Study On The Photosensitization Of Single Phenolic Substances On Chlorothalonil In Aqueous Solution

Chlorothalonil is a highly effective and low-toxicity broad-spectrum fungicide,it was mainly used for the prevention and control of rust,anthracnose,powdery mildew,downy mildew on fruits and vegetables and fruit storage.Chlorothalonil is widely used in the world,and it had been detected in the atmosphere,soil and water environment due to its stable nature.The main metabolites of Chlorothalonil in the environment are4-hydroxy-chlorothalonil,which was 30 times more toxic than Chlorothalonil.In order to degrade quickly and efficiently and change the metabolic pathways of chlorothalonil,we selected single phenolics such as salicylic acid and phenol to study the photosensitization.1.Salicylic acid and Phenol had obvious promoting effect on the photolysis of Chlorothalonil,and with the increase of concentration,the photolysis rate of Chlorothalonil increased gradually.For photolysis liquid of 0.5mg/L Chlorothalonil,the photolysis rate was 0.019?mol/L,and the half-life of the photolysis was 36.47min.For photolysis liquid of Chlorothalonil:SA=1:0.5?1:1?1:2?1:3?1:5,which the photolysis rate was 0.062?0.115?0.205?0.283?0.441?mol/min,and the half-life of the photolysis was 16.18?6.03?3.18?2.45?1.57min.For photolysis liquid of Chlorothalonil:Phenol=1:0.5?1:1?1:2?1:3?1:5,which the photolysis rate was 0.056?0.104?0.118?0.305?0.415?mol/min,and the half-life of the photolysis was 12.38?6.66?3.69?2.27?1.67min?2.SA and Phenol had obvious inhibitory effect on increase drug metabolism of Chlorothalonil,when concentration of SA and Phenol was higher,the conversion rate of4-hydroxy chlorothalonil was lower,and add the material for 4-hydroxy chlorothalonil photosensitization effect.And SA and Phenol had no photosensitize effect on 4-hydroxyl chlorothalonil.When molar concentration of CHT:SA=1:0.5,1:1,1:2,1:3,1:5,the conversion rate of paeonium to 4-hydroxy chlorothalonil was 6.7%,5.6%,4.8%,4.2%,and 4.5%;when CHT:phenol=1:0.5,1:1,1:2,1:3,1:5,with conversion rates of 11.8%,10.9%,9.8%,9.2%,and 7.9%.3.The photosensitization efficiency of SA and Phenol for Chlorothalonil under High Pressure Mercury Lamp was higher than that of the Sunlingt.When we added phenol,the degradation rate under HPML is 4.95 times of the Sunlight.When we added SA,the degradation rate under HPML is 4.88 times of the Sunlight.4.SA and Phenol had the same photosensitization effect on Chlorothalonil,which was mainly manifested in the reduction of Cl.we mainly detected two products:2,4,5-dichloro-l,3-dicyanobenzene and 2,5-dichloro-l,3-dicyanobenzene.Two metabolites are primary metabolites of Chlorothalonil.2,4,5-dichloro-l,3-dicyanobenzene was further degraded.2,5-dichloro-l,3-dicyanobenzene photolysisded slowly,and at 60min,The sum of the Cl~-of 2,5-dichloro-l,3-dicyanobenzene and the Cl~-in the photolytic solution was4.07 times the initial concentration of Chlorothalonil.That means under the action of the added substance,in addition to a small amount of 2,5-dichloro-1.3 phenylenitrile in the photolytic solution,all other products are completely dechlorinated.