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

Silica gel has been synthesized by the refluxing of rice husk ash with 1M NaOH and subsequently adjusting the pH using 1M 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 1M 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 700C, and (ii) the formation of a pure high surface area mesoporous amorphous silica gel.