Study of chitosans interaction with Cu(II) from the corresponding sulfate and chloride salts

Abstract

The interaction of copper ions with chitosan and three synthesized derivatives with different chelating centers, N-benzylidene chitosan, N-benzyl chitosan and poly-N-(4-(4-R-methoxyphenyl) diazenyl)benzyl-chitosan using CuSO4 center dot 5H(2)O and CuCl2 center dot 2H(2)O salts was studied. The content of Cu2+ in the complexes was determined by atomic absorption spectrometry and the results showed that chitosan exhibited higher chelating capacity for both salts. Morphological changes of derivatives and complexes were demonstrated by SEM-EDS. In addition, the presence of some crystals attributed to copper sulfate adsorbed on the polymer surface was also observed, which indicates that part of the metal content is in the salt adsorbed and might influence in the use of the materials for further application studies. This result was supported by Raman spectroscopy results in which vibrations of O= S=O groups were observed. X-ray diffraction patterns showed that the chemical modification of chitosan and formation of complexes resulted in the decrease of crystallinity. Electron paramagnetic resonance was used to investigate structural aspects of the materials complexed with Cu2+ ions in the solid state.