Study On Seawater Desalination And Removal Of Boron From Seawater By Electrodialysis

In the process of island development and construction,electrodialysis small seawater desalination technology has a strong advantage.However,the problem of high boring water content and high energy consumption in this technology needs to be further solved.In view of the above problems,this paper firstly simulates seawater in a laboratory configuration,and proposes a method of concentrated electrodialysis of concentrated water.The concentrated water in the electrodialysis process is discharged from one to five stages,and the salt and boron in the solution are investigated.Removal effect,such as pH value,resistance,current efficiency and water migration amount change;and we have an operation process optimization and improvement of factors affecting electrodialysis seawater desalination boron removal effect on electrodialysis time,pH value and ion exchange membrane type which has effect of boron removal during electrodialysis seawater desalination;and the establishment of a portable small seawater desalination equipment for field trials.The study found that:1.When using the concentrated water section electrodialysis method,the simulated seawater desalination rate increases with the number of concentrated water discharges from one to five segments;the salt content falls to the 500 mg required by the Drinking Water Quality Standard.The time required for /L is gradually shortened;the electromigration coefficient ? of the ion remains basically unchanged,and the diffusion coefficient ? of the ion decreases yearon-year;the electro-osmotic coefficient ? of the water remains substantially unchanged,and the concentration diffusion coefficient ? of the water gradually decreases.By decreasing,the amount of water loss in the light chamber due to the concentration difference between the desalinated and concentrate chambers also decreases as the number of segments increases.2.When the concentrated water is used for the out-of-step electrodialysis method,the fourstage concentrated water efflux method for simulating the removal of boron in seawater can simulate the concentration of boron in seawater within 180 minutes of electrodialysis from 5mg/L to 0.461mg/L,it meets the requirements of the Drinking Water Quality Standard.3.When using the concentrated water section electrodialysis method,the pH value of the desalinated room is increasing,but it can meet the pH value of the drinking water quality standard.At the same time,the electrodialysis membrane stack resistance is divided by the concentrated water.The number of rows increases and gradually slows down.The current efficiency of the electrodialysis membrane stack increases obviously,and the average efficiency is up to 90.4%.The energy consumption of the membrane stack is gradually reduced.The energy consumption of the four-stage concentrated water section electrodialysis is the lowest.4.Optimize the operation process for factors affecting the effect of electrodialysis seawater desalination.The results show that when the electrodialysis time is 210 min,the concentration of boron in the desalination chamber is the lowest,and the concentration of boron will rise after 210 min.When the pH in the desalination chamber is maintained at 8.5,the removal effect of boron in the desalination chamber is the best;When the dialysis process is carried out until 120 min,the pH of the desalination chamber is maintained at 8.5,and the boron concentration in the light chamber can be reduced from 5 mg/L to 0.3041 mg/L at the end of the experiment,thereby achieving the highest boron removal efficiency of the electrodialysis membrane stack;the Katsujiro Iwai ion exchange membrane is excellent in ion mobility,electromigration coefficient,concentration diffusion coefficient,water electro-osmotic coefficient,concentration permeability coefficient and boron removal effect,but its price is expensive,in order to reduce cost,we organized the portable small seawater desalination electrodialysis equipment using Hefei Kejia No.4 ion exchange membrane which is slightly inferior in performance.5.According to the laboratory research results,a portable small-scale seawater desalination electrodialysis equipment was set up,and the actual seawater desalination and boron removal verification test was carried out on an island to investigate the effect of seawater desalination and boron removal.The results show that the portable small seawater desalination electrodialysis equipment can meet the requirements of salt content and boron in the actual seawater desalination treatment,but the removal effect of boron is not stable enough.