The Study On The Degradation Of Clothianidin By Dielectric Barrier Discharge Non-thermal Plasma

China is an agricultural country,annual amount of production and use of pesticide in China has been the forefront of the world since the beginning of the twentieth century.In recent years,with the wide use of pesticides and development of new pesticides,environmental pollution incidents,pesticide residues and food safety problems caused by pesticide gradually became the attention of people.Pesticides could destroy pests to protect crops,and it has strong diffusion ability,permeation,concentration,polymerization and other behavior of pesticides in natural environment,which causes a harm to water,atmosphere,soil and biological,therefore it is imperative to control pesticide pollution.Clothianidin is a new kind of neonicotinoid pesticides and one of the most widely used pesticides,which are persistent,mobility and light absorbing in the environment,and it could penetrate into groundwater quickly.Traditional treatment of pesticide wastewater cannot completely applicable to the degradation of new pesticide,thus it is necessary to put forward a new kind of efficient technology to the degradation of pesticide wastewater.Dielectric barrier discharge plasma technology(DBD)is one of the advanced oxidation technology,which has the function of high energy electron radiation,ultraviolet decomposition,oxidation of ozone and reactive radical particles,it has wide application in wastewater treatment.Thus the article selected dielectric barrier discharge plasma technology combined with the catalyst of titanium dioxide-graphene to degrade the target pollutants-clothianidin.In this paper,we prepared titanium dioxide-graphene catalysts with different proportion(Owt%,1wt%,2wt%,5wt%,8wt%,10wt%)to the honeycomb ceramic plate by sol-gel method,and modified catalysts were characterized by XRD,SEM,FTIR and DRS experiments.According to results of the characterization experiment and the degradation efficiency of clothianidin with different proportion of the catalysts,8wt%Gr-TiO2 was chosen as the best proportion of catalytic ceramic plate.To explore the degradation effect of clothianidin with different condition by dielectric barrier discharge technology,the paper studied the initial concentration of pollutants,the solution of initial pH,conductivity,input power,metal ion and inhibitor in TiO2-8%Gr-DBD,respectively.Through experimental analysis,too high concentration of clothianidin is adverse to the degradation efficiency,when the concentration is too low,the energy yield of the system will be low,so the best efficiency was obtained when the initial concentration is 100 mg/L;High or low input power of the system are detrimental to the degradation of clothianidin,when the input power is too low,it will make weaker high-energy-electron radiation and UV light intensity,while the input power is too high,the discharge will appear unstable,so the best input power of 200 W;In the degradation process of clothianidin under acidic condition,hydrogen peroxide generated to hydroxyl free radicals by photolysis,it could enhance the oxidation ability of the system,while in the neutral and alkaline conditions,hydrogen peroxide could react with hydroxyl radicals,and consumed the part of hydroxyl radicals,it is unfavorable to the degradation of clothianidin;When the initial solution conductivity is 150 ?S/cm,the degradation efficiency of clothianidin is the highest,and when the initial conductivity increased to 300 ?S/cm and 450 ?S/cm,too much salt in the solution molecules will hinder the high-energy electron transfer in the catalyst,it consumed part of the active particles and reduced the degradation effect;The Fe2+ and Cu2+ could improve the efficiency of the degradation of clothianidin and clothianidin was completely degraded within the degradation time;The degradation efficiency decreased with the increasing of concentration of isopropyl alcohol.At the same time,the experiment proved that the solution pH reduced and conductivity increased in the degradation process.Finally,the paper qualitatively analyze intermediate and final product,degradation mechanism and degradation paths of clothianidin by high performance liquid chromatography-mass spectrometry,it can provide theoretical guidance in pesticide wastewater treatment by plasma processing technology.