Ion exchange resin is a kind of macromolecular compound with a network structure and functional groups.
Due to the different properties of the radical exchange groups, ion exchange resins can be divided into two categories: resins that exchange with cations in the solution are called cation exchange resins; resins that exchange with anions in the solution are called anion exchange resins.
Cation exchange resin contains weakly acidic groups, such as carboxyl (-COOH), which dissociate H+ in water and become acidic. When the resin dissociates, the remaining negatively charged groups (such as R-COO-) can adsorb and bind with other cations in the solution, thereby producing a cation exchange effect. The acidity, i.e., dissociation, of this resin is weak, and it is difficult to dissociate and exchange ions at low pH, and it can only be effective under alkaline, neutral or slightly acidic conditions.
Cation exchange resin contains a large number of acidic groups, which decompose hydrogen ions in water and exchange with cations. This once again emphasizes the importance of the chemically active groups of cation exchange resins to the cation exchange process.
Like low molecular weight acids and bases, ion exchange resins can be divided into strong acid cation resins and weak acid cation resins according to their different degrees of ionization.