ELECTRODIALYSIS

"A process to move ions from one solution into another using an electrolytic cell. An example is the electrochemical desalination of seawater. In its simplest form, the cell is separated into three compartments by appropriate ion-exchange membranes with electrodes placed in the two outer compartments, and all compartments are fed seawater. As an electrical current is forced through the cell, anions will move from the central compartment through an anion-exchange membrane into the anode compartment and the cations will move through an cation-exchange membrane into the cathode compartment. Since the ion-exchange membranes are appropriately ion selective, the ions cannot move from the edge compartments to the central compartment, resulting in a desalinated effluent from that compartment. In practice, more than one cell will be connected in series, and the process will be carried out in several stages since it would not be efficient to remove all the salt in one step. This process is also used to remove industrial pollutants from waste streams. "