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Ion-exchange resin beads. An ion-exchange resin or ion-exchange polymer is a resin or polymer that acts as a medium for ion exchange, that is also known as an ionex. [1] It is an insoluble matrix (or support structure) normally in the form of small (0.25–1.43 mm radius) microbeads, usually white or yellowish, fabricated from an organic polymer substrate.
Ion-exchange resins in the form of thin membranes are also used in chloralkali process, fuel cells, and vanadium redox batteries. Idealised image of water-softening process, involving exchange of calcium ions in water with sodium ions from a cation-exchange resin on an equivalent basis.
Examples of functional groups of Weak ion exchange resins include diethylaminoethyl (DEAE, -C 2 H 4 N(C 2 H 5) 2), which is an anion exchanger, and carboxymethyl (CM, -CH 2-COOH), [35] which is a cation exchanger. These two types of exchangers can maintain the charge density of their columns over a pH range of 5–9.
The resin is a weak exchanger because it is only partially ionized over most pH values, and an efficient separation with DEAE-C chromatography requires a specific, narrow pH range. [ 8 ] Cellulose, dextran, agarose, and other insoluble complexes are unaffected because they compose inert matrices, hence why they are so often derivatized with ...
Chelating resins have the same bead form and polymer matrix as usual ion exchangers. Their main use is for pre-concentration of metal ions in a dilute solution. Chelating ion-exchange resins are used for brine decalcification in the chlor-alkali industry, the removal of boron from potable water, and the recovery of precious metals in solutions.
The resin has a higher affinity for highly charged countercations, for example by Ca 2+ (calcium) in the case of water softening. Correspondingly, anion-exchange resins are typically provided in the form of chloride Cl −, which is a highly mobile counteranion. Counterions are used in phase-transfer catalysis.
An ion-exchange membrane is generally made of organic or inorganic polymer with charged (ionic) side groups, such as ion-exchange resins. Anion-exchange membranes contain fixed cationic groups with predominantly mobile anions; because anions are the majority species, most of the conductivity is due to anion transport. The reverse holds for ...
In the case of a water softener, the cation exchange resin is exchanging sodium (the Na + ion of NaCl) for hardness minerals such as calcium and magnesium. A dealkalizer contains strong base anion exchange resin that exchanges chloride (the Cl – ion of the NaCl) for carbonate (CO − 3), bicarbonate (H C O − 3) and sulfate (SO 2− 4). As ...