ion exchange

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ion exchange

the process in which ions are exchanged between a solution and an insoluble solid, usually a resin. It is used to soften water, to separate radioactive isotopes, and to purify certain industrial chemicals

Ion Exchange


the exchange of ions in electrolytic solutions (homogeneous ion exchange). When dilute electrolytic solutions, such as NaCl and KNO3, are mixed, Na+, K+, NO3, and Cl ions are present in the mixture. The state of equilibrium for this case is expressed by the equation NaCl + KNO3 ⇄ NaNO3 + KCl (double-exchange reaction). If one of the substances produced during the interaction is less dissociated than the others, the equilibrium shifts toward the formation of the poorly dissociated substance. The equilibrium also shifts toward the formation of a volatile or poorly soluble product (if it is precipitated from the particular phase) according to the reactions

H2SO4 + 2KCN ⇄ K2SO4 + 2HCN ↑

NaCl + AgNO3 ⇄ NaNO3 + AgCl↓ I

The crystallization of a salt (ion combination), which has lower solubility, is the first process to take place upon evaporation of an equilibrium solution. The selectivity of crystallization may also be caused by the addition of organic solvents, such as alcohol, acetone, or dioxane.

During heterogeneous ion exchange (ion-exchange sorption), exchange takes place between ions that are in solution and those that are on the surface of the solid phase (the ion exchanger). When an ion exchanger saturated with one ion (such as H+) comes into contact with a solution containing other ions (for example, Na+ and Ca2+), ion exchange occurs between the ion exchanger and the solution: the concentration of Na+ and Ca2+ in the solution is reduced, and an equivalent quantity of H+ ions appears.

Heterogeneous ion exchange takes place during sorption of certain minerals (aluminosilicates, metallic hydroxides, and zeolites) from electrolytic solutions in the cells and membranes of living organisms and in synthetic ion-exchange sorbents. This type of ion exchange is widely used for the desalinization of water used to feed high-pressure steam boilers, as well as in hydrometallurgy and the chemical and pharmaceutical industries.


ion exchange

[′ī‚än iks‚chānj]
(physical chemistry)
A chemical reaction in which mobile hydrated ions of a solid are exchanged, equivalent for equivalent, for ions of like charge in solution; the solid has an open, fishnetlike structure, and the mobile ions neutralize the charged, or potentially charged, groups attached to the solid matrix; the solid matrix is termed the ion exchanger.
References in periodicals archive ?
It can be concluded that a transitional blend layer can improve the strength of surface bonding between the PFSA and PFCA layers and effectively enhance the stability of the resulting ion exchange membrane.
So thin film of ion exchange membrane, because of mechanical and chemical weakness, resulted in unreliability and inapplicability of the membrane to make big commercial and industrial cells, despite the easy ability to produce and setting.
Kim WS, Kim SO, Kim KW (2005) Enhanced electrokinetic extraction of heavy metals from soils assisted by ion exchange membranes.
Linear scalability is a critical consideration when selecting ion exchange membrane chromatography media because it will determine the ease with which a product is transitioned from early-stage clinical production to full-scale commercial manufacture.
A photo of the Pall Mustang Q ion exchange membrane and the Pall Ultipor VF DV50 can be found on www.
Rather than requiring the use of harmful chemicals such as hydrochloric acid or sodium hydroxide, LINX uses ion exchange membrane powered by electricity to remove impurities from water.
Among specific topics are the fundamental science of gas and vapor separation in polymeric membranes, inorganic membranes for pre-combustion carbon dioxide capture, membranes for hydrocarbon processing and separation, ion exchange membranes for vanadium redox flow batteries, and the degradation of polymeric membranes in water and wastewater treatment.
Since both the resin on the ion exchange membranes and within the individual "stacks" is fully exhausted during this operation, it may take 6-12 hours or longer for conductivity to decrease to the pre-sanitization value.