Interaction between chitosan and uranyl ions. Part 2. Mechanism of interaction.

In this part of the study--understanding the mechanism of interaction between chitosan and uranyl ions, we confirmed the restrictive role of polymer crystallinity on uranyl sorption capacity. The saturation of the polymer by uranyl ions showed that approximately 1 mol of uranyl ions was sorbed for 2 mol of amino groups contained in the amorphous domain. This result can be related to the intrinsic properties of chitosan. Desorption experiments are in favour of strong interaction, in fact, no desorption was observed whatever the experimental conditions. Spectroscopic characterization was performed on complexes in solution and in the solid state. U.V.-visible spectrophotometric experiments showed that a unique type of complex was formed. FT-IR spectroscopy allowed us to observe the appearance of a new band at 1525 cm of amide II type and led us to conclude the formation of a unique complex by the coordination with chitosan amino groups.