This method is used for the desalination of water i.e., for the removal of dissolved mineral salts, acids, alkalis and also the radioactive substances from the effluents. Electro dialysis is performed in a multi-chamber membrane apparatus, known as electrodialyser, under the influence of electric current.
An electrodialyser is divided by alternating cation exchange and anion exchange membranes into concentrating and desalinating chambers.
These members have fixed charge-negative or positive-whereby they become impermeable to either anions or cations. Under the influence of electric field the cations motion to the cathode penetrate through the cation exchange membranes and retained by anion exchange membranes while the anions moving to the cation exchahge membranes and are retained by cation exchange resins . As a result, the ions of both the charges are removed from one row or chamber and desalinated water from the other.
This technique is useful for the production of fresh water on arid-coastal regions. In Japan, electrodialysis eg sea-water is the principal source of salt.