Synthesis, Characterization, Swelling, and Metal Uptake Studies of Aryl Cross-Linked Chitosan Hydrogels

Today, many chemical modifications are being made to increase the utilization of chitosan and to make the best use of it. In this study, four novel cross-linked chitosan derivatives in the form of hydrogel (CS-L1 CS-L2, CS-L3, and CS-L4) were prepared by the condensation of chitosan with anisole-based phenolic and nonphenolic aromatic dicarbonyls. Structural analyses were performed by elemental analysis (C, H, N), scanning electron microscopy, Fourier transform infrared, C-13-CP/MAS (cross-polarization, magic angle spinning) nuclear magnetic resonance, powder X-ray diffraction, and thermogravimetric analysis techniques. Metal ion uptake capacities were studied for selected transitionmetal cations in aqueous medium. The amount of metal ions was determined by microwave plasma-atomic emission spectroscopy. In addition, the swelling behaviors were investigated at different temperatures (25 and 37 degrees C) and at different pH values (3, 7, and 10). The order of the selectivity of cross-linked chitosan derivatives toward metal ions was found to be Cu(II) > Cd(II) > Fe(II) > Co(II) > Ni(II). The results showed that the derivatives exhibited the property of hydrogel and suggest that they could be applied in many areas such as metal removing, water removing, and biological applications.