The preparation and characterization of chitosan rods modified with Fe3+ by a chelation mechanism

Chitosan composite rods (CS-Fe3+) were prepared via an in situ precipitation method. The relationships among the preparation, structures, and properties of the CS-Fe3+ composite rods have been investigated. The results of Fourier-transform infrared spectroscopy (FTIR) and core electron X-ray photoelectron spectroscopy (XPS) indicate that the CS and Fe3+ are coordinated via a chelation mechanism. The content of Fe3+ in the complex was determined by atomic absorption spectrometry (AAS) and elemental analysis (EA), the results of which suggested that the content of Fe3+ in the complex can be controlled by the concentration of the ferric salts during coordination. The changes in thermal stability and crystallization properties were measured by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) patterns, respectively. Scanning electron microscopy (SEM) was used to observe the morphological change of the CS-Fe3+ complex rod. After coordination with Fe3+, the CS rod had a denser, layered structure. However, the layered structure cannot remain intact when the ratios of -NH2/Fe3+ are 100/15 and 100/20. Moreover, its thermal stability decreased, and its bending strength was improved significantly (from 86 MPa to more than 210 MPa), despite the remarkable decrease in the degree of crystallinity.