Sustainable biodiesel production from waste cooking oil using banana peel biochar-Fe2O3/Fe2K6O5 magnetic catalyst

Addressing environmental challenges and energy resource scarcity, this study focuses on biodiesel production through the transesterification of waste cooking oil with methanol. To facilitate the reaction, a novel heterogeneous catalyst, derived from waste banana peels and composed of biochar-Fe2O3/Fe2K6O5, was employed. The magnetic acid–base catalyst was prepared by carbonating banana peel residue with Fe(III) and potassium hydroxide activator under N2 gas at 700 °C for 2 h. Extensive analysis of the physical and chemical properties of the biochar-based catalyst, including electron microscope analysis, X-ray diffraction, Fourier transform spectroscopy, thermal analysis, and vibration magnetometer techniques, was conducted. The study also explored the influence of crucial parameters on biodiesel yield from waste cooking oil using the biochar-Fe2O3/Fe2K6O5 catalyst. These parameters included the molar ratio of methanol to oil (ranging from 5 to 9 mol/mol), catalyst amount (2–6 wt%), temperature (40–80 °C), and reaction time (1–5 h). Results indicated that optimal conditions for achieving a biodiesel yield of 88.83% were a methanol to oil molar ratio of 7:1, a catalyst amount of 4 wt% for a reaction time of 3 h at 60 °C. The resulting biodiesel exhibited promising properties, including a density of 0.883 g/cm3, a kinematic viscosity of 4.37 mm2/s, and a flash point of 147 °C. The findings of this study highlight the substantial implications and practical benefits of employing rational engineering techniques in the utilization of biochar-Fe2O3/Fe2K6O5 as an exceptionally efficient, stable, and readily recoverable catalyst for the sustainable production of biodiesel from waste oil.