Chelating resins also known as specific exchangers or chelating sorbents are a subgroup of ion exchange resins.
Chelating resins were developed to obtain higher selectivities of at least one particular counter-ion species. The interaction of a functional group (ligand) of chelating resin and metal (in form of cation or oxoanion) is selective with respect to the nature of the metal. The theory behind the choice of functional group is explained as such: An ion that forms strong complexes with, or is precipitated by, a certain reagent should thus be preferred by a resin into which this reagent has been incorporated.
However, in the case of chelating resins counter ions are bound to resin by coordinate covalent bond or by its combination with electrostatic interactions. While the case of ion exchange, electrostatic force between oppositely charged functional group and ion in solution plays the main role.
Chelating resins have the same bead form and polymer matrix as usual ion exchangers. They are mainly based on crosslinked polystyrene.
Typical functional groups of chelating resins are:
- iminodiacetic acid
- aminophosphonic
- thiourea
- 2-picolylamine