ELECTRODEIONIZATION (EDI)

EDI is a pure water manufacturing technology that combines ion exchange
technology, ion exchange membrane technology and ion electromigration
technology. It skillfully combines electrodialysis and ion exchange technology,
uses high voltage 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 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, which continuously
regenerate the ion exchange resin to keep the ion exchange resin in the best
state.

Technical Data of Electrodeionization Unit
Item Reference value
Nominal Recovery: 90–95%
EDI Water Quality: 15–18 MΩ.CM（25℃）
FEED CONDUCTIVITY (INCLUDING CO2): < 10 µs/cm（25℃）
Operating Temperature: 50–100° F
Maximum Inlet Pressure: 100 psig
Minimum Inlet Pressure: 60 psig
Expected Pressure Drop: 30–40 psig
Electrical Requirement: 380 VAC, 3-phase, 50 Hz.

OPERATING PRINCIPLES OF ELECTRODEIONIZATION

EDI Process

EDI desalination process is to exchange ions in water with hydroxide ions or
hydrogen ions in ion exchange resin, and then migrate these ions into
concentrated water；

The above exchange reaction takes place in the freshwater chamber of the
module. In the freshwater chamber, the hydroxide ion in the anion exchange
resin exchanges with the anion in the water, and the hydrogen ion in the cation
exchange resin exchanges with the cation in the water；

The exchanged ions migrate along the surface of the resin ball under the effect
of the DC electric field and enter the concentrated water chamber through the
ion exchange membrane；

The negatively charged anions are attracted by the anode, and these ions enter
the adjacent concentrated water chamber through the anion membrane, while the
adjacent cation membrane membrane does not allow them to pass through. These
ions are blocked in the concentrated water, while the positively charged
cations are attracted by the anion anion, and these ions enter the adjacent
concentrated water chamber through the cation membrane, while the adjacent
anion membrane does not allow them to pass through. These ions are blocked in
the concentrated water.

In concentrated water, ions from both directions maintain electric neutrality.
At the same time, the amount of current is proportional to the amount of ion
migration. The amount of current consists of two parts, one part from the
migration of removed ions, and the other part from the migration of water
itself ionized into H+and OH - ions；

When the water flow passes through the fresh water chamber and the concentrated
water chamber, the ions gradually enter the adjacent concentrated water chamber
from the fresh water chamber and are carried out of the EDI module by the
concentrated water；

Under the action of higher voltage gradient, water will generate a large amount
of H+and OH- through electrolysis. These generated H+and OH- will continuously
regenerate the ion exchange resin. Therefore, the ion exchange resin in EDI
module does not need chemical regeneration；

The above is the desalination process of EDI.

FEATURES OF ELECTRODEIONIZATION
1.
Regeneration of acid and alkali is not needed.

2.
Zero discharge; no discharge of wastewater.

3.
The running is continuous and the water quality is stable.

4.
Modularization design is adopted so as to facilitate extension.

5.
Less space is occupied.

If you want to know more kinds of electrodeionization system, please visit our
website.

The water system in pharma is based on the preparation equipment, storage and
export of purified water and water for injection and other functional units,
optimized and combined by various functional modules, so as to ensure the high
performance and quality of the whole system, and make the product water fully
meet or exceed the water quality standards of purified water and water for
injection.

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