Bipolar Membrane Electrodialysis Strengthens The Regeneration Of Electrodeionization Resins

Ammonia nitrogen and fluoride ions are inorganic ions existing in drinking water sources in many areas of China.Ammonia nitrogen will be oxidized to nitrate.Long-term drinking will lead to methemoglobinosis.Excessive fluoride in water will lead to dental fluorosis,skeletal fluorosis and other diseases,seriously affecting human health.Therefore,it is very important to remove ammonia nitrogen and fluoride ions in drinking water.Ion exchange method is an effective method to remove low concentration of pollutants,but there are some problems such as low regeneration efficiency and secondary pollution caused by using acid-base reagent and salt solution.In this paper,ion exchange resin(NA)and Amberlite(?) IRA-900 anionic resin were used to remove ammonia nitrogen and fluoride from drinking water.The properties of the resin enhanced by bipolar membrane electrodialysis were studied.The optimal conditions and influencing factors of resin regeneration were discussed.The research contents and conclusions are as follows:(1)Ammonia nitrogen removal by cation exchange resin can reach adsorption equilibrium within 60 min,and the removal rate can reach more than 90.0%.The effects of voltage,concentration chamber solution,pH value of resin chamber solution,resin adsorption capacity and coexisting ions on the regeneration of electrodeionized resin enhanced by bipolar membrane electrodialysis were studied.The results show that when the voltage is15 V,the optimal regeneration rate is 48.5% and the energy consumption is 7.71 W·h/mg.When 0.01 mol/L HCl was added into the circulating solution in the resin chamber,the regeneration rate of the resin was increased to 55.4%.Compared with the regeneration rate of HCl only 0.5%,the regeneration rate of the bipolar membrane electrodialysis enhanced electrodeionization regeneration resin was increased 102 times.The regeneration rate of the resin was reduced to 45.5%.(2)Anion exchange resin can remove 94.0% fluorine ions in water containing fluorine(2mg/L).The effects of device voltage,electrode solution,concentration chamber solution,pH value of resin chamber solution,resin adsorption capacity and coexisting ions on the regeneration of electrodeionized resin enhanced by bipolar membrane electrodialysis were studied.The results show that when the voltage is 15 V,the regeneration effect reaches62.4%,and the energy consumption is only 1.65 W·h/mg.When 0.01 mol/L NaOH was added into the circulating solution in the resin chamber,the regeneration time of anion exchange resin was reduced from 300 min to 180 min,and the regeneration rate was increased to 83.3%.Compared with the regeneration effect of NaOH only 5.2%,the regeneration rate of anion exchange resin was increased by 16 times.Phosphoric acid is more difficult to desorbed than fluorine ion,and the regeneration rate of resin adsorbed fluorine ion and phosphoric acid at the same time is reduced to 50.8%,and the regeneration time is increased to 360 min.(3)In the "back to back" way,the use of bipolar membrane electrodialysis to strengthen the electrodeionization and regeneration of ion exchange resin.The effects of device voltage,combination of pH value of circulating liquid in resin chamber,resin adsorption capacity and coexisting ions on resin regeneration were discussed.The results show that the optimal regeneration voltage increases from 15 V to 20 V when cation exchange resin and anion exchange resin is treated simultaneously.The regeneration of resin was shortened from 480 min to 360 min by adding cyclic solutions with different pH values in the resin chamber.The energy consumption per unit is only 5.92 W·h/mg,which is far lower than the total energy consumption(10.28W·h/mg)of regenerated cation exchange resin and anion exchange resin.This paper provides theoretical and technical support for resin regeneration by bipolar membrane electrodialysis enhanced electrodeionizat-ion technology.