Electrodeionized water purification technology is a new desalination process that combines electrodialysis and ion exchange. abbreviated as EDI.
Since the 1950s, the United States Walters and others have first discussed the process of electrodeionization and used it to concentrate radioactive wastewater, but its application in the field of water treatment and desalination has not made much progress. More than 30 years later, Millipore Company launched The first electric deionized water purifier named IonpurTMDI; at the same time, the ELIX component working on the principle of electrodeionization was developed, and it was put on the international market together as a Milli-RXTM analytical grade pure water purifier accessory. In 1990, Ionpure Company Manufactured improved components . In recent years, the Canadian company E-Cell has also launched the EDI product component E-CellTM and combined it into a complete set with a maximum water production of 450m3/h. It is reported that EDI desalination and mixed bed are currently used. In comparison, the prices of the two have been comparable in the world. The number of users using EDI desalination has grown exponentially over the years. The electrodeionized water purification technology has been industrially applied and promoted in the field of water treatment desalination.
EDI, in addition to continuous water output, one does not need chemical agents (acids, alkalis, salts) to regenerate, so as not to pollute the environment; two can be unattended, thereby creating conditions for automation; three wide adaptability, which can be used in various walks Industrial water treatment; Fourth, low operating cost, good economy, easy to popularize. The demonstration and analysis of some foreign experts  show that in today’s water treatment desalination system, the combined process of reverse osmosis (RO) and EDI can be used. Ensure that the best water treatment process performance is obtained, and its economy is not bad.It provides good development prospects for the promotion of this combined process.
In the process of preparing ultrapure water by general electrodialysis desalination treatment, when the concentration of electrolyte ions in the fresh water chamber solution is extremely low, the electrodialysis process is difficult to continue. When the electrolyte concentration is too low, the solution resistance increases , Power consumption increases, efficiency decreases, so that in fact, general electrodialysis desalination cannot be used to produce high-quality pure water. Usually, electrodialysis desalination and ion exchange combined desalination are used to prepare ultrapure water, which is electrodialysis as Pre-treatment, rough processing of desalination, use it to remove 80% to 90% of the salt content of the raw water, and then use ion exchange as a finishing process to remove the remaining 10% to 20%. In this way, it can play the role of electrodialysis The advantages of low energy consumption for desalination, no use of acids and alkalis, no pollution, and low cost of water production have reduced the burden of ion exchangers. Therefore, the working cycle of ion exchangers is extended, the number of regenerations is reduced, and the total consumption of regenerant is large The range is reduced, energy is saved, and the discharge of waste acid and alkali is greatly reduced. This electrodialysis and ion exchange combined desalination is a series combination of the two appearances.
Packed bed electrodialysis is another kind of combination, that is, the internal synthesis of electrodialysis and ion exchange.The so-called packed bed electrodialyzer is a fresh water chamber in the electrodialyzer filled with yin and yang mixed ion exchange Agents (particles, fibers, or braid), electrodialysis and ion exchange are placed in a container, and the two are internally integrated into one. Because the conductivity of the ion exchanger in pure water is higher than the general contact water 2 ~3 orders of magnitude, because the exchange agent particles continuously exchange and regenerate to form an “ion channel”, as a result, the conductivity of the fresh water chamber system (solution, exchanger and membrane) is greatly increased, thereby weakening the electrodialyzer The polarization phenomenon improves the limit current of the electrodialyzer and achieves a high degree of desalination.