Adsorption of certain textile dyes onto chitosan. Spectroscopic and thermal analysis

Abstract

The characteristics of products obtained by adsorption of commercial dyes Bezanyl Green F2B (W), Procion Red MX-5B (R), Procion Blue MX-R (D) onto chitosan were investigated by thermogravimetric analysis, FT-IR spectroscopy and polarized optical microscopy. The thermal degradation of pristine chitosan (CH) and chitosan treated with dyes (CH-W, CH-R, CH-D) exhibited two decomposition stages, with a similar shape of the curves. Significant differences between the thermal parameters of the samples occurred during the second decomposition stage, and were correlated with the different structures of the dyes adsorbed onto CH. The thermotropic behaviour of the samples investigated by polarized optical microscopy confirmed the data obtained from TGA.