Electrodialysis

Under the influence of an applied electric potential difference, electrodialysis (ED) is used to transfer salt ions from one solution to another using ion-exchange membranes. An electrodialysis cell is the setting in which this is carried out. The cell is made up of two compartments—a feed (dilute) compartment and a concentrate (brine) compartment—that are produced by cation exchange and anion exchange membranes that are sandwiched between two electrodes. Numerous electrodialysis cells are organised into a configuration known as an electrodialysis stack in practically all practical electrodialysis procedures. The numerous electrodialysis cells are made up of alternating anion and cation-exchange membranes. Since dissolved species are transported away from the input stream rather than toward it, electrodialysis operations differ from distillation methods and other membrane-based processes (such reverse osmosis (RO). The practical benefit of electrodialysis in many applications is a substantially greater feed recovery since the amount of dissolved species in the feed stream is far lower than that of the fluid. How efficiently ions are transferred across ion-exchange membranes for a specific applied current is determined by the term "current efficiency." To reduce energy operation expenses, commercial stacks should typically have current efficiencies >80%. Shunt currents between the electrodes, back-diffusion of ions from the concentrate to the diluate, water splitting in the dilute or concentrate streams, or low current efficiency might all be at play.