Under the action of external direct current electric field, the selective transmissibility of the ion exchange membrane to the ions in the solution is utilized to make the solution negative and cationic ions migrate and reach the purpose of salt removal or concentration through the negative and cationic exchange membrane respectively.
Electrodialysis (ED) is a method for seawater desalination using ion exchange membrane.
Ion exchange membrane is a kind of functional membrane, which is divided into anion exchange membrane and cationic exchange membrane, [referred to as Yin membrane and Yang membrane].
The cationic membrane allows only cationic ions to pass through the anion membrane, which is the selective transmissibility of the ion exchange membrane.
Under the action of the applied electric field, the negative and positive ions in the aqueous solution will move to the anode and cathode respectively. If an exchange membrane is added in the middle, the purpose of separation and concentration may be achieved.
Electrodialysis takes advantage of this principle.