Synthesis and characterization of superhydrophobic silica and silica/titania aerogels by sol-gel method at ambient pressure

Superhydrophobic SiO2 aerogel and SiO2/TiO2 aerogels were prepared by sol-gel process at ambient pressure drying. The composite aerogels were prepared by keeping the molar ratio of TEOS:TTIP:EtOH:acidic water:basic water constant at 1:1:8:5:0.2 with oxalic acid and NH4OH concentrations fixed at 0.008 M and 0.5 M, respectively. By exchanging with solvents and surface modification, SiO2 aerogel and SiO2/TiO2 composite aerogels with contact angle as high as 152° were prepared. The resultant aerogels were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM) and Brunauer-Emmett-Teller method (BET). The results indicate that the aerogels have three-dimensional nanoporous structure and the specific surface areas of SiO2 aerogel and SiO2/TiO2 composite aerogels are 765 m2/g and 735 m2/g, respectively. In order to evaluate the photocatalytic activity of SiO2/TiO2 composite aerogels, the decomposition of Rhodamine B was used as probe reaction. The results revealed that SiO2/TiO2 composite aerogels exhibited high photocatalytic activity and was easier to recycle from a solution suggesting a potential application in waste-water treatment.