Effect of Rhombohedral and Spherical BiFeO3 Catalyst on Biodiesel Production from Waste Cooking Oil

The present investigation deals with the transesterification of waste cooking oil (WCO) in the presence of bismuth ferrite (BiFeO3) with different morphologies (rhombohedral and spherical) as catalysts for biodiesel production. The rhombohedral BFO was synthesised via biotemplated sol-gel technique in the presence of carrageenan, whereas the spherical was synthesised using the hydrothermal method. The average particle sizes of the rhombohedral and spherical BiFeO3 were found to be 88 nm and 15 mu m, respectively. In addition, the crystallite sizes of the rhombohedral (19.39 nm) were smaller than the spherical (71.83 nm) catalyst. The WCO applied in this study contained a high amount of palmitoleic acid, palmitic acid and stearic acid to be converted into their methyl esters in the presence of both catalysts. The best condition for a maximum yield of fatty acid methyl esters (FAME) using the rhombohedral BiFeO3 as catalyst was 1:6 oil to methanol molar ratio, 0.02 g mass of catalyst, 80 degrees C reaction temperature and one hour of reaction time while for spherical sample, it required a 0.03 g catalyst mass, reaction temperature of 110 degrees C within 3 h with 1:12 oil to methanol molar ratio. The rhombohedral catalyst showed better performance than the spherical catalyst in producing maximum methyl esters with low temperatures and a short time.