Synthesis of titania–silica aerogel-like microspheres by a water-in-oil emulsion method via ambient pressure drying and their photocatalytic properties

Water-in-oil (W/O) emulsion system of Span 80–Tween 85/n-heptane–n-butanol/titania and silica sols–formamide-1, 2-epoxypropane was manufactured. Wet titania–silica gel microspheres (TSGMs) were synthesized by the sol–gel process in the W/O emulsion system. Formamide as drying control chemical additive was introduced to improve the pore size uniformity of the wet gels, and 1, 2-epoxypropane was employed to reinforce the wet gel structure. Then the obtained TSGMs were dried directly at ambient pressure condition to prepare titania–silica aerogel-like microspheres (TSAMs). The resultant TSAMs were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction and Brunauer–Emmett–Teller method. The results indicate that TSAMs possess similar characters of those aerogels prepared through supercritical fluid drying. The TSAMs have mean diameters of around 100 μm, a bulk density of 0.3 g/cm3, the specific surface area of 415 m2/g and the pore size distribution between 2 and 35 nm with an average pore size of 15 nm. The TSAMs exhibit excellent photocatalytic activity for the degradation of methylene blue which acts as a simulated aqueous organic pollutant in waste water.