Complexation properties of natural and synthetic polymers of environmental and biological interest in presence of copper(II) at neutral pH

• Type: Article in International Scientific Journal
• Date: 1997

Authors

Vasconcelos, MTSD (Author) Other; Gomes, CAR (Author) FCUP

Journal

Title: European Polymer Journal

Vol. 33

Pages: 631-639

ISSN: 0014-3057

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 19 Citations

Scopus - 24 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-001-BG6

Abstract (EN): Scatchard and differential equilibrium function (DEF) models were applied in parallel (for comparison) to potentiometric titration data (25 degrees C, pH 6.5 and ionic strength 0.1 mol l(-1)) of natural or synthetic polymers: starch, cellulose, amylopectin, chitin, Chelex-100, Chelamine and Bio-Rex-70, and humic acids (the last for comparison). Copper(II) was used as titrant. To demonstrate exactly the meaning and quality of the results, identical studies were carried out on: (i) real and well known systems with simple ligands (succinate and proline); and (ii) simulated systems including ligands with one, two, three or 10 different types of coordination sites (simulated titration curves). The aim of the work was the determination of: (a) conditional stability constants of copper complexes; and (b) copper(II) complexation capacity of the polymers. The relative affinity for copper(II) of the different polymers (given by the differential equilibrium function, K-DEF), decreased in the following order at pH 6.5: Chelamine > Chelex-100 similar or equal to humic acids > Bio-Rex-70 similar or equal to cellulose > amylopectin similar or equal to chitin greater than or equal to starch. In the range of copper(II)to-polymer concentrations embraced, the binding strength of the Chelex-100 was ca one order of magnitude lower than that of Chelamine, and similar to that found for the humic acids. The complexation capacity of the polymers decreased in the following order: Bio-Rex-70 > Chelex-100 > Chelamine, chitin much greater than starch > cellulose > amylopectin. All polymers, including the synthetic resins whose sorption sites are chemically homogeneous, behaved as heterogeneous ligands, like humic acids (i.e. the magnitude of the microscopic stability constants decreased when the fraction of all sites occupied by metal ions increased) probably due to both electrostatic and steric effects, and limitations of the methods of analysis and calculation.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9