EDI is a process which combines semipermeable membrane technology with ion-exchange media to provide a high efficiency demineralization process.
An EDI stack has the structure of a deionization chamber. This chamber contains an ion exchange resin, packed between a cationic exchange membrane and an anionic exchange membrane. In this process, only the water can pass through the membrane as the ions are blocked.
Several processes are in motion when the flow of water enters the resin filled diluting compartment. The mixed bed resins scavenge the strong ions out of the feed stream. Under this influence of the strong direct current field, charged ions are pulled off from the resin and drawn towards the respective, oppositely-charged electrodes. In this way these charged strong-ion species are continuously removed and transferred into the adiacent concentrating compartments – dividing the clean water and impurities.