Non-supercritical drying synthesis and characterization of monolithic alumina aerogel from secondary aluminum dross

In the present study, the pure and monolithic alumina aerogel is synthesized from secondary aluminum dross as a common waste of the aluminum smelting industry. The process includes the extraction of aluminum content of the waste as sodium aluminate liquor through a multi-stage hydrometallurgical treatment, gelation, removal of the salt by-product by washing, three-stage solvent exchange, aging, non-supercritical drying, and calcination. No chemical additives are used to strengthen the gel structure. It is worth mentioning that the drying step of the hydrogel, which has the main effect on the integrity of the aerogel, is performed at ambient pressure and a relatively low temperature (50 °C). The characterization of the obtained alumina aerogel revealed a density of 0.25 g/cm3, a total pore volume of 1.4 cm3/g, a specific surface area of 148.5 m2/g, and a purity of more than 97%.