Summary
An electro dialysis unit is a water treatment technology that utilizes the selective permeability of ion exchange membranes to selectively direct the migration of ions in water under the influence of a direct current electric field, separating the cations and anions in the solution. 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 permits anions to pass through and blocks 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.
Primary 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 (as oxygen, potassium permanganate method)

Electrodialysis units utilize the electro-osmotic phenomenon to facilitate the migration of ions in the electrolyte solution within the compartments of the unit. This process allows for the separation of cations and anions, thereby 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 unit, which are equipped with alternating cation and anion exchange membranes and freshwater/brine separator plates, the direct current field induces ion migration. Chloride ions migrate towards the anode, while sodium ions migrate towards the cathode, as depicted in the diagram. Due to the selective permeability of the ion exchange membranes, the anion exchange membrane only allows anions to pass through, and the cation exchange membrane only allows cations to pass through. Consequently, 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 within the concentration compartment, causing the concentration within the compartment to gradually increase while the salt content in the dilution compartment decreases. The electrodialysis unit is composed of alternating layers of dilution and concentration compartments, with half being dilution compartments and the other half being concentration compartments. Water from each compartment is collected through specially designed channels at the edges of the separator plates, forming a freshwater and brine system, thereby achieving desalination.
Electrolytic dialysis (ED) unit composition
Electrodialysis equipment consists of a power supply converting AC to DC, an electrodialyzer, cleaning units, and more. The main components of the electrodialyzer include an anion exchange membrane (abbreviated as "anion membrane"), a cation exchange membrane (abbreviated as "cation membrane"), diaphragms, electrodes, and clamping devices. The compartments formed by the diaphragms serve as channels for the liquid flow. By alternating the anion membrane, cation membrane, and brine/freshwater diaphragms, adding a pair of electrodes, and then securing them, an electrodialyzer is assembled.

The electro dialysis membrane separator driven by an electric pump should operate normally under the following water quality conditions of the incoming water:
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 divider  <3 degrees
0.5mm to 0.9mm Separator    <1°