Chelating Resins

Chelating resin is classified as one type of ion exchange resins, which is generally composed of polymer matrix and chelating group. The polymer matrix...
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Chelating Resins

Chelating resin is classified as one type of ion exchange resins, which is generally composed of polymer matrix and chelating group. The polymer matrix includes synthetic organic polymers and natural organic polymers, which are insoluble but swollen in water and a variety of organic solvents. Chelating groups usually containing nitrogen (N), oxygen (O), and/or sulfur (S) donor atoms are immobilized on the polymer matrix.

The retention of metals by cation exchange resins occurs through the exchange, by the ionogenic groups, of loosely bound hydrogen (H) or sodium (Na) ions (counterions) for the metal ions. Chelating resins work differently from ion exchange resins by the formation of strong complexes with the selected ions through the chelating groups. Regeneration of chelating resins can be achieved by disrupting the formation of the complex or by using competing ligands that are more favorable than the resin functional groups.

Iminodiacetic acid (IDA) that can form complexes (chelate) with various elements is the most popular chelating group. Similar to IDA, aminomethyl phosphonic acid (AMPA) as a chelating group is also employed in N and/or O coordination. The AMPA-type chelating resin is effective for extraction of Indium (In), rare earth elements (REEs), uranium (U), and thorium (Th). Chelating groups containing S donor atom, such as thiol, thiourea, and thiouronium, are widely used for chelating resins and have high affinity for elemental silver (Ag), mercury (Hg), copper (Cu), and plumbum (Pb).

Chelating resins are widely used for metals removal, recovery, and enrichment. Use of chelating resins can simplify fractionation of heavy metal toxicity.