English: Scheme of an electrodialyzer. A solution of salt passes between alternately placed cation- and anion-exchange membranes placed between charged electrodes. Cations migrate towards negatively charge cathode, they pass through cation-exchange membrane, but are stopped by the anion-exchange membrane. Anions migrate towards positively charged anode, they pass through anion-exchange membrane, but are stopped by the cation-exchange membrane. The result is one part of the feed is desalted (so-called diluate), while the second is concentrated (so-called concentrate).