Synthesis and characterization of nanosized-silica gels formed under controlled conditions

Silica gel has been synthesized by the refluxing of rice husk ash with 1 M NaOH and subsequently adjusting the pH using 1 M H2SO4. The high purity of the silica gel has been found to be dependent on: (i) reflux time, (ii) water loading by addition of boiling DI water to the silica gel prior to titration with 1 M H2SO4 and (iii) rinse time on removal of impurities prior to drying. The surface area, pore size and volume of the silica gel were measured; XRD peaks of Na2SO4 impurity were absent after rinsing > 4 times. FTIR spectra showed that all the silica gels made by different schedules had a similar functional composition. The advantages of the present synthesis route are (i) a cost reduction due to the absence of pre-treatment for the rice husks before calcination below 700 °C, and (ii) the formation of a pure high surface area mesoporous amorphous silica gel.