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Polymeric aminomethylphosphonic acids - 2. polychelatogenes for separation of transition metal ions by membrane filtration

: Riedelsberger, K.; Jaeger, W.; Friedrich, A.


Designed monomers and polymers 3 (2000), No.1, pp.35-53
ISSN: 1385-772X
Journal Article
Fraunhofer IAP ()

Investigations on the complex formation of monomeric and polymeric aminomethylphosphonic acids with several transition metal ions were carried out. These water-soluble complexes were separated from aqueous solution using an ultrafiltration system. The maximal loading capacities of the polymeric chelatogenes with Cu2+, Cd2+, Hg2+, and Pb2+ ions were determined at various pH values. Mixed loading studies were carried out to determine the selectivity of these macromolecular chelating agents for metal ions. Compared with known aminoalkylphosphonic acid groups containing polymers, the polyacryloylaminomethylphosphonic acid in particular exhibits good complexation ability for the transition metal ions Cd2+ and Hg2+. The acid-base equilibria and complexation behavior of these polychelatogenes were investigated. Acid dissociation constants of the chelating agents and the formation constants of the chelates were determined by means of potentiometric titration. Spectrophotometry was used to determine the dependence of the metal ion/ligand ratio of the formed complexes on the pH. The structure of the formed complexes was investigated using IR spectroscopy. Proposals for the structures of the complexes were made on the basis of these measurements.