives of profenofos were9.47 min,18.41 min,19.05 min,and 19.10 min,respectively,all of which were extended to a certain extent.The complex soluble and insoluble substances in natural water may cause the difference in the photolysis rate of profenofos.The research results showed that adding SO₄^2-and NO₃^-alone can inhibit the photolysis of profenofos to a certain extent.3.Under the irradiation of a high-pressure mercury lamp,added isopropanol,sodium azide,and sorbic acid to the aqueous solution of profenofos,and compared with the photodegradation of profenofos itself,it was found that R_3PFF*is 72.78 during the photolysis of profenofos%,R_1O2 is 4.02%,and R·OH is 8.43%.It can be speculated that the photolysis mechanism of profenofos is（1）after light absorption,profenofos is transformed into active PFF*,and then directly photolyzed;（2）PFF*the energy is transferred to the dissolved oxygen in the solution to generate active oxygen ROS,which oxidizes and degrades profenofos.4.Under the irradiation of high-pressure mercury lamp,the addition of sodium persulfate can promote the degradation rate of profenofos,and the effect increased with the increase of the concentration.However,after adding excessive catechin,its promoting effect disappeared and showed a weak inhibitory effect.It was speculated that the sulfate radical produced by the activated sodium persulfate first reacted with the more reductive catechin,and then Sulfate ions with an inhibitory effect were produced to compete for the energy of photons and prolong the half-life of profenofos.5.Under the high-pressure mercury lamp light,the content of bromide ions decreased significantly after profenofos aqueous solution was added with catechin.The PNDA trapping hydroxyl radical test showed that hydroxyl radicals were generated during the photoprobe bromide degradation process,and the content of hydroxyl radicals decreased sharply after adding catechin.ESR detection showed that hydroxyl radicals,alkoxyl radicals and singlet oxygen were produced during the degradation process of profenofos aqueous solution under light,but the above radicals did not occur in profenofos aqueous solution after adding catechin.High performance liquid chromatography detection result showed,the product in the phosphorescence degradation process of propyl bromide has O-（2-phenyl）-O-ethyl-S-propyl phosphorothioate and 4-bromo-2-chlorophenol.Catechin did not change the original photodegradation pathway of profenofos,catechin could inhibit O-（2-phenyl）-O-ethyl-S-propyl phosphorothioate and 4-bromo-2-The photodegradation of chlorophenol,and stronger photodegradation inhibitory effect on 4-Bromo-2-chlorophenol than on profenofos.