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.

K. V. CHMUTOV

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 ?
A combination of anion-exchange and cation-exchange chromatography (HPLC) provides good separation of the arsenic species, and ICPMS provides sensitive and specific detection of arsenic.
Of 85 specimens with PBG <0.5 by LC-MS/MS, 8 (9.4%) had values >2.0 mg/24 h by the quantitative anion-exchange method (mean [+ or -] SD, 4.3 [+ or -] 1.8 mg/24 h).
Thus, genetic Tf variants cannot be detected by anion-exchange chromatography followed by immunoassay (a procedure usually used by commercial CDT tests).
When sera (n = 14) from PCa patients with PSA concentrations of 20-700 [micro]g/L were fractionated by anion-exchange chromatography, endogenous PSA-API showed the same chromatographic behavior as that formed in vitro (Figs.
In short, after in vitro iron saturation of transferrin (mixing 50 [micro]L of serum sample, 200 [micro]L of ferric citrate solution, and 1 mL of buffer) and adsorption of isotransferrins with isoelectric point values <5.7 (non-CDT-isotransferrins) on the anion-exchange microcolumns, the isotransferrins with isoelectric point >5.7 (CDT-isotransferrins) in the column effluxes were determined by means of a competitive, double-antibody immunoadsorbent assay.
The incubated sample was then injected into the anion-exchange column (MonoQ 16/10, Pharmacia) for the separation.
Since appropriate anion-exchange columns are available, the use of microbore HPLC should be preferred for the realization of lower detection limits-desirable, for example, for the detection of asialotransferrin in nasal fluid if cerebrospinal fluid leakage is suspected [17,18].
High-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) of D-mannose in serum samples.
Having transfection grade plasmid DNA available is critical to today's high value biopharmaceutical applications and working with Macherey-Nagel's proven anion-exchange technology will allow to develop a cost effective automation solution for this important process, added Piero Zucchelli, CEO and co-founder of Andrew Alliance.
In the present case, the mean free energy values for chromate adsorption by AC range from 8.63 - 11.04 kJ mol-1 which strongly supports that anion-exchange mechanism is involved in removing chromate anion from aqueous solution through AC.