Organic polymeric cation exchange resins

Ion-exchange polymeric resins are the most important types of exchangers currently in use [113-123], The first, totally organic ion-exchange resin was synthesized in 1935 by Adams and Holmer, when they produced a phenol-formaldehyde cation-exchange resin and an amine-formaldehyde anion-exchange resin, both obtained with the help of condensation polymerization reactions [113], In 1944, D Alelio synthesized styrene-based polymeric resins, which could be modified to obtain both cationic- and anionic-exchange resins. The majority of the resins commercially applied currently are of this type, for example, Amberlite IR-20, Lewatit S-100, Permutit Q, Duolite, C-20, Dowex-50, and Nalcite HCR. 

Weak-acid, cation exchange resins are prepared by copolymerization of an organic acid or add anhydride and a cross-linking agent. As a rule, acrylic or methacrylic acid is used in combination with divinyl benzene, ethylene dimethacrylate, or similar compounds with at least two vinyl groups. The pearl polymerization technique described above can be used if esters instead of the water-soluble acids are polymerized. The esters are hydrolyzed after polymerization. The final products have ionic contents of 9-10 eq/kg (dry). Resins of this type are Amberlite IRC-50, Duolite CS-101, Permutit H-70, and Wofatit CP-300. 

Adsorption of enzymes to various polymeric resins is a straightforward means for immobilization. Zwitterionic molecules such as proteins can bind to both anionic and cationic ion exchange resins. Hydrophobic macroporous resins are also useful for immobilizing many enzymes, particularly lipases. For example, an immobilized form of Candida antarctica lipase B (CAL-B) on acrylic resin has been sold for many years under the name, Novozym 435 (N435). The enzyme is produced in a modified Aspergillus organism by submerged fermentation and is subsequently adsorbed onto a macroporous... 

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