Thesis (M.Sc.)--Chulalongkorn University, 2012

A natural low silica bentonite (LSB) was used as adsorbent for purifying biodiesel. The concentrations of sulfuric acid, activating time, particle size and amount of adsorbent parameters to activate LSB were studied. The most efficient of LSB for purifying crude biodiesel was obtained by activating LSB with 0.25 M H2SO4 in DI water at 100 0C for 1 hour. By using 5% of activated LSB with 60-80 mesh size, 57.22% of soap could be removed and the adsorption isotherm was fit with Freundlich isotherm. The surface area, chemical composition and structure were characterized by BET, XRF and FTIR techniques, respectively. The specific surface area could be improved from 25.398 to 48.928 m2 g−1 by acid treatment. An exchange of Al3+, Fe3+ and Mg2+ with H+ ions leading to a modification of composition in the octahedral sheets was exhibited by XRF. Moreover, intensity of Al–Al–OH band at 915 cm-1 was decreased after acid activation. Acid activated LSB was showed to be an efficacious adsorbent for purifying biodiesel.