Electrodialysis (ED) is an electrochemical separation process designed to transport salt ions from a less concentrated solution (diluate) to a more concentrated solution (concentrate) through the application of an electric current. The core of an ED system is an electrodialysis cell or stack, which houses a series of alternating anion exchange membranes (AEMs) and cation exchange membranes (CEMs) positioned between a cathode and an anode as shown in Figure 1. When a direct current (DC) electric field is applied across these electrodes, positively charged cations are drawn towards the negatively charged cathode, passing selectively through CEMs. Simultaneously, negatively charged anions migrate towards the positively charged anode, permeable only through AEMs. This differential migration results in a reduction of salt concentration in alternating compartments, yielding desalinated water, while the adjacent compartments accumulate the removed ions, forming a concentrated brine stream. ED is a relatively energy efficient and is particularly suitable for brackish water desalination where feed salinity is below 5,000 ppm.

An ED-related technology is electrodialysis reversal (EDR) that uses the same hardware with minor differences. EDR operates analogously to ED but the polarity of the electrodes is periodically reversed to prevent membrane scaling and fouling.

ED/EDR are used for desalination of brackish water, industrial process water treatment and it has also been used for concentration of seawater for salt production in Japan. It has also been used for industrial applications like industrial applications, including the demineralization of whey in dairy plants, sugar demineralization, recycling of pickling baths, various pharmaceutical processes, wine stabilization, desalting of glycerine and amines, and deacidification of fruit juices.