Electrodeionization
Electrodeionization (EDI) is a water treatment technology that utilizes electricity, ion exchange membranes, and resin to deionize water and separate dissolved ions (impurities) from it. It differs from other water purification technologies in that it is done without the use of chemical treatments and is usually a polishing treatment to reverse osmosis (RO). There are also EDI units that are often referred to as continuous electrodeionization (CEDI) since the electric current regenerates the resin mass continuously. CEDI technique can achieve very high purity, with a conductivity below 0.1 μS/cm. Electrodeionization (EDI) can be differentiated into three stages, so the basics of EDI reside in the simultaneity of the following processes. - Electrodialysis: with a continuously applied electric voltage, both positive and negative ions are directed to those electrodes that have a load opposite. The permeable membranes of anions and cations are responsible for directing them to the concentrated area. - Ion exchange: in the area between the different membranes is the resin that has different types of load. The salts present in the water adsorb onto the ion exchange resin, moving opposite to their load. Finally, they are replaced in resin exchange positions by hydroxyl anions and hydrogen cations. - Regeneration: the continuous regeneration is made by hydrogen ions and hydroxyl groups. This occurs due to the dissociation of the molecules of water that occurs in the anode and cathode when applying electric voltage (called water splitting). (Wikipedia).
