Electrodialysis

Electrodialysis separates dissolved ions by driving them through ion-selective membranes with an electric field. Alternating membranes create streams that become depleted or enriched in salts.

Cation-exchange membrane: A membrane that preferentially transports positively charged ions while restricting negatively charged ions. It carries cations across the stack while rejecting anions.
Desalination: The removal of dissolved salts from water to produce water with lower salinity. Electrodialysis is a desalination option, particularly for brackish feeds.
Reverse osmosis: A pressure-driven membrane process that removes dissolved substances by forcing water through a semipermeable membrane. Unlike electrodialysis, it primarily transports water rather than selectively moving ions.
Ion: An atom or molecule with a net electric charge from losing or gaining electrons. Electrodialysis transports these charged species rather than neutral solutes.
Monovalent-selective membrane: An ion-exchange membrane designed to favor monovalent ions over multivalent ions. Greater selectivity could improve separations such as sodium from calcium.
Anion-exchange membrane: A membrane that preferentially transports negatively charged ions while restricting positively charged ions. Alternating it with cation-exchange membranes creates ion-depletion and ion-concentration channels.
Brackish water: Water with salinity between that of freshwater and seawater. Its moderate salt content often suits electrodialysis better than seawater does.
Ion exchange: A separation process in which ions in solution exchange with ions attached to a solid material. It uses reversible binding sites instead of continuous electrical migration through membranes.
Electrolyte: A substance that forms mobile ions when dissolved or molten and can conduct electricity. Mobile ions in the feed carry current through the membrane compartments.
Membrane fouling: The accumulation of unwanted material on or within a membrane that impairs its performance. Fouling can raise resistance and reduce ion-transfer rates during operation.

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