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 ?
Sharma, "Acetalization of Ethylene Glycol with Formaldehyde using Cation-Exchange Resins as Catalysts: Batch Versus Reactive Distillation," React.
Cation-exchange properties of hydrothermally treated coal fly ash // Envir.
2009 Capillary electrophoresis 7% Cation-exchange HPLC 93% Note: Table make from pie chart.
The resulting ash was prepared for strontium analysis using the same process of acid-dissolution, cation-exchange, and filament loading used for the bulk soil samples, including the HF and HN[O.
We performed cation-exchange HPLC (PolyCAT A column) according to (21) and RP HPLC as described in (22).
6] for several hours in an electric furnace at high temperature, exhibits a cation-exchange capacity of 100 meq/100g.
Barticevic E, Gonzalez S, Aomine S (1975) Cation-exchange capacity of the sand fraction of some Chilean soils.
HbA1, consisting of HbA1a, HbA1b, and HbA1c, received its name because of its fast-eluting nature as quantified with cation-exchange chromatographic methods.
Oasis weak cation exchange cartridges (Waters) contain mixed-mode weak carbonyl cation-exchange material, which retains strong bases such as MNs, at pH >5, permitting the cartridge to be washed thoroughly with both water and 100% acetonitrile without elution of the analytes of interest.
Dielectric permittivity and conductance of systems of the type: electrolyte-membrane-electrolyte for several cation-exchange and anion-exchange membranes in the frequency range 1-80 MHz were reported by Spiegler (4).
Cation-exchange capacities and mineralogy of the fine-sand separates (0.
Ideally, pH, ([SIGMA]Exi), or CEC should be constant across the entire isotherm to generate cation-exchange isotherm or estimate the cation selectivity coefficients.