| Disinfection by-products(DBPs)are formed during the disinfection of tap water,but many DBPs are not found,so total organic halogen(TOX)is proposed to represent the total amount of these mixed disinfection by-products.The separation step in the conventional TOX detection method has many problems,so this topic proposes to use electrodialysis(ED)pretreatment to separate the soluble organic halogen and the inorganic halogen.However,in the process of processing the actual water sample,it shows that the deionization effect and the organic substance retention effect of the device were not satisfactory,and the device stability was poor.In order to solve the above problems,the subject improved the experimental device,optimized the experimental conditions,and analyzed the organic halogen loss path.Finally,the organic halogen formation of the actual water sample was studied.The conclusions are as follows:The electrodialysis reactor was designed and the experimental conditions were explored.Under the experimental conditions,the stability of the device operation was verified by using the spiked sample of tap water.During the seventeen hours of continuous operation,the removal rate of chloride ions was more than 99%,and the retention rates of organic halogens and total organic carbon were also good.When the water sample is more complicated and the inorganic ion content is higher,the flow rate or voltage needs to be changed to increase the removal rate of the halogen ion.Therefore,it is necessary to examine the removal rate of halogen ions and the retention rate of organic halogen in different voltages and different flow rates.When the voltage is increased or the flow rate is lowered,the removal rate of the halogen ions is increased,and the retention rate of the organic halogen is lowered,but the flow rate has a greater influence on the retention rate of the organic halogen.And for lake water,river water and the sewage,the spiked recovery test has been carried out,which has better effect.In order to explore whether the retention rate of these organic halogens can be further improved,the cause of the loss of organic halogens is further analyzed.The organic halogen loss path is divided into four aspects: pipeline adsorption,membrane adsorption,diffusion and electromigration.The experiment found that there are obvious pipeline adsorption and membrane adsorption phenomena for the halogenated methane species,and the adsorption loss rate is about 20%.For the halogenated acetaldehydes,there is obvious electromigration,and the loss rate is probably Between 10% and 20%;for halogenated acetonitriles,but the electromigration is more obvious.The TOX was generated by adding residual chlorine to the actual water sample to investigate the treatment effect of the electrodialysis process on complex actual water samples.The results of the four groups of experiments show that the organic matter with a relative molecular mass of less than 1000 accounts for the majority of the total,and these small molecular substances mainly react with the residual chlorine to form disinfection by-products.As the amount of residual chlorine added increases,the production of disinfection by-products also increases.When bromide ions are added to the water sample,the total amount of organic halogen produced increases.After the four water samples were electrodialyzed,the TOX was detected.The removal rate of chloride ions in the electrodialysis process was over 99%,and the retention rates of several typical organic halogens and total organic carbon were higher.The amount of TOX produced is positively correlated with the amount of several disinfection byproducts detected.In summary,the experimental equipment and experimental conditions were optimized,and the causes of organic halogen loss were analyzed.On this basis,the organic halogen formation and treatment of the actual water sample was carried out,which laid the foundation for the practical application of the subsequent organic halogen. |
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