Distinct complexing trends of chitosan with toxic metals (PO1-24)

Abstract

We have been able to prove that not only adsorption but also complexation of different metals (Pb, Cd, Mo, Cu, Zn and Cr) actually takes place in acetate buffer (pH=4) with Chitosans of different molecular weights and deacetylation degrees. Depending on the different electrochemical behaviour on mercury electrode of studied metals and the nature of the resulting complexes, diverse approaches have been used. Chitosan molecular weight and concentration had been seen to play a key role in the Chitosan binding activity with Zn, Pb and Cd, as reported elsewhere[1]. Length of Chitosan chains influences the degree of complexation with both Cr and Mo, while Cu binding capacity remains independent of the molecular weight of the assayed polymers. The larger the polymer chain length the higher the number of amino group available for the retention of both Cr and Mo within the tridimensional structure of the acting ligand. This is consistent with a predominant intra-chain linkage of both metal atoms. On the contrary, in the case of Cu, an inter-layer binding mechanism is proposed as the main retention factor by Chitosan.