Photochemical Degradation Of Bisphenol A(BPA) In Water Under Vacuum Ultraviolet Light

Bisphenol A(Bisphenol A,BPA)is a typical environmental endocrine disruptor in water.Because of its stable chemical structure and diffcult biodegradation,it can be kept in the environment for a long time,especially in the water.At present,the conventional water treatment process can't completely remove it and produces more toxic by-products.Therefore,it is very important to study the safe and effective BPA degradation pathway.In this paper,the photodegradation and photocatalytic degradation of BPA under 185nm vacuum ultraviolet irradiation were studied.By investigating the effects of various factors,the degradation products were analyzed and identified,and the possible degradation mechanism of BPA was deduced.The following results were obtained:(1)The photodegradation of BPA:?The degradation efficiency of BPA under 185nm vacuum ultraviolet light in Air,N2 and O2 were much higher than 254nm ultraviolet light,and the degradation efficiency of BPA was Air>O2>N2.The TOC reduction rate was O2>Air>N2,and the toxicity of BPA solution in Air atmosphere almost completely disappeared after 60 minutes.?The degradation rate of BPA with an initial concentration range of 5 to 100 mg·L-1 decreased with the increased of initial concentration,but all followed pseudo-first-order reaction kinetics.?When the initial pH of the solution was 5.94,the effect of BPA degradation was best,and the molecular BPA was more easily degraded than the phenol anion BPA.?Through the free radical trapping inhibition experiment,it was found that the photodegradation of BPA mainly depended on direct photolysis,and 02-· and 1O2 played a major role in the oxidation of active substances.?The reaction rate constant of BPA coexisting with common anions in water was k(co2-3)<k(NO-3)<k(HCO-3)<K(Cl-)<K(SO2-4)·?Degradation efficiency of BPA in different water matrix was following order:ultrapure water>tap water>river water.BPA degradation in ultrapure water was better than tap water and river water as a result of solution pH,DOM and anion,and DOM was the main reason for the difference of tap water and river water.?The intermediate products of photodegradation of BPA were p-Benzoquinone,Phenol Hydroquinone,and 2-Ethyl hexanol.After oxidation and ring opening,the intermediate products were finally mineralized into CO2 and H2O.(2)The photocatalytic degradation of BPA:?The TiO2 thin film catalyst preparing by the sol-gel method was mainly anatase structure,and had a certain photocatalytic activity and reaction stability.?The photocatalytic degradation of BPA with an initial concentration of 5?100 mg L-1 followed the pseudo-first-order reaction kinetics,and the reaction rate constant decreased with the increased of its initial concentration.?Through radical scavenger inhibition experiments,it was found that HO· promoted photocatalytic degradation of BPA to some extent.?Alkaline solution was not conducive to the photocatalytic degradation of BPA.?The study of the effect of common anions in water showed that Cl-,NO3-,and CO32-had different degrees of inhibition on the photocatalytic degradation of BPA,and the size was followed by NO3->CO32->C1-.However,SO42-had almost no effect.?The intermediate products of BPA photocatalytic degradation included Dodecane,4-Isopropylphenol,n-Tetradecane,2,5-Dimethylbe-nzoicacid,2'-Hydroxyacetophenone,4'-Cyclohexylacetophenone,Hydroquinone,p-Benzoquinone and Phenol.After oxidation and ring opening,the intermediate products were finally mineralized into CO2 and H2O.