Power of recycling waste cooking oil into biodiesel via green CaO-based eggshells/Ag heterogeneous nanocatalyst

Abstract

The depletion of crude oil sources and a growing understanding of the adverse environmental effects of using fossil fuels promoted the development of alternative techniques to convert waste biomass into biofuels. Considering ecological safety and economic challenges, this work investigates the catalytic transesterification of waste cooking oil (WCO) for biodiesel production as a substitute for fossil fuels. Chicken eggshells were calcined at 900 °C to form CaO nanoparticles (NPs) and impregnated with Ag NPs solution prepared from fresh fenugreek leaf extract. Several characterization methods characterized the catalyst: FTIR, TEM, SEM, XRD, and zeta-potential/particle sizer, confirming the composite's spherical shape and mesoporous structure. The optimal transesterification conditions were achieved by performing batch reaction experiments. The biodiesel product was analyzed, and its fuel features (density and acid number, kinematic viscosity, cloud, and flash points) were determined and compared to standards. Confirmatory techniques (GC-FID, FTIR, 1H NMR, and 13C NMR) were also used to confirm the conversion of WCO into biodiesel. This study revealed the transformation of WCO into biodiesel with acceptable fuel features depending on the CaO/Ag catalyst's effectiveness as an excellent, safe commercial catalyst by its three times reusability with 90% biodiesel yield, ease of recovery, and cheap cost fabrication.