Electrodialysis

Salt ions are moved via ion-exchange membranes from one solution to another using electrodialysis (ED), which is influenced by an applied electric potential difference. This is carried out in an arrangement known as an electrodialysis cell. An anion exchange membrane and a cation exchange membrane are positioned between two electrodes to create the feed (dilute) and concentrate (brine) compartments, respectively. With alternating anion and cation-exchange membranes creating the multiple electrodialysis cells, multiple electrodialysis cells are organised into a configuration known as an electrodialysis stack in practically all practical electrodialysis operations. Reverse osmosis (RO) and other membrane-based processes, like as distillation, vary from electrodialysis procedures in that dissolved species are transported away from the feed stream rather than toward it. Electrodialysis gives the practical benefit of substantially better feed recovery in many applications since the amount of dissolved species in the feed stream is much lower than that of the fluid. The effectiveness of ions being transported across ion-exchange membranes for a specific applied current is measured by the current efficiency. In commercial stacks, current efficiencies >80% are often preferred to save energy running expenses. Low current efficiency might be caused by back-diffusion of ions from the concentrate to the diluate, shunt currents between the electrodes, or water splitting in the dilute or concentrate streams.