Technology

Electrodeionization modules are built using multiple layers of ion exchange membranes with the space between each membrane filled with ion exchange resin. The ion-exchange membranes are stacked up by alternating layers between those that pass only anions (anion exchange membrane) and those that pass only cations (cation exchange membrane). The layers are placed in between two electrodes and the stack connected to a power supply to create the electrical driving force for continuous deionization.
As feedwater moves into the stack in the dilute channel, the residual salts and ionizable aqueous impurities (such as carbon dioxide, silica, ammonia and boron) first attach to the ion exchange resin. The direct current electrical field between the electrodes moves anions through the anion exchange membrane toward the anode and into the next layer of ion exchange resin where it is trapped by the alternating use of the cation exchange membrane in what is called the concentrate channel. Conversely, the direct current electrical field moves cations through the cation exchange membrane in the opposite direction toward the cathode and where it is trapped again in a resin-filled concentrate channel by alternating use of anion exchange membrane. As the water moves through the stack in the dilute channel, impurities continue to be removed for the production of ultrapure or high purity water.