Synthesis and Characterization of Silica from Ragi Husk Ash (Finger Millet) by a Sol-gel Method

Abstract

Silica aerogel, a mesoporous material, was prepared from ragi husk ash by sol–gel method and dried under atmospheric pressure. In this method, ragi  husk ash, which is rich in silica, was extracted with sodium hydroxide solution to produce a sodium silicate solution. This solution was neutralized with acid to form a silica aerogel. The aged gel was washed carefully by de ionized water and ethanol and finally dried under atmospheric air. A temperature of 700⁰C was found to be optimum ashing temperature with maximum amorphous silica content. From a morphological analysis obtained by SEM and diffraction patterns (XRD), a longitudinal fibrous and amorphous structure was observed for Ragi Husk. FTIR characterization indicated the presence of silanol and siloxane groups. Thermo gravimetric was used to characterize burning behaviour and also to determine the activation energies. This economic technology, as applied to waste material, also provides many benefits to the local agro-industry.

Keywords: Ragi husk Ash, Sol- gel method, Amorphous silica, Aerogel