PURIFICATION OF BIODIESEL BY LIGNITE FLY ASH

Abstract

A Lignite fly ash is a solid waste from the electricity plant. It was used as an alternative low-cost adsorbent to purify a crude biodiesel combine with water washing. The raw lignite fly ash was characterized by X-ray fluorescent spectrometry, scanning electron microscopy and surface area analysis. The results showed that the lignite fly ash was composted of SiO2, Al2O3, CaO and Fe2O3 as major components. A crude biodiesel was synthesized from refined palm oil via transesterification with an oil to methanol mole ratio of 1:6 and 1%wt of sodium hydroxide catalyst. Furthermore, the effect of particle sizes, adsorbent dosage and contact time on the adsorption of impurities in biodiesel was investigated. The suitable conditions in the impurities adsorption were using the lignite fly ash of particle size in the range of 150-250 µm, 3%wt adsorbent and 60 min of contact time. The adsorption behavior at equilibrium could be explained by Freundlich isotherm and the adsorption kinetics followed the pseudo-second order kinetic model. The adsorbent could also be used to remove the impurities and methanol in the biodiesel. The lignite fly ash showed an efficiency comparable to the commercial adsorbents including Florisil, activated carbon and silica. Finally, the use of lignite fly ash could eliminate more than 81% of the impurities and reduce 80% of wastewater generated in the system.