ion exchange

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Related to Cation exchanger: Cation exchange resin, Anion exchanger

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
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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The EDX and ICP analysis of sample S4 that represented the most proper cation exchanger prepared sample investigated its chemical composition and were tabulated in Table 2.
Keywords: Chromium (III) hybrid cation exchangers ion exchange kinetics spent tanning bath thermodynamics.
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Electrical conducting behavior was an additional advantage of such materials; thus, electrically conducting composite cation exchangers were developed as new class of advance materials (8-10).
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