Ion exchange resins are polymers in the form of small gel spheres that are capable of exchanging particular ions (cations or anions) within the polymer with ions in a solution that is passed through them. Synthetic resins are mainly used to purify water, but also for various other applications, including the separation of some elements.
Gel bead (polymer) resins are usually sulfonic or carboxylic acid or quaternary ammonium salts. These polymers contain acid groups are classified as acid or cation exchangers, when they exchange positive ions, such as hydrogen ions and metal ions; ammonium groups are considered base or anion exchangers because they exchange negative ions, ordinary hydroxide ions or halide ions.
Ion exchange resin types are lightweight, porous solids, often processed into granules, beads or sheets. When immersed in a solution, the bead absorbs the solution and swells; the level of swelling depends on the structure of the polymer and the total concentration of ions in the solution.
Suitable chemical composition and physical properties can be synthesized at will for specific ion exchange applications; therefore, they form the synthetic ion exchange materials used in laboratories and industry.
In industrial and domestic applications, ion exchange resins are used to remove calcium, magnesium, iron and manganese (water softening), demineralization, to retain concentrations of valuable elements such as gold, silver and uranium from ores.
In chemical analysis, ion exchange resins are used to separate or concentrate ions in chemical synthesis, some ion exchange resins are used as effective catalysts, especially in sterilization and hydrolysis reactions.
There are two different types of polymers that are usually classified as ion exchange resins, although their functions are not related to ion exchange. These are chelating and electronic types of exchange resins.
The chelating polymer type
These are styrene-divinylbenzene polymers that iminodiacetate groups are introduced. This functional group is complexed with all metallic elements, except alkali metals, with different stability with different metals; In chemical analysis, they are used to separate metal fingerprints.
Electron exchange polymer type
They provide electrons in the surrounding solution and are used in oxidative reactions; Examples are polymers prepared from hydroquinone, phenol and formaldehyde.