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/anode electrodes are set at both ends of the unit group. Driven by the direct current, the anions and cations in the water flow through the fresh water chamber respectively pass through the anion and cation exchange membrane into the concentrated water chamber and are removed in the fresh water chamber. The water passing through the concentrated water chamber brings 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). EDI pure water resistivity can be as high as 18 MΩ.cm (25℃), but according to the use of deionized water and system configuration settings, 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 and more extensive.
In recent decades, the mixed bed ion exchange technology has been the standard process for the preparation of ultrapure water. Because it needs periodic regeneration and a lot of chemicals (acid and alkali) and pure water are used in the regeneration process, and cause certain environmental problems, it is necessary to develop an acid and alkali-free ultrapure water system.
Because traditional ion exchange has become increasingly unable to meet the needs of modern industry and environmental protection, the EDI technology that combines membrane, resin and electrochemical principles has become a revolution in water treatment technology. The regeneration of the ion exchange resin uses electricity instead of acid and alkali, so it is more satisfied with the environmental protection requirements of the world today.
Since the industrialization of EDI membrane stack technology in 1986, thousands of EDI systems have been installed all over the world, especially in the pharmaceutical, semiconductor, electric power and surface cleaning industries, as well as in the fields of wastewater treatment, beverages and microorganisms. It is also widely used.