Effects of Functional Group Density in Stylene-Divinylbenzene Copolymer Phase and of Supporting Electrolyte Concentration in Aqueous Phase on Performance of Iminodiacetate-type Chelating Resin in Terms of Contribution of Ion-Exchange Mechanism.

The effects of the functional group density in the stylene-divinylbenzene copoymer phase and of the supporting electrolyte concentration in the aqueous phase on the perfomance of the iminodiacetate (IDA)-type chelating resin were studied in terms of contribution of an ion-exchange mechanism. High hydrophobicity of the resin having a low functional group density interfered with penetration of aqueous solutions into the resin phase to slow the acid-base reaction and the adsorption reaction. Uptake of the cation in the supporting electrolyte into the resin phase was clearly indicated in each of two acid dissociation reactions. The high concentration of the supporting electrolyte enhanced acid dissociation of the IDA group, and a singly deprotonated species interacting with the supporting electrolyte cation strongly interfered with adsorption by the ion-exchange mechanism, while only slightly interfering with adsorption by the complexation. Both the complexed and ion-exchanged species respectively involving two or more IDA groups were destabilized to reduce the adsorption capacity of the resin having the low functional group density.