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 .
* H+ (proton ) and OH− (hydroxide ). * Singly charged monatomic ions like Na+ , K+ , and Cl− . * Doubly charged monatomic ions like Ca2+ and Mg2+ . * Polyatomic inorganic ions like SO42− and PO43− . * 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 .
* 1 Applications
* 1.1 Other applications
* 2 Regenerating wasted water * 3 See also * 4 References * 5 External links
A 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.
Industrial and analytical ion-exchange chromatography is another area
to be mentioned.
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 . An important area of the
application is extraction and purification of biologically produced
substances such as proteins (amino acids ) and
Ion-exchange processes are used to separate and purify metals , including separating uranium from plutonium and other actinides , including thorium , and lanthanum , neodymium , ytterbium , samarium , lutetium , from each other and the other lanthanides . There are two series of rare-earth metals , the lanthanides and the actinides, both of whose families all have very similar chemical and physical properties. Using methods developed by Frank Spedding in the 1940s, ion exchange used to be the only practical way to separate them in large quantities, until the advent of solvent extraction techniques that can be scaled up enormously.
A very important case is the
The ion-exchange process is also used to separate other sets of very
similar chemical elements, such as zirconium and hafnium , which is
also very important for the nuclear industry.
Ion-exchange resins in the form of thin membranes are used in chloralkali process , fuel cells and vanadium redox batteries . Large cation/anion ion exchangers used in water purification of boiler feedwater
* 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.
REGENERATING WASTED WATER
Most ion-exchange systems contain containers of ion-exchange resin that are operated on a cyclic basis.
During the filtration process, water flows through the resin
container until the resin is considered exhausted. That happened only
when water leaving the exchanger contains more than the desired
maximal concentration of the ions being removed.
Water softeners are usually regenerated with brine containing 10% sodium chloride . Aside from the soluble chloride salts of divalent cations removed from the softened water, softener regeneration wastewater contains the unused 50 – 70% of the sodium chloride regeneration flushing brine required to reverse ion-exchange resin equilibria. Deionizing resin regeneration with sulfuric acid and sodium hydroxide is approximately 20–40% efficient. Neutralized deionizer regeneration wastewater contains all of the removed ions plus 2.5–5 times their equivalent concentration as sodium sulfate .
* ^ Mischissin, Stephen G. (7 February 2012). "University of
Rochester - Investigation of Steam Turbine Extraction Line Failures"
(PDF). Arlington, VA. pp. 25–26. Archived from the original (PDF) on
23 September 2015. Retrieved 23 February 2015.
* ^ Shkolnikov, Viktor; Bahga, Supreet S.; Santiago, Juan G.
(August 28, 2012). "
* Betz Laboratories (1976). Handbook of Industrial Water
Conditioning (7th Edition). Betz Laboratories.