SORPTION OF DIVALENT METAL-IONS ON AN IMINODIACETIC RESIN FROM ARTIFICIAL SEAWATER

The sorption of some bivalent metal ions on the iminodiacetic resin Ch elex 100 was examined in artificial seawater as an example of a comple x matrix, and in the presence of an organic chelating substance in the aqueous phase. The curves reporting the fraction of sorbed metal ions in function of the solution pH were determined experimentally under d ifferent conditions and the exchange coefficients were calculated. The intrinsic complexation constants, which are independent of the condit ions, were evaluated on the basis of the Gibbs-Donnan model for the re sin and agree with those previously obtained in the case of the sorpti on of the same metals on Chelex 100 from solutions of simpler composit ion. In some instances the intrinsic complexation constants were simil ar to the corresponding complexation constants in aqueous solution, wh ile in other cases they were different, depending an the activity coef ficient ratio of the species inside the resin. It has been demonstrate d that the method derived from the Gibbs-Donnan model can be used for describing and predicting the sorption equilibria also from complex so lutions, if all the equilibria set up in the considered system are kno wn.