Elektrodeionisaatio

Elektrodeionisaatio, often abbreviated as EDI, is a continuous water demineralization process. It combines ion-exchange membranes and ion-exchange resins with an electric field to remove ions from water. The process is typically used for producing high-purity water, often as a final polishing step after initial treatments like reverse osmosis.

In an EDI module, alternating layers of cation-exchange membranes and anion-exchange membranes are used. Between these membranes are chambers filled with ion-exchange resin beads. When a DC electric field is applied, the ions in the water are attracted to their respective electrodes. Cations migrate through the cation-exchange membranes and are captured by the cation-exchange resin, while anions migrate through the anion-exchange membranes and are captured by the anion-exchange resin.

The ion-exchange resins are continuously regenerated by the electric field. As ions accumulate on the resin, the electric field drives them out of the resin and across the membranes into a concentrate stream. This continuous regeneration eliminates the need for chemical regeneration agents like acids and bases, making EDI an environmentally friendly and cost-effective solution for producing ultrapure water. The process is highly efficient in removing dissolved salts and other ionic impurities, achieving very low conductivity levels in the treated water. EDI is widely employed in industries such as semiconductor manufacturing, pharmaceuticals, and power generation where high-purity water is essential.