Ion Exchange

Ion exchange is a water treatment process to remove impurities present in the solution. Ion exchange process involves exchange of ions between the insoluble resin and the solution.  Ion exchangers and ion exchange resins containing positively or negatively charged functional groups are used to exchange ions and its removal present in the solution by maintaining electron neutrality (DeSilva, 1999; IAEA, 2002). Hobbs (2009) described ion exchange as a natural process occurring in tissues of plant and animals, soil and minerals.

Heating systems, steam generation and manufacturing processes are affected by the presence of ion concentrations in water particularly cations such as calcium, magnesium, sodium and potassium anions such as sulphate, chloride, nitrate and silica (Demiwater, n.d.; DeSilva, 1999). Ion exchange process assists to remove the cations and anions present in the water solution. Ion exchange process is used for the treatment of radioactive and non-radioactive chemical species in the nuclear industry and chemical industry (IAEA, 2002). Ion exchange can be used in softening, dealkalization, demineralization, nitrate removal, condensate polishing and pollution control (DeSilva, 1999).

Ion exchangers can be strong acidic and basic and weak acidic and basic. Sulpho- and Phospho- acidic groups are strong acidic and strong basic and phenolic and primary amino groups are weak acidic and weak basic (IAEA, 2002).Various forms of inorganic and organic ion exchangers are available with varying properties. Ion exchangers can be naturally occurring and synthetic. Inorganic ion exchangers have greater selectivity and better disposal options than organic resin however organic ion exchangers are reliable and efficient in water coolant systems (IAEA, 2002).

Mineral compounds such as bentonite, Kaolinite and Illite and Zeolites such as analcite, chabazite, sodalite and clinoptilolite are naturally occurring inorganic ion exchangers, polysaccharides such as cellulose, algic acid, straw and peat, proteins such as casein, keratin and collagen and carbonaceous materials such as charcoals, liquites and coals are naturally occurring organic ion exchangers and Zeolites, Titanates and silico-titanates, transition metal hexacyanoferrates are inorganic synthetic ion exchangers (IAEA, 2002).

References

Demiwater (n.d.) Methods of Purification. [Online] Available at http://www.demiwater.nl/ [Accessed on 25 June 2013].

De Silva, F. J. (1999) Essentials of Ion Exchange. [Online] Available at http://www.resintech.com/  [Accessed on 25 June 2013].

Hobbs, D. T. (2009) Ion Exchange and Adsorption Process. [Online] Available at http://www.cresp.org/ [Accessed on 24 June 2013].

International Atomic Energy Agency (IAEA) (2002) Application of Ion Exchange Processes for the Treatment of Radioactive Waste and Management of Spent Ion Exchangers. [Online] Available at http://www-pub.iaea.org/ [Accessed on 25 June 2013].

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