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 ?
Bianco, "Determination of Mono--and Disaccharides in Milk Products by High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection," Anal.
Consequently, many studies demonstrate only effective separation of five arsenic species in food and urine using an anion-exchange column, with AsB eluting at the void volume (8-11).
After SMAS was introduced into the layers of HT by the anion-exchange, the morphology of HT had changed a little during the anion-exchange process and still kept the form of sheets.
Several patient characteristics that affect both diagnostic sensitivity and specificity have mainly been documented for the anion-exchange methods.
The separation was performed using an anion-exchange column (AS 16) with an AG16 guard column.
cation- or anion-exchange surfaces), by use of antibodies immobilized on surfaces, or as described here, by use of simple gold chips or by use of solid-phase extraction before MALDI-TOF-MS.
Analyzing sialic acids using high-performance anion-exchange chromatography with pulsed amperometric detection.
We investigated whether a HPLC assay using an anion-exchange column would be appropriate for plasma mannose determinations.
Most previous work relied on either separation of transferrin isoforms by isoelectric focusing with quantification by immunofixation, staining, and densitometry or separation by anion-exchange chromatography, followed by immunoassay.
The latter can occur as a result of incomplete fractionation of the CDT and non-CDT isoforms by anion-exchange microcolumns (11).