A rapid and low solvent/silylation agent-consumed synthesis, pore structure and property of silica aerogels from dislodged sludge

Dislodged sludge, a kind of industrial waste, was used as raw material to prepare silica aerogels via ambient pressure drying. The effect of solvent exchange and surface silylation on the pore structure and property of the obtained materials was investigated in detail. If the ethanol and n-hexane exchange decreases to 8 h (two times, each time for 4 h) and 4 h (one time), respectively, and the volume ratio of ethanol/wet gel and n-hexane/wet gel reduces to 2 and 1, respectively, the obtained materials exhibit a desirable pore volume of 3.17 cm³/g, a water contact angle of 152.9° and a low thermal conductivity of 0.030 W/ (m·K). Further decreasing the mole ratio of silylation agent/SiO₂ to 0.5 and the silylation time to 6 h results to silica aerogels with a pore volume of 3.44 cm³/g, a water contact angle of 144.5° and a low thermal conductivity of 0.032 W/ (m·K). A rapid synthesis (a total time of 50 h, from wet gel aging to ambient pressure drying) of silica aerogels has been realized and the consumption of solvent/silylation agents has been pronouncedly reduced without sacrificing the thermal insulation property of the obtained materials.