Ultrasound-assisted biodiesel production of blended castor and Karanja oil using nano-magnetic Sr-Fe₃O₄ catalyst:...

Biomass-derived biodiesel has several benefits over fossil-derived diesel. In recent years, the utilization of non-edible oil for biodiesel production has grown significantly. The work presents the process optimization study of biodiesel production via transesterification of non-edible blended oil of castor and Karanja and nano-magnetic Sr-Fe₃O₄ catalyst using the ultrasound process. Nano-catalyst of Sr-Fe₃O₄ was synthesized using the co-precipitation method and characterized by FT-IR, XRD, and SEM & EDX. The RSM-supported Box-Behnken design (BBD) optimization technique is used to optimize the process parameters, i.e. (A) Molar ratio of methanol and oil (6:1-10:1 w/w); (B) Sr-Fe₃O₄ catalyst loading (1.5-2.5 wt.%), and (C) reaction time (10-30 min.). Optimum conditions of molar ratio (8:1), catalyst loading (2.15 wt. %), and reaction time (24 min), at the constant reaction temperature of 60 °C, produced the biodiesel yield of 98%. The activation energy for ultrasound, calculated to be 19.75 kJ/mol, was 1.7 times lower than that of mechanical stirring. Energy studies show that biodiesel produced by an ultrasound system consumes ~95% less energy and has good physicochemical properties compared to the conventional technique. Magnetic recovery of the catalyst shows a significant reduction in post-processing time and process cost.