Ion exchange 1

Ion exchange

Ion exchanger

Ion exchange resin beads

Ion exchange column, used for protein purification

Ion exchange is an exchange of ionsbetween two electrolytes or between anelectrolyte solution and a complex. In mostcases the term is used to denote theprocesses of purification, separation, anddecontamination of aqueous and otherion-containing solutions with solidpolymeric or mineralic 'ion exchangers'.

Typical ion exchangers are ion exchangeresins (functionalized porous or gelpolymer), zeolites, montmorillonite, clay,and soil humus. Ion exchangers are eithercation exchangers that exchange positivelycharged ions (cations) or anion exchangersthat exchange negatively charged ions(anions). There are also amphotericexchangers that are able to exchange bothcations and anions simultaneously.However, the simultaneous exchange ofcations and anions can be more efficientlyperformed in mixed beds that contain amixture of anion and cation exchange resins,or passing the treated solution throughseveral different ion exchange materials.

Ion exchangers can be unselective or havebinding preferences for certain ions orclasses of ions, depending on their chemicalstructure. This can be dependent on the sizeof the ions, their charge, or their structure.Typical examples of ions that can bind toion exchangers are:

• H+ (proton) and OH− (hydroxide)• Single-charged monatomic ions like Na+,

K+, and Cl−

• Double-charged monatomic ions likeCa2+ and Mg2+

• Polyatomic inorganic ions like SO42− and PO4

3−

• Organic bases, usually molecules containing the amine functional group -NR2H+

• Organic acids, often molecules containing -COO− (carboxylic acid) functional groups• Biomolecules that can be ionized: amino acids, peptides, proteins, etc.Along with absorption and adsorption, ion exchange is a form of sorption.

Ion exchange 2

Ion exchange is a reversible process and the ion exchanger can be regenerated or loaded with desirable ions bywashing with an excess of these ions.

ApplicationsIon exchange is 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.Most typical example of application is preparation of high purity water for power engineering, electronic and nuclearindustries; i.e. polymeric or mineralic insoluble ion exchangers are widely used for water softening, waterpurification, water decontamination, etc.Ion exchange is a method widely used in household (laundry detergents and water filters) to produce soft water. Thisis accomplished by exchanging calcium Ca2+ and magnesium Mg2+ cations against Na+ or H+ cations (see watersoftening). Another application for ion exchange in domestic water treatment is the removal of nitrate and naturalorganic matter.Industrial and analytical ion exchange chromatography is another area to be mentioned. Ion exchangechromatography is a chromatographical method that is widely used for chemical analysis and separation of ions. Forexample, in biochemistry it is widely used to separate charged molecules such as proteins. An important area of theapplication is extraction and purification of biologically produced substances such as proteins (amino acids) andDNA/RNA.Ion-exchange processes are used to separate and purify metals, including separating uranium from plutonium andother actinides, including thorium, and lanthanum, neodymium, ytterbium, samarium, lutetium, from each other andthe other lanthanides. There are two series of rare earth metals, the lanthanides and the actinides, both of whosefamilies all have very similar chemical and physical properties. Using methods developed by Frank Spedding in the1940s, ion-exchange used to be the only practical way to separate them in large quantities, until the advent of solventextraction techniques that can be scaled up enormously.A very important case is the PUREX process (plutonium-uranium extraction process), which is used to separate theplutonium and the uranium from the spent fuel products from a nuclear reactor, and to be able to dispose of the wasteproducts. Then, the plutonium and uranium are available for making nuclear-energy materials, such as new reactorfuel and nuclear weapons.The ion-exchange process is also used to separate other sets of very similar chemical elements, such as zirconiumand hafnium, which is also very important for the nuclear industry. Zirconium is practically transparent to freeneutrons, used in building reactors, but hafnium is a very strong absorber of neutrons, used in reactor control rods.Ion exchangers are used in nuclear reprocessing and the treatment of radioactive waste.Ion exchange resins in the form of thin membranes are used in chloralkali process, fuel cells and vanadium redoxbatteries. Ion exchange can also be used to remove hardness from water by exchanging calcium and magnesium ionsfor sodium ions in an ion exchange column.Liquid (aqueous) phase ion exchange desalination has been demonstrated.[1] In this technique anions and cations insalt water are exchanged for carbonate anions and calcium cations respectively using electrophoresis. Calcium andcarbonate ions then react to form calcium carbonate, which then precipitates leaving behind fresh water. Thedesalination occurs at ambient temperature and pressure and requires no membranes or solid ion exchangers.Theoretical energy efficiency of this method is on par with electrodialysis and reverse osmosis.

Ion exchange 3

Other applications• 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 pollution remediation and geotechnical engineering, ion exchange capacity determines the swelling capacity of

swelling or Expansive clay such as Montmorillonite, which can be used to "capture" pollutants and charged ions.• In planar waveguide manufacturing, ion exchange is used to create the guiding layer of higher index of refraction.• Dealkalization, removal of alkali ions from a glass surface.• Chemically strengthened glass, produced by exchanging K+ for Na+ in soda glass surfaces using KNO3 melts.

References[1] http:/ / microfluidics. stanford. edu/ Publications/ ITP/

Shkolnikov%202012%20Desalination%20and%20hydrogen,%20chlorine,%20and%20sodium%20hydroxide%20production%20via%20electrophoretic%20ion%20exchange%20and%20precipitation.pdf

•• F. Helfferich, Ion Exchange, McGraw Hill, New York, 1962 (Bible of the subject).•• Ion Exchangers (K. Dorfner, ed.), Walter de Gruyter, Berlin, 1991.•• C. E. Harland, Ion exchange: Theory and Practice, The Royal Society of Chemistry, Cambridge, 1994.•• 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. (http:/ /

www. ionexchange. books. kth. se)

External links• Illustrated and well defined chemistry lab practical on ion exchange from Dartmouth College (http:/ / www.

dartmouth. edu/ ~chemlab/ chem3-5/ ionx1/ overview/ start. html)• Some applets illustrating ion exchange processes (http:/ / www. ionexchange. books. kth. se/ applets. html)• A simple explanation of deionization (http:/ / www. veoliawaterst. com/ en/ files/ ?file=960)• Ion exchange, BioMineWiki (http:/ / wiki. biomine. skelleftea. se/ wiki/ index. php/ Ion_exchange)

Article Sources and Contributors 4

Article Sources and ContributorsIon exchange  Source: http://en.wikipedia.org/w/index.php?oldid=604347367  Contributors: APerson, Afluegel, Anna.h.bauer, Armando-Martin, Artifactblue, BeefRendang, Beetstra, Bioc0,Bob, Brackenheim, Cacycle, Chongkian, Christian75, Daniele Pugliesi, Drphilharmonic, Femto, Gproud, Hagecius, Hermann Luyken, Heron, Hirohisat, Hroakes, Hu, Itub, Jeffreygsinger,Lamiot, Landlord77, Malangthon, Mets501, MiPe, Mild Bill Hiccup, Mion, Mitartep, Mmarre, Mnmngb, Mysid, Nixopax, Polly, Polyamorph, RHaworth, Raysonho, RekishiEJ, Rifleman 82,Riventree, RuED, Samuel Grant, SchreiberBike, Singhalawap, SkyMachine, Sohmc, Spike Wilbury, Stone, Svdmolen, TimBentley, Tomchurch100, V8rik, Vasily.Kravtsov, Vieque, Y2000, 62anonymous edits

Image Sources, Licenses and ContributorsFile:Ionenaustauscher.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ionenaustauscher.jpg  License: Creative Commons Attribution 3.0  Contributors: Robin MüllerFile:Ion exchange resin beads.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ion_exchange_resin_beads.jpg  License: Public Domain  Contributors: Original uploader was Bugmanat en.wikipediaImage:Ion exchange column.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ion_exchange_column.jpg  License: Public Domain  Contributors: TimVickers

LicenseCreative Commons Attribution-Share Alike 3.0//creativecommons.org/licenses/by-sa/3.0/