Improved synthesis of ion-exchange resins through copolymerization of ligand-modified monomers

The pyrazole-containing ligand 2-(3,5-dimethyl-1-pyrazolyl)ethanol (abbreviated NHed) has been coupled with the monomer glycidyl methacrylate. Subsequent copolymerization of this newly synthesized monomer with ethylene glycol dimethacrylate results in ion-exchange resins with a very high conversion of the epoxy groups, i.e. 76% (direct method), far better than the immobilization of NHed onto pre-formed poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (indirect method) which resulted in a conversion of only 6% of the epoxy groups. The newly obtained resins have been tested for their metal-ion binding capacities. Due to the non-chelating character of the immobilized ligand, the metal-ion uptake capacities are rather low. However, an unusual selectivity towards Ni2+ ions in the presence of other divalent transition metal ions was observed. At pH< 2 a very high and consistent Cd2+ uptake is observed under non-competitive and competitive conditions. It is anticipated that this improved polymerization route will not only provide resins with a high ligand concentration, but also with high uptake capacities if ligands with a better complexation ability are used. Copyright (C) 1996 Elsevier Science Ltd.