ion exchange

(redirected from Anion exchange membrane)
Also found in: Dictionary, Thesaurus, Medical.

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 ?
The concentrations of exudates measured from root tips and mature regions indicate that poor absorption of organic anions onto anion exchange membranes was not a constraint to collection, as the elution efficiency of these membranes (as measured by malate) is greatest at low anion concentrations.
The data presented from the controlled environment experiment demonstrate the application of anion exchange membranes for non-destructive collection of organic anions from discrete regions of soil-grown plants (Fig.
Using anion exchange membranes, a selection of organic anions was detected on the root tips and mature regions of nodal roots from plants grown in the controlled environment.
Relationship of turfgrass growth and quality to soil nitrate desorbed from anion exchange membranes.
Turfgrass reflectance measurements, chlorophyll, and soil nitrate desorbed from anion exchange membranes.
Anion exchange membranes were used to relate relative DMY and quality of turfgrass to desorbed soil N[O.
Parameters for quadratic response plateau (QRP) and Cate-Nelson (C-N) models relating relative dry matter yield to desorbed nitrate from anion exchange membranes.