EDI ultrapure water system working principle and principle technology introduction

Reverse osmosis (RO) technology is a method that uses membrane separation to remove ions in water. Although the reverse osmosis system removes 95%-98% of ions in water, it cannot meet the requirements of industrial production. The subsequent processes must use ion exchange equipment. . In recent decades, the mixed bed ion exchange technology has been the standard process for the preparation of pure water. Because it needs periodic regeneration and uses a lot of chemicals (acid and alkali) and pure water in the regeneration process, it is difficult to be satisfied with the acid-alkali-free pure 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 and resin has become a revolution in water treatment technology. This technology uses electric regeneration ion exchange desalination process to replace the traditional mixed ion exchange desalination process DI. High desalination effect is achieved through ion exchange resin and selective ion membrane, and the combined process combined with reverse osmosis makes the water quality of 10~17M Ω·CM high specification water produced.

EDI is a new type of desalination technology formed by organically combining electrodialysis technology and ion exchange technology. It can effectively remove all ions in the water, the resistivity of the effluent can be stabilized above 15MΩ.CM, continuous operation, no chemical pollution, high water utilization, and has broad application prospects in the preparation of high-purity water. The EDI device is applied after the reverse osmosis system to replace the traditional mixed ion exchange technology (MB-DI) to produce stable deionized water.

Working principle of EDI ultrapure water system:

  1. Water enters the EDI system, and the main part flows into the resin/membrane, while the other part flows along the outside of the template to wash away the ions that penetrate the membrane.
  2.  The resin intercepts the dissolved ions in the water.
  3. Under the action of the electrode, the trapped ions move the anions towards the positive electrode and the cations towards the negative electrode.
  4. Cations permeate through the cation membrane and drain out of the resin/membrane.
  5. Anions permeate through the anion membrane and drain out of the resin/membrane.
  6. The concentrated ions are discharged from the waste water flow path.
  7. Non-ionized water flows out of the resin/membrane.

Compared with mixed ion exchange technology, EDI technology has the following advantages:

  1. Stable water quality
  2. Easy to realize fully automatic control
  3. No shutdown due to regeneration
  4. No need for chemical regeneration
  5. Low operating cost
  6. Small plant area
  7. No sewage discharge.

The development history of high-purity water treatment technology:

The first stage: pretreatment——> positive bed ——> negative bed ——> mixed bed
The second stage: Pretreatment——> Reverse Osmosis ——> Mixed Bed
The third stage: Pretreatment——>Reverse Osmosis——>EDI device

RO EDI water treatment

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