Preparation of silica aerogel from rice hull ash by drying at atmospheric pressure

The silica aerogel was prepared by a sol-gel process followed the drying process at atmospheric pressure and 40 °C. The silicon source was the rice hull ash, which is an agricultural waste and rich in silicon. The rice hull ash was extracted with sodium hydroxide solution to get a sodium silicate solution. The solution was neutralized with sulfuric acid solution to form silica hydrosol, which was immediately added appropriate quantity of tetraethyl orthosilicate (TEOS), and then gelated to be a gel. The aged gel was washed successively by water and ethanol, and finally dried at the atmosphere. The prepared material was characterized using transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) measurements. The specific surface area of the prepared material is high as 500 m²/g with a bulk density of 0.33 g/cm³. The diameters of the pores inside the prepared materials are between 5 and 60 nm.