Study On Mechanism And Regulation Of Stepwise Desalination By Combination Of Ion Exchange And Electrodeionization

With the rapid development of semiconductor industry in recent years,the demand for pure water has increased greatly.Reverse osmosis process is mostly used in seawater desalination in China,and some ions still exist in the secondary reverse osmosis water.If it is not removed,it is directly used as water for production in the electronics industry,which will lead to lower product quality.In recent years,the preparation technology of pure water in our country has been widely concerned.Mixed bed and electric deionization process are often used to prepare pure water.Mixed bed operation often presents problems such as short flow,poor water quality,incomplete resin regeneration,etc.Electric deionization process often presents problems such as unstable water quality and high energy consumption.This article adopts the ion exchange and electric ion technology,ion exchange and electric combination to ion process continuous desalting system,using common commercialization of anion exchange resin to remove residual ion secondary reverse osmosis,the water,at the same time in the further for desalination of water,acid and alkali regeneration of ion exchange process of the mixed bed process was optimized,and achieve the purpose of reducing the generation of waste liquid;The current efficiency in the process of electrodeionization is calculated to reduce the energy consumption in the process of desalination.The results of static adsorption experiments show that there are significant differences between different types of ion exchange resins in the adsorption of low concentration ions in the secondary reverse osmosis effluent.The adsorption and exchange capacity of gel strong base resin is stronger than that of macroporous weak base ion exchange resin in low concentration solution.The adsorption capacity of gel strong base resin is higher than that of macroporous weak base resin.The adsorption capacity of the gel resin is weakened at low temperature,whereas the adsorption capacity of the large pore resin is weakened at high temperature.The adsorption of Clby 201×7 resin conforms to Freundlich adsorption isotherm.Two kinds of ion-exchange resins(001×7 and 201×7)were loaded into a mixed bed to conduct dynamic desalination experiments on simulated secondary reverse osmosis effluent.The experimental results show that the increase of process flow rate will lead to the decline of initial desalination effect.Different resin filling ratio will affect the initial desalination effect of the mixed bed.When the ratio of cation exchange resin is large,the breakdown volume of the mixed bed will decrease.The higher the regeneration velocity,the worse the regeneration effect of resin in mixed bed.Proper concentration of regeneration solution is helpful to the regeneration of mixed bed resin without waste of regeneration solution.When 50BV/h of water production stage is selected,anion exchange resin: cation exchange resin =1.5:1,regeneration solution is 3%Na OH solution,regeneration flow rate is 15BV/h,conductivity is 10μS /cm as the breakdown volume of mixed bed,water production is 1250 BV per cycle,and the total running time is 50 hours.Some ions still exist in the water produced by ion-exchange mixed bed.The electrodeionization process was used to desalinate the water produced by the mixed bed.The experimental results of continuous three-unit electrodeionization operation show that the current efficiency of the membrane reactor decreases gradually with the decrease of ion concentration in the fresh water chamber.The increase of the flow rate in the fresh water chamber can enhance the mass transfer,improve the removal rate and reduce the energy consumption in the membrane reactor operation.The increase of operating voltage of the device has no significant effect on the removal rate.The higher the operating voltage is,the more severe the reaction of hydrolysis is,and the greater the energy consumption of the device is.When the flow rate of the fresh water chamber is 200ml/min and the voltage at both ends of the membrane pile is 20 V,the conductivity of water production in the fresh water chamber is 0.262μs/cm,and the desalination rate is 98%.