Preparation, Modification And Properties Of Chitosan-silica Composite Aerogels

Chitosan-silica composite aerogels with chitosan and tetraethoxysilane as reaction precursors were successfully prepared by a typical sol-gel method and vacuum freeze drying. Besides, the hydrophobic modification of composite aerogels was carried out by using hexamethyldisilazane as modifier. Morphology, porosity characteristics and adsorption/absorption performances of composite aerogels before and after modification were investigated.Firstly, chitosan-silica composite aerogels were prepared by the sol-gel method. Characterization of chemical composition and morphology of composite aerogels were performed by Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD) and scanning electron microscope(SEM). The results showed that composite aerogels were prepared successfully and had nanoporous structure. Porosity of composite aerogels increased with the increasing of chitosan content, and reached the maximum of 97% when it came to 20 wt%. Besides, adsorption of composite aerogels for heavy metal ion was performed, which indicated that composite aerogel with 40 wt% chitosan content had adsorption capacity of 6 mg/g.Then, hydrophobic chitosan-silica composite aerogels were prepared by a two-step treatment. The morphologies, thermal stability, porosity characteristics, hydrophobicity as well as oil absorbencies of hydrophobic composite aerogels were investigated. The results showed that composite aerogels after hydrophobic treatment exhibited more porous than unmodified samples, and had large pore volumes of almost 1.43 cm3/g. It was also found that composite aerogels with 20 wt% chitosan had compressive strength of 1.38×104 N/m2 and were thermally stable up to nearly 300 °C. Hydrophobicity as well as lipophilicity was demonstrated with water contact angle of 135° and oil contact angle of 0°. Finally, oil absorption and desorption tests indicated that composite aerogel with 20 wt% chitosan had relatively high oil absorbency of 30 g/g and could be reused up to 10 times. Therefore, hydrophobic chitosan-silica composite aerogels in this study have a great potential to be used as efficient and recyclable oil absorbents.