Production of Biodiesel from Waste Cooking Oil in the Presence of a K₂O/BaFe₂O₄ Nanomagnetic Catalyst

In this paper, BaFe2O4 magnetic nanoparticles were synthesized by the coprecipitation method, and its surface was modified using KOH as a strengthening agent. The catalysts were characterized by the FT-IR, XRD, SEM, TEM, CO2-TPD, BET, TGA/DSC, and VSM techniques. The results indicate that BaFe2O4 and K2O/BaFe2O4 have magnetic behavior at room temperature with a saturation magnetization (Ms) of 33.38 and 27.63 emu g–1, respectively, and both catalysts can be easily separated from the biodiesel reaction system using an external magnet. The nanocatalyst had a supermagnetic property and basicity to catalyze the reaction. The synthesized K2O/BaFe2O4 magnetic nanocatalyst was used to produce biodiesel from waste cooking oil through a transesterification reaction. The results showed that the loading of KOH onto the support and its calcination at a high temperature (650 °C) due to the thermal decomposition of KOH to K2O created strong alkaline sites, which caused higher catalytic activity. The following factors were studied to achieve the most optimal conditions for biodiesel production: reaction temperature, methanol/oil ratio, and amount of loaded catalyst. Under optimal conditions, with a molar ratio of 12:1 methanol/oil, a temperature of 65 °C, and 4 wt % loaded catalyst with 15 % KOH, the production rate of biodiesel was 97.63%. The kinetic modeling and thermodynamic factors were operated on all data and found that the pseudo-first-order kinetic model fits the data well. The activation energies of the reaction over BaFe2O4 and K2O/BaFe2O4 were calculated to be 86.42 and 60.69 kJ mol–1 with rate constants of 0.002 and 0.003 min–1 at 50 °C, respectively.