Electrolytic transesterification of waste cooking oil using magnetic Co/Fe-Ca based catalyst derived from waste shells: A promising approach towards sustainable biodiesel production

Biodiesel production is a promising approach to producing renewable liquid fuel and disposing of waste cooking oil (WCO). While the high energy consumption during the conventional thermal transesterification process and the difficulty of reusing the transesterification catalyst are two important factors affecting its development. In this research, biodiesel production by electrolytic transesterification of WCO using reusable magnetic waste shells derived Co/Fe-Ca based catalysts were evaluated. Catalysts were prepared by one-step hydrothermal method. Their properties were characterized by XRD, SEM, XPS, etc, catalytic performances were investigated, and catalytic mechanisms were also explored. Response surface methodology (RSM) based on the Box-Behnken design (BBD) approach was used to optimize the electrolytic transesterification parameters and investigate the interactions of independent parameters. An optimal Fatty acid methyl ester (FAME) content of 92.12% was obtained under a 12:1 methanol to oil molar ratio, 0.25 wt% catalyst dosage, and 29 V electrolytic voltage for 50 min at room temperature. The conversion of WCO is more dependent on electrolytic voltage as compared to the other parameters. And the reaction time has been significantly decreased, energy efficiency was effectively improved compared to conventional thermal catalytic transesterification. Moreover, the WCO biodiesel properties were measured and they all met the ASTM standard. It's hoped that the results of this work could promisingly benefit the sustainable biodiesel production and disposal of WCO.