Study On The Transformation Characteristics Of Sodium Diatrizoate In Drinking Water Disinfection Process

Iodinated X-ray contrast media is widely used in soft tissue imaging?such as organs,veins,blood vessels?,CT and MRI enhanced detection.At present,the consumption has reached 3.5×10³ tons per year in the world.Due to these substances has very stable chemical structure,highly hydrophilic,it is often difficult to be absorbed,oxidized and biodegraded.Thus,its widely exist in effluent of sewage treatment plant,surface water and groundwater.China is one of the countries with the largest consumption of ICM in the world.ICM pollution is also serious in domestic water bodies.Such as the detected concentration of iopamidol was 0.26-0.68?g/L in Huangpu River.In the context of continuous renovation of water treatment process,to reduce the risk of drinking water.It is great significance to find a cost-effective removal method for ICM.The dissertation takes typical ionic ICM sodium diatrizoate as the research object.The degradation rules under five kinds of drinking water disinfection technology including chlorination,chlorination,ozonation,UV and UV/chlorine were discussed,and then established its kinetic model.The results show:Sodium diatrizoate does not degrade under the chlorination and chloramination,under the conditions of ozonation sodium diatrizoate degradation,the degradation rate reached 91.0%when the reaction to 60 minutes,and the degradation met the pseudo first-order reaction kinetic model,the rate was0.04687 min^-1.The pH of the solution has a greater impact on the degradation of sodium diatrizoate.Under alkaline conditions,the rate of ozone degradation of sodium diatrizoate was significantly higher than that of acidic conditions.When bromide existed in the solution,it can be seen that the degradation of sodium diatrizoate has been inhibited.This is due to the formation of bromate,hindered the degradation of sodium diatrizoate.When adding HCO₃^-,CO₃^2-and tert-butanol alcohol as hydroxyl radical inhibitors.The degradation of sodium diatrizoate was also significantly inhibited due to hydroxyl radicals play an important role in the ozonation of sodium diatrizoate.During UV photolysis sodium diatrizoate,when the reaction proceeded to10 min,the removal rate was 86.8%.UV degradation of sodium diatrizolate met the pseudo first-order reaction kinetic model,the rate was 0.2022 min^-1.The different pH values and the presence or absence of bromide in the solution have essentially no effect on UV photodissociation of sodium diatrizoate.In the process of UV/chlorine treats sodium diatrizolate,when the reaction proceeded to 1.5 min,the removal rate was 92%.The degradation of sodium diatrizolate met the pseudo first-order reaction kinetic model,the rate k_obs was0.02807 min^-1.The degradation of sodium diatrizoate was influented by the reaction of hydroxyl radical oxidation and UV photolysis.With the increase of chlorination,the degradation rate of sodium diatrizoate increased.The pH in solution has a large effect on the degradation of sodium diatrizoate.The rate of degradation under alkaline conditions is higher than that under acidic conditions.When bromide existed in the solution,the rate of degradation of sodium diatrizoate decreases with increasing bromine content.Sodium diatrizoate can be degraded by ozonation,UV and UV/chlorine combined process,respectively.A series of disinfection by-products are generated during subsequent chlorination.Among them,the types and amounts of disinfection by-products generated by ozonation are the least,and only a conventional halogenated disinfection by-product of trichloromethane is detected.Seven kinds of disinfection by-products were detected under UV and UV/chlorine combined processes.Among them,three iodinated disinfection by-products were dichloro-methyl iodide,monochloroiodomethane and triiodomethane.Four conventional halogenated disinfection by-products:chloroform,dichloroacetonitrile,trichloronitromethane,trichloroacetone.However,the amount of production and the main types of disinfection byproducts are different.When there is bromide ion in the solution,the types and amounts of disinfection byproducts produced by the above three kinds of disinfection processes have great changes.