Chiang Mai Journal of Science

This work presented a laboratory studies on the preparation of rice husk ash by burning at  700^oC for 3 and 6 h, respectively. Consequently, silica content obtained after heat treatment at 700^oC for 6 h was 98.14%. Rice husk ash (RHA) was purified by alkaline extraction method used 2.0, 2.5 and 3.0 N sodium hydroxide. Percent yield of  silica extracted by 2.5 N. NaOH, was 90.3% and the infrared spectral data supported the presence of hydrogen bonded silinol group and the siloxane groups in silica. Subsequently, the RHAwas subjected to precipitation method in order to produce nanosilica. The precipitation was done by refluxing silica from RHA in boiling 2.0, 2.5 and 3.0 N NaOH, respectively. TEM results showed that 2.5 N NaOH for 10 h provided agglomerate particles with dimension of  5-10. The specificsurface area was found to be 656 m²/g. From X-ray diffractograms and diffraction pattern showed that the obtained products were amorphous nanosilica.