Binding of Heavy Metals to Polymeric Ligands; An Electrochemical Study

Abstract

A number of naturally occurring metal complexing agents is polyelectrolytic, i.e. they may be considered as macromolecules with many ligand sites per molecule. It is known that the interaction between charged polymers and their counterions is largely controlled by non-specific, electrostatic effects which result from the field around the polyion. We found it worthwhile to compare the binding of heavy metal ions to natural humic acids with the characteristic binding of cations to synthetic polyacids. Such a study would seem to be especially helpful in answering the question whether the frequently observed dispersion of effective stability constants for metal/humic acid complexes is (only) caused by a distribution of chemical affinities of the different binding sites [see e.g. Buffle (1983) and Shuman et al (1983)].