SORPTION OF METAL-IONS ON A WEAK ACID CATION-EXCHANGE RESIN CONTAINING CARBOXYLIC GROUPS

The sorption properties of a commercial resin containing a carboxylic active group, Amberlite(R) CG-50, for magnesium, calcium, copper and z inc were investigated on the basis of the Donnan model. It is assumed that the main driving force for the sorption of divalent metal ions is the complexation by the carboxylic groups inside the resin. Under typ ical batch conditions (large excess of ligand) only the 1:2 complexes are formed for all metal ions considered, whereas in aqueous solution only 1:1 complexes are reported for calcium and magnesium and the mono meric analogues of the active group of Amberlite(R) CG-50. The intrins ic complexation constants obtained from the batch experiments agree we ll with those in aqueous solution. The same holds for the intrinsic co mplexation constant evaluated from chromatographic experiments. This c onfirms some previous results obtained with a chelating resin containi ng an iminodiacetic group, Chelex 100. The values of the complexation constants for the carboxylic groups found with Chelex 100 are in agree ment with those found with Amberlite(R) CG-50.