New application of EDI electric desalination

EDI is a pure water manufacturing technology that combines ion exchange technology, ion exchange membrane technology and ion electromigration technology. It cleverly combines electrodialysis and ion exchange technology, uses the high pressure of electrodes at both ends to move charged ions in water, and cooperates with ion exchange resin and selective resin membrane to accelerate the removal of ions, so as to achieve the purpose of water purification. During EDI desalination, ions are removed through an ion exchange membrane under the action of an electric field. At the same time, the water molecules generate hydrogen ions and hydroxide ions under the action of the electric field, and these ions continuously regenerate the ion exchange resin to keep the ion exchange resin in the best condition.

The desalination rate of EDI facilities can be as high as 99% or more. If the water is initially desalinated by reverse osmosis equipment before EDI, and then desalinated by EDI, ultrapure water with a resistivity of more than 18M.cm can be produced.

The EDI membrane stack is composed of a certain number of units sandwiched between two electrodes. Within each unit there are two different types of chambers: a fresh water chamber to be desalinated and a concentrated water chamber to collect the removed impurity ions. The fresh water chamber is filled with mixed cation and anion exchange resins, which are located between two membranes: a cation exchange membrane that allows only cations to pass through and an anion exchange membrane that allows only anions to pass through.

The resin bed is continuously regenerated by direct current applied to both ends of the chamber. The voltage decomposes the water molecules in the influent water into H+ and OH-. These ions in the water are attracted by the corresponding electrodes and pass through the cation and anion exchange resins to the corresponding membrane. When these ions pass through the exchange membrane and enter the concentration chamber, H + and OH- combine into water. The generation and migration of H+ and OH- is the mechanism by which the resin can be continuously regenerated.

When the 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 in the ordinary mixed bed, and correspondingly replace H+ and OH-. Once the impurity ions in the ion exchange resin are also added to the migration of H+ and OH- towards the exchange membrane, these ions will continuously pass through the resin until they pass through the exchange membrane and enter the concentrated water chamber. These impurity ions cannot migrate further towards the direction of the corresponding electrode due to the blocking effect of the adjacent compartment exchange membrane, so the impurity ions can be concentrated in the concentrated water chamber, and then the concentrated water containing impurity ions can be discharged from the membrane stack.

System Features:

  • The water quality is high and stable.
  • Continuous and uninterrupted water production, no shutdown due to regeneration.
  • No chemical regeneration required.
  • Imagine a thoughtful stackable design with a small footprint.
  • Simple and safe operation.
  • Low operating and maintenance costs.
  • No acid-base storage and transportation costs.
  • Fully automatic operation, no need for special care.

Application areas:

  • Power Plant Chemical Water Treatment
  • Ultrapure water for electronics, semiconductor and precision machinery industries
  • Process water for the pharmaceutical industry
  • Preparation of food, beverages and drinking water
  • Desalination of sea water and brackish water
  • Water for fine chemicals and advanced disciplines
  • High-purity water preparation required by other industries

Xi’an CHIWATEC Water Treatment Technology is a high-tech enterprise specialized in various water processing devices. Aside from these individual products, which cover a number of types and series, we can also help with related comprehensive engineering projects. Thanks to our hard work and dedication upon our founding, we are now one of the fastest-developing water treatment equipment manufacturers in Western China.

Further reading:

EDI equipment

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