EDI (Electro-de-ionization, continuous electro-de-ionization) is also called EDI and continuous electro-deionization. It is a process in which mixed ion exchange resins are used to adsorb the anions and cations in the water, and these adsorbed ions are removed by the exchange membrane through the anion and cation under the action of a direct voltage. In this process, the ion exchange resin is continuously regenerated by electricity, so there is no need to regenerate it with acid and alkali. This new technology can replace traditional ion exchange devices to produce ultrapure water with a resistivity of up to 18MΩ·CM.
EDI device fills the ion exchange resin between the anion/cation exchange membranes to form an EDI unit. In the EDI module, a certain number of EDI units are separated by a mesh to form a concentrated water chamber. The cathode and anode electrodes are set at both ends of the unit group. Driven by the direct current, the anions and cations in the water flowing through the fresh water chamber respectively pass through the anion and cation exchange membrane into the concentrated water chamber and are removed by the fresh water. The water passing through the concentrated water chamber takes the ions out of the system and becomes concentrated water.
EDI equipment generally uses reverse osmosis (RO) pure water as EDI feed water. The resistivity of RO pure water is generally 40-2μS/cm (25°C). The resistivity of EDI pure water can be as high as 18.2MΩ.cm (25℃), but according to the use of deionized water, EDI pure water is suitable for preparing pure water with a resistivity requirement of 1-18.2MΩ.cm (25℃).
EDI technology is generally accepted by the pharmaceutical industry, microelectronics industry, power generation industry and laboratories. The application in surface cleaning, surface coating, electrolysis industry and chemical industry is also becoming more extensive.