Thesis (M.Sc.)--Chulalongkorn University, 2008

This research developed a high grade silica adsorbent from rice husk ash. It was extracted by sodium hydroxide solution and formed gel by adjustment pH with sulfuric acid. Effect of aging silica gel at pH 1, 3, 7 and 9 were investigated and characterized. Aging silica gel at pH 3 gave the highest yield, 85.19% of product. Results from nitrogen adsorption indicated that all synthesized adsorbents were mesoporous. Synthesized silica at aging pH 1 presented the highest specific surface area of 662.68 m[superscript 2]/g. Data from X-ray fluorescent showed that synthesized silica at aging pH 1 gave the highest purity of silica of 99.96%. X-ray diffraction technique confirmed that all synthesized silica gel were amorphous form. Results from infrared spectroscopy showed a little different at wavelength 951 cm[superscript -1]. Then silica products were controlled particle size and tested efficiency of separation of compounds using 2 techniques of chromatography namely column chromatography and thin-layer chromatography. Synthesized silica at aging pH 1 showed the best results for efficiency of separation and gave the highest resolution of 1.69 when tested with column technique. When compared with commercial adsorbents, it was found that silica product had efficiency of separation close to commercial adsorbents.