What is EDI ultra-pure water technology?

EDI (continuous EDI) is a pure water manufacturing technology that combines ion exchange technology, ion exchange membrane technology and ion electromigration technology. It skillfully combines electrodialysis with ion exchange technology, uses the high voltage of two electrodes to move charged ions in water, and cooperates with ion exchange resin and selective resin membrane to accelerate the removal of ions, thus achieving the purpose of purifying water. In EDI desalination process, ions are removed by ion exchange membrane under the action of electric field. At the same time, water molecules generate hydrogen ions and hydroxide ions under the action of electric field, and these ions constantly regenerate the ion exchange resin, so that the ion exchange resin keeps the best state. The desalination rate of EDI equipment can be as high as 99%. If the water is preliminarily desalted by reverse osmosis equipment before EDI, it is ultra-pure water with high resistivity above 15M. Cm can be produced by EDI. EDI membrane stack consists of many units sandwiched between two electrodes. There are two different types of chambers in each unit: the fresh water chamber to be desalted and the concentrated water chamber to collect the removed impurity ions. The fresh water chamber is filled with mixed cation exchange resin and anion exchange resin, which are located between two membranes: the cation exchange membrane which only allows cations to pass through and the anion exchange membrane which only allows anions to pass through. The resin bed is continuously regenerated by direct current applied to both ends of the chamber. Voltage decomposes water molecules in water into H+ and OH-. These ions in water are attracted by the corresponding electrodes and migrate to the corresponding membrane direction through cation-anion exchange resin. When these ions enter the concentration chamber through the exchange membrane, H+ and OH- combine to form water. This generation and migration of H+ and OH- is the mechanism of continuous regeneration of resin. When impurity ions such as Na+ and CI- in the influent are adsorbed on the corresponding ion exchange resin, these impurity ions will undergo the same ion exchange reaction as the common mixed bed, and H+ and OH- will be replaced accordingly. Once the impurity ions in the ion exchange resin are added to the migration of H+ and OH- to the exchange membrane, these ions will continue to pass through the resin until they enter the concentrated water chamber through the exchange membrane. Due to the blocking effect of exchange membranes in adjacent compartments, these impurity ions cannot migrate further to the corresponding electrodes, so the impurity ions are concentrated in the concentrated water chamber, and then the concentrated water containing the impurity ions can be discharged from the membrane stack. For decades, the preparation of pure water was at the cost of consuming a lot of acid and alkali. In the process of production, transportation, storage and use, acid and alkali will inevitably bring pollution to the environment, corrosion to equipment, possible harm to human body and high maintenance costs. The use of reverse osmosis greatly reduces the amount of acid and alkali, but there are still weak electrolytic ions. The wide application of reverse osmosis and electric desalting will bring an industrial revolution to the preparation of pure water. The working principle of EDI tap water often contains dissolved salts such as sodium, calcium, magnesium, chlorine, nitrate and silicon. These salts consist of negatively charged ions (negative ions) and positively charged ions (positive ions). Reverse osmosis can remove more than 99% ions. Tap water also contains trace metals, dissolved gases (such as carbon dioxide) and other weakly ionized compounds (such as silicon and boron), which must be removed in industrial treatment. RO reverse osmosis effluent (EDI influent) is generally 60-40μ m/cm (conductance). According to different needs, the general resistance of ultra-pure water or deionized water is 2-18mΩ micron ... The exchange reaction is carried out in the pure chemistry room of the module, and anion exchange resin exchanges anions (such as chloride ion C 1) in the dissolved salt with its hydroxide ion (OH-). Therefore, the cation exchange resin exchanges its hydrogen ions (H+) into cations (such as Na+) in dissolved salts. A DC electric field is applied between the anode (+) and the cathode (-) at both ends of the module. This potential causes the ions exchanged on the resin to migrate along the surface of the resin particles and enter the concentrated water chamber through the membrane. The anode attracts negative ions (such as OH- and cl-), which enter the adjacent concentrated water flow through the anion membrane, but are blocked by the cation selective membrane, thus remaining in the concentrated water flow. Cathode attracts cations (such as H+ and Na+) in pure water. These ions pass through the cation selective membrane and enter the adjacent concentrated water stream, but are separated by the anion membrane, thus remaining in the concentrated water stream. When water flows through these two parallel chambers, ions are removed in the pure water chamber and accumulated in the adjacent concentrated water flow, and then are carried away from the module by the concentrated water flow. The application of ion exchange resin in pure water and concentrated water is the key of electrophoresis technology and patent. An important phenomenon occurs in the ion exchange resin in the pure water chamber. In the local area with high potential difference, the water decomposed by electrochemical reaction produces a large number of H+ and OH-. The local generation of H+ and OH- in the mixed bed ion exchange resin enables the resin and membrane to be continuously regenerated without adding chemicals. The basic requirement of EDI trouble-free in the best working state is proper pretreatment of EDI water inlet requirements. Impurities in the influent have a great influence on the deionization module. And may lead to a shortened module life. System features ⊙ The quality of produced water is high and stable. ⊙ Continuous production of water will not stop because of regeneration. No chemical regeneration is needed. Intimate stacked design, small floor space. ⊙ Simple and safe operation. ⊙ Low operating and maintenance costs. No acid-base reserves and transportation costs. ⊙ Fully automatic operation, no need for unattended operation. The development of pure water treatment technology mainly experienced anion and cation exchanger+mixed ion exchanger; Reverse osmosis+mixed ion exchanger; Reverse osmosis+electrodeionization device and other stages; Pretreatment+reverse osmosis+continuous electric desalting. The whole desalting system has incomparable advantages over other treatment systems and is widely used in the preparation of pure water and high purity water. Application fields ⊙ Chemical water treatment in power plants ⊙ Ultra-pure water in electronics, semiconductors and precision machinery industries ⊙ Process water in pharmaceutical industry ⊙ Preparation of food, beverage and drinking water ⊙ Desalination of seawater and brackish water ⊙ Water for fine chemicals and precision disciplines ⊙ Preparation of high-purity water needed by other industries ⊙ 𕬙.