EDI system is a process that mixed ion exchange resin is used to adsorb anions and cations of water supply, and at the same time, under the action of DC voltage, the adsorbed ions are removed through anion exchange membrane and cation exchange membrane respectively. ? Between a pair of electrodes of electrodialyzer, a certain number of EDI units are usually separated by a screen with a negative membrane to form a concentration chamber and a dilution chamber.
Cations in fresh water migrate to the negative electrode and pass through the positive electrode membrane, and are intercepted by the negative electrode membrane in the concentration chamber; Anions in water migrate to the anode and are intercepted by the anode membrane in the concentration chamber; By arranging anion/cation exchange membranes at both ends of the unit group, they respectively enter the concentrated water chamber to remove fresh water. Ions are taken out of the system by the water in the concentrated water chamber and become concentrated water. So as to achieve the purpose of desalination, purification, concentration or refining.
Extended data
EDI membrane stack is the core of EDI work. Membrane stack is a unit composed of anion and cation exchange membranes, strong and weak water chamber partitions, ion exchange resin and positive and negative electrodes arranged and clamped according to certain rules. The fresh water chamber in the membrane stack is equivalent to a mixed bed, and the ion exchange resins used are sulfonic acid cationic resin and quaternary ammonium anionic resin, and the resins in the fresh water chamber must be packed tightly.
EDI membrane stack system has two different types of chambers in each unit, namely, fresh water chamber to be desalted and concentrated water chamber to collect removed impurity ions. The fresh water chamber is filled with mixed anion exchange resin and cation exchange resin, which are located between the two membranes. The cation exchange membrane only allows cations to pass through, and the anion exchange membrane only allows anions to pass through.
Reference source; Baidu encyclopedia-EDI system composition
Reference source; Baidu encyclopedia-EDI system