Summary
An electro dialysis unit is a water treatment technology that utilizes the selective permeability of ion exchange membranes to cause ions in water to migrate selectively in a direct current electric field, separating the positive and negative ions in the solution. It is a physical and chemical process. Due to its low energy consumption, high water production, high desalination rate, and strong stability, it is used in various fields such as electronics, chemicals, food processing, hard water softening, and seawater desalination.
Operating Principle
The key component of an electro dialysis unit is the ion exchange membrane, which comes in two types: cation exchange membrane (positive membrane) and anion exchange membrane (negative membrane). The positive membrane allows cations in the solution to pass through while blocking anions, while the negative membrane allows anions to pass through while blocking cations. Under the influence of an external electric field, ions in water move selectively in a directional manner, resulting in a reduction of ion count in some water and an increase in others, thereby achieving desalination.
Key Technical Parameters
Turbidity < 1 mg/L
Total Iron Content < 0.3 mg/L
Total Manganese Content < 0.1 mg/L
Water temperature: 5-40℃
Chroma < 20℃

Oxygen Demand < 2 mg/L (measured by potassium permanganate)

Electrodialysis separators utilize the electrodialysis phenomenon to facilitate ion migration within the compartments of the separator, allowing cations and anions in the electrolyte solution to pass through cation and anion exchange membranes, respectively, achieving the objectives of dilution and concentration. Taking sodium chloride as an example, when a sodium chloride water solution passes through the compartments of an electrodialysis separator equipped with alternating cation and anion exchange membranes and freshwater/densewater separators, ion migration occurs under the influence of a direct current field. Chloride ions migrate towards the anode, while sodium ions migrate towards the cathode, as illustrated. Due to the selective permeability of the ion exchange membranes, the anion exchange membrane only allows anions to pass, and the cation exchange membrane only allows cations to pass. Therefore, cations in the dilution compartment migrate towards the cathode, passing through the anion membrane into the concentration compartment, while anions in the dilution compartment migrate towards the anode, passing through the cation membrane into the concentration compartment. In the concentration compartment, the cations and anions also migrate towards the cathode and anode, respectively, under the influence of the direct current field. However, due to the阻挡 of the ion exchange membranes on both sides of the compartment, they remain in the concentration compartment, causing the concentration in the concentration compartment to gradually increase and the salt content in the dilution compartment to gradually decrease. The electrodialysis separator is composed of alternating layers of dilution and concentration compartments, with half being dilution compartments and the other half being concentration compartments. Water flows from each compartment are collected through specially designed channels at the edges of the separators to form separate systems of concentrated and diluted water, thereby achieving desalination.
Electrodialysis (ED) Unit Components
Electrodialysis equipment consists of a power supply converting AC to DC, an electrodialyzer, a cleaning unit, and more. The main components of the electrodialyzer include an anion exchange membrane (referred to as the anion membrane), a cation exchange membrane (referred to as the cation membrane), diaphragms, electrodes, and clamping devices. The compartments formed by the diaphragms serve as channels for the liquid flow. By alternating the arrangement of the anion membrane, cation membrane, and diaphragms separating brine and freshwater, adding a pair of electrodes, and then clamping them together, an electrodialyzer is formed.

Electrodialysis membrane separators driven by an electric pump should operate normally under the following incoming water quality conditions:
Water Temperature: 5-40℃
b. Manganese Dioxide Index <3 mg/L
c. Free Chlorine               <0.2 mg/L
d. Iron < 0.3 mg/L
e. Manganese                 <0.1 mg/L
f. Turbidity  1.5mm to 2.0mm separator <3 degrees
0.5mm to 0.9mm Separator <1 Degree