This MedLibrary.org supplementary page on Ion exchange is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion exchangers'.
Typical ion exchangers are ion exchange resins (functionalized porous or gel polymer), zeolites, montmorillonite, clay, and soil humus. Ion exchangers are either cation exchangers that exchange positively charged ions (cations) or anion exchangers that exchange negatively charged ions (anions). There are also amphoteric exchangers that are able to exchange both cations and anions simultaneously. However, the simultaneous exchange of cations and anions can be more efficiently performed in mixed beds that contain a mixture of anion and cation exchange resins, or passing the treated solution through several different ion exchange materials.
Ion exchangers can be unselective or have binding preferences for certain ions or classes of ions, depending on their chemical structure. This can be dependent on the size of the ions, their charge, or their structure. Typical examples of ions that can bind to ion exchangers are:
- H+ (proton) and OH− (hydroxide)
- Single charged monoatomic ions like Na+, K+, or Cl−
- Double charged monoatomic ions like Ca2+ or Mg2+
- Polyatomic inorganic ions like SO42− or PO43−
- Organic bases, usually molecules containing the amino functional group -NR2H+
- Organic acids, often molecules containing -COO− (carboxylic acid) functional groups
- Biomolecules which can be ionized: amino acids, peptides, proteins, etc.
Ion exchange is a reversible process and the ion exchanger can be regenerated or loaded with desirable ions by washing with an excess of these ions.
Contents |
Applications
Most typical example of application is preparation of high purity water for power engineering, electronic and nuclear industries; i.e. polymeric or mineralic insoluble ion exchangers are widely used for water softening, water purification, water decontamination, etc.
Ion exchange is a method widely used in household (laundry detergents and water filters) to produce soft water. This is accomplished by exchanging calcium Ca2+ and magnesium Mg2+ cations against Na+ or H+ cations (see water softening).
Ion exchange chromatography is a chromatographical method that is widely used for chemical analysis and separation of ions. For example, in biochemistry it is widely used to separate charged molecules such as proteins.
Ion exchangers are used to enrich and purify precious metals, including uranium, lutetium, neodymium, samarium, and thallium.
An important area of the application is extraction and purification of biologically produced substances such as amino acids and proteins.
Industrial and analytical ion exchange chromatography is another area to be mentioned.
Ion exchangers are used in nuclear reprocessing and the treatment of radioactive waste.
Ion Exchange is also widely used in the food & beverage, hydrometallurgical, metals finishing, chemical & petrochemical, pharmaceutical, sugar & sweeteners, ground & potable water, nuclear, softening & industrial water, semiconductor, power, and a host of other industries.
Ion exchange resins in the form of thin membranes are used in chloralkali process, fuel cells and vanadium redox batteries.
Others
In soil science, cation exchange capacity is the ion exchange capacity of soil for positively charged ions. Soils can be considered as natural weak cation exchangers.
In planar waveguide manufacturing ion exchange is used to create the guiding layer with higher index of refraction.
References
- F. Helfferich, Ion Exchange, McGraw Hill, New York, 1962 (Bible of the subject).
- Ion Exchangers (K. Dorfner, ed.), Walter de Gruyter, Berlin, 1991.
- Ion exchange (D. Muraviev, V. Gorshkov, A. Warshawsky), M. Dekker, New York, 2000.
- A. A. Zagorodni, Ion Exchange Materials: Properties and Applications, Elsevier, Amsterdam, 2006.
External links
- Illustrated and well defined chemistry lab practical on ion exchange from Dartmouth College
- Some applets illustrating ion exchange processes
- A simple explanation of deionization
- Ion exchange, BioMineWiki
Wikipedia content modification information:
- This page was last modified on 29 July 2008, at 03:41.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Ion exchange".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.