Research On The Hydrolysis And Photolysis Characteristics Of Bentazone

In this study,a rapid method for determination of bentazone in aqueous phase samples was developed,and the hydrolysis and photolysis characteristics of bentazone were studied.The rules of hydrolysis and photolysis of bentazone in different conditions were compared.The hydrolyzate and photoproducts were identified by UPLC-QTOF-MS,a preliminary explanation of the mechanism of photolysis and hydrolysis of bentazone.Also,the hydrolyzate and photoproduct,named 6-hydroxy bentazone,was detected by LC-MS/MS,and the condition of degradation of bentazone in aqueous phase was found.The results are helpful for further research of the migration and transformation process of bentazone in the environment.Moreover,it provides some basis for guiding the rational use of bentazone and the evaluation of the environment.The results are as follow.The hydrolysis of bentazone in different pH,temperature,surfactant,initial concentration,and concentration of metal ions were investgated.The results shown that bentazone was hydrolyzed under the pH value of 4,7 and 9,its half-life(T1/2)was 87 days,77 days and 58 days,respectively.It indicated that the hydrolysis rate of bentazone was accelerated with the increase of pH value.When the bentazone was hydrolyzed under the temperature of 15?,25?,35? and 45?,the T1/2 was 87 days,87 days,77 days and 69 days,respectively,It shown that high temperature could promote the hydrolysis,but low temperature was not conducive.The bentazone was hydrolyzed under the surfcatant of Twain 20,Twain 60,Twain 80 and sodium alkyl sulfonate(SDS),the T1/2 was 63 days,99 days,77 days,and 99 days,respectively.Compared with the control group(T1/2=77 days),Twain 20 was beneficial to the hydrolysis,and other surfactants were inhibited.Hydrolysis of betazone at initial concentration of 0.5 mg/L,1 mg/L and 1.5 mg/L,the T1/2 was 63 days,77 days and 87 days,respectively.It explained that the initial concentration of betazone may affects the hydrolysis,and the low initial concentration was beneficial to the hydrolysis,while the high initial concentration was unfavorable.When the bentazone was hydrolyzed under the concentration of Cu2+ of 1 mg/L,5 mg/L and 10 mg/L,the T1/2 was 53 days,50 days and 37 days,respectively.Compared with the control group,Cu2+ had a promoting effect on the hydrolysis,and accelerated with the increase of the concentration of Cu2+.Also,the bentazone was hydrolyzed under the concentration of Fe3+ of 1 mg/L,5 mg/L and 10 mg/L,and the T1/2 was 63 days,53 days and 46 days,respectively.Compared with the control group,Fe3+ had a promoting effect on the hydrolysis,and accelerated with the increase of the concentration of Fe3+.The photolysis of bentazone in different pH,surfactant,initial concentration,concentration of organic solvent and concentration of metal ions,under 500 w and 300 w high-voltage mercury lamp were studied.From the results we could conclude that bentazone was photolyed at the pH value of 4,7,and 9,its Ti 2 ranged from 2.3 h to 5.1 h.And it shown that alkalinity promoted the photolysis.The bentazone was photolyzed under the surfcatant of Twain 20,Twain 60,Twain 80 and SDS,the T1/2 ranged of 5.0 h-7.5 h,and different surfactant has light quenching effect on the photolysis.Photolysis of betazone at initial concentration of 0.5 mg/L,1 mg/L and 1.5 mg/L,the T1/2 ranged from 2.3 h to 5.8 h.The initial concentration was negatively correlated with the photolysis rate of bentazone.The photolysis of bentazone in the condition of methanol,acetonitrile,acetone and ethyl acetate,which concentration of 10%,20%and 30%.The T1/2 ranged of 3.2 h-12.2 h.Methanol and ethyl acetate had photocatalytic effect on the photolysis,while acetonitrile and acetone had quenching effect.When the bentazone was photolyzed under the concentration of Cu2+ and Fe3+of 1 mg/L,5 mg/L and 10 mg/L,its T1/2 ranged from 1.6 h to 4.4 h.Moreover,both Cu2+ and Fe3+ promoted the photolysis.In addition,the photolysis of bentazone under the conditions of 500 w high-voltage mercury lamp,300 w high-voltage mercury lamp and xenon lamp was also researched.The results showed that the photodissociation rate was the fastest and the slowest under the 500 w high-voltage mercury lamp and xenon lamp,respectively.The samples were identified by UPLC-QTOF-MS,the degradation products of bentazone in hydrolysis was mainly 6-hydroxy bentazone or 8-hydroxy bentazone.While the degradation products of bentazone in photolysis was mainly N-methyl bentazone and 6-hydroxy bentazone or 8-hydroxy bentazone.But for the degradation products are 6-hydroxy bentazone or 8-hydroxy bentazone,it needs to be further research.When the hydrolysis of bentazone in different conditions,which can detect 6-hydroxy bentazone.Its concentration gradually increased with the hydrolysis of bentazone,and increased to a certain concentration,slowly decreasing with the hydrolysis of bentazone,until it was lower than the limit of quantification(0.001 mg/L).And its concentration ranged from 0.001 mg/L to 0.009 mg/L.When the bentazone was photolyzed under different conditions,the photolysis production of 6-hydroxy bentazone was only found in methanol,ethyl acetate,and different surfactants.Also its concentration was increased first and then decreased,with ranged of 0.001 mg/L-0.008 mg/L.