Structure, composition and water vapor adsorption behavior of silica gels from rice hull

Silica gels prepared from rice hull were found to have properties comparable to two commercial silica gels and a silica gel prepared by the Industrial Technology Development Institute (ITDI) in terms of chemical and amorphous structure, surface area, desiccant characteristics and heats of adsorption. These properties were determined from infrared and x-ray diffraction spectra and from water vapor adsorption measurements. Microstructure comparison by electron microscopy. showed greater uniformity in particle size and distribution for the rice hull silica gels. The acid-treated rice hull gels may have potential as chromatographic material, based on fewer number of elemental impurities detected by x-ray fluorescence, compared to the commercial and ITDI gels. The economic advantage of preparing silica gels (and other silica products) from rice hull could be considerable if the rice hull ash is obtained from properly designed burners using rice hull as a renewable energy source. Aside from production of cheap energy and silica products, the process will contribute to agricultural waste utilization and pollution abatement through reduction of emissions from the current practice of open field burning of rice hull.