Analysis Of Trichloronaphthalene On The Surface Of Kaolin And Study On The Photoconversion Process

Polychlorinated naphthalenes are abbreviated as polychlorinated naphthalenes(PCNs),which refers to a type of persistent organic pollutants(POPs)generated by the chlorination of molten naphthalene.POPs have long-term residual,bioaccumulative,semi-volatile,and highly toxic.They can migrate over long distances around the world and have serious hazards to human health and the global environment.Polychlorinated naphthalenes are therefore becoming a major research focus in the field of environmental science.At present,the polychlorinated naphthalene homologous group that dominates in various environmental matrices is the trichloronaphthalene(tri-CN)homologous group.Therefore,in this experiment,the 2,3,6-trichloronaphthalene(CN-26)in the trichloronaphthalene homologous group Naphthalene was studied as a target pollutant.First,the Gas-chromatography analysis method of CN-26 and the ultrasonic extraction method on the surface of kaolin were optimized,and then the UV lamp(λmax=365nm)was used as the light source to carry out the study of the phototransformation of CN-26 on the surface of kaolin,through kinetic analysis and single factor The experiment obtained the phototransformation mode of CN-26 on the surface of clay mineral kaolin and the influence of various influencing factors and complexes on the phototransformation of CN-26.Finally,gas-phase mass spectrometry was used to analyze the product and infer the degradation pathway of CN-26.The main conclusions are as follows:(1)CN-26 on the surface of kaolin can be extracted into n-hexane by ultrasonic extraction experiment.Under the conditions of extraction time 20min,extraction frequency 40KHz,extraction temperature 20℃,and extractant(n-hexane)volume of 15mL,CN-The extraction rate of 26 is 97%～103%.(2)According to the data fitting of the photochemical conversion results of CN-26 on the surface of kaolin,it is found that the photochemical conversion process conforms to the LH model,indicating that there is both direct photolysis of CN-2 6 in the kaolin system and indirect light on the surface of the soil layer.solution.(3)The experimental conditions for the photochemical conversion of CN-26 on the surface of kaolin:use the ultraviolet light with a power of 30W,an irradiance of 0.15W m-2,and a wavelength of 365 nm as the light source,when the initial concentration of CN-26 in the kaolin is 6μg After g-1,7 days,the conversion rate of trichloronaphthalene in the light reaction group was 84%,and that of the dark reaction group was only 17.8%.(4)The complex citric acid has an inhibitory effect on the phototransformation of CN-26,and sodium sulfite has no effect on the phototransformation of CN-26.(5)The photoconversion pathway of CN-26 includes two stages of dechlorination and ring opening.The products include ethylbenzene,p-xylene,cyclopropylbenzene,etc.The conclusion of this experiment can supplement the gas chromatography quantitative analysis method of trichloronaphthalene homologous group,and can also conduct a certain degree of basic exploration for the photochemical conversion process of trichloronaphthalene on the surface of kaolin.