A chitosan-assisted co-assembly synthetic route to low-shrinkage Al2O3-SiO2 aerogel via ambient pressure drying

A straightforward chitosan/inorganic salts co-assembly sol-gel strategy was explored to modify the alumina gel at a molecular level, based on polymerization and covalent interaction of chitosan polysaccharide. Serving as a 3D soft template, the chitosan could chelate with hydrolyzed aluminum species to form an enhanced interdigitated network. A monolithic chitosan/alumina-silica (CAS) composite aerogel with fairly low shrinkage of about 17% was contrived through a follow-up surface modification by tetraethoxysilane and a simple ambient pressure drying (APD) process. It was found that the morphology and nanostructure of the aerogel could be readily tuned by changing the amount of acetic acid during the sol-gel process. Compared with the conventional alumina-silica aerogel, CAS aerogel exhibited analogous high temperature thermal stability and refined microstructure, making it as a favorable candidate in adsorption and catalysis arenas at higher temperature. Moreover, the monolithic CAS composite aerogel is expected to be beneficial in modifying membranes for baromembrane separation due to its high porosity as well as hydrophilic property.