What Issues Should Be Considered When Choosing Electrodialysis?

I. Electrodialysis uses electrical energy to migrate and separate ions. When the salt content in water is low, the resistivity of the water is high, and the limiting current value of the electrodialysis unit is also low. Electrodialysis is prone to polarization during operation. Therefore, it is generally considered suitable for water with a salt content of less than 10-50 mg/L. Unlike ion exchange, it cannot achieve deep desalination to obtain ultrapure water.

II. Electrodialysis is difficult to remove salts with low degrees of dissociation and non-dissociated substances. For example, it cannot remove silicate from water, has a low migration rate for carbonate ions, and cannot remove non-dissociated organic matter. Unlike ion exchange, it cannot remove silicates, and unlike reverse osmosis, it removes a much wider range of substances.

III. Certain high-valence metal ions and organic matter can foul ion exchange membranes, reducing desalination efficiency.

IV. Electrodialysis units consist of tens to hundreds of extremely thin septa and membranes. With many components and complex assembly, a problem in one component can affect the entire unit.

V. Electrodialysis involves passing water through an electric field. When a certain voltage is applied, the electrolyte content in the water near the membrane becomes extremely low, which increases the degree of water dissociation and makes it prone to polarization, scaling, and neutrality disturbance. This is a difficult problem to control but must be taken seriously in the operation of electrodialysis.