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 ?
In this study, an anion-exchange HPLC method was developed for separation and quantification of PCR products corresponding to the target gene and a reference gene in 30 min and in a single step.
A substantial increase in specific activity was observed after anion-exchange chromatography, when compared to the activity measured after the first affinity chromatographic step.
Phosphorylation of anion-exchange resin was made by three-chloride phosphorus in the presence of waterless chloride aluminium (Turobjonov et al.
The haemoglobin chromatograms eluted from this anion-exchange column were converted with the conventional HPLC cation-exchange chromatography pattern.
Bianco, "Determination of Mono--and Disaccharides in Milk Products by High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection," Anal.
We found the direct immunoassay method to have a test sensitivity within the range reported for anion-exchange methods, and its application and usefulness are similarly dependent on other patient characteristics, in addition to alcohol intake.
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).
Using a combination of gel filtration, anion-exchange chromatography, and reverse-phase high performance liquid chromatography, we isolated an acidic protein which shows a single chain composition, with a molecular mass of ~8 kDa, estimated by SDS-polyacrylamide gel electrophoresis, Its N-terminal sequence has high similarity to disintegrins isolated from different snake venoms, which are known to bind to cellular integrins such as the GPIlb/IIIa fibrinogen receptor on platelets.
Another peak occurs at 500 nm in the in situ notochord and in vitro myotome spectra, but this peak does not shift upon changes in oxygenation state and disappears following anion-exchange chromatographic purification, indicating that it is not a globin-related absorbance (data not shown).
The principal water treatment technique used in the finishing industry is deionisation, a reversible ion-exchange process in which combinations of cation-exchange and anion-exchange resins are used to remove inorganic salts from the feedwater.
The anion-exchange pigments can play two roles: absorbing the harmful chlorides and releasing the inhibiting ions in response.