Characterization of sorption equilibria of nickel(II) on complexing resins by the Gibbs-Donnan model.

In the present work the sorption of nickel(II) on two cationic resins containing different complexing groups, Chelex 100 and Amberlite CG-50, was studied on the basis of Gibbs-Donnan model. The composition of the complexes formed inside the resin is determined, together with the respective intrinsic complexation constants. These quantities, even though non-thermodynamic, are independent of the composition of the aqueous phase and can be used for the prediction of the exchange coefficients in particular conditions. Nickel(II) is strongly sorbed by Chelex 100 through formation of two different complexes in the resin, NiL and NiL2, (L indicates the donor group), depending on the conditions of the solution phase. It is less strongly sorbed by Amberlite CG-50, where only NiL was detected. This agrees with the nature of the active groups present in the two resins: i. e. the iminodiacetic one and carboxylic one respectively.