Synthesis of TiO2–SiO2 aerogel via ambient pressure drying: effects of sol pre-modification on the microstructure and pore characteristics

TiO2–SiO2 composite aerogels were prepared via ambient pressure drying by sol–gel and surface modification for both the sol and gel samples. The organosilane reagents of decamethyltetrasiloxane (DMTSO)/trimethylchlorosilane (TMCS) and hexamethyldisiloxane (HMDSO)/TMCS were introduced into the TiO2–SiO2 composite sol for pre-modification respectively, and subsequently the TMCS/hexane solution was used for surface modification of the obtained TiO2–SiO2 composite gel. The effects of sol pre-modification on the microstructure and pore characteristics of TiO2–SiO2 composite aerogels were investigated. The results indicate that HMDSO/TMCS coupling reagents is more appropriate for the pre-modification of TiO2–SiO2 composite sol than the DMTSO/TMCS reagents. The best volume ratio of HMDSO/TMCS/composite sol for preparing mesoporous TiO2–SiO2 composite aerogels is in the range of 1:0.33:10–1:1.0:10, with which the specific surface area and pore volume of the obtained TiO2–SiO2 composite aerogels are 492–645 m2/g and 2.63–2.85 m3/g, respectively. The results of adsorption and photocatalytic degradation of rhodamine B show that the as-prepared TiO2–SiO2 composite aerogels have higher adsorption/photocatalysis. Particularly, the as-prepared TiO2–SiO2 composite aerogels with HMDSO/TMCS showed prominent adsorption capability with the adsorption rate attaining to 89.4 % within 60 min.