Magnetic biochar Fe3O4/ZnO NPs@K2CO3 nanocomposite as an efficient catalyst for biodiesel production from blended oil

In this study, magnetic biochar-based composite of Ziziphus mauritiana leaf, Fe 3 O 4 , ZnO nanoparticles and K 2 CO 3 could efficiently catalyze the transesterification of waste edible and non-edible oil mixture. This study explores the use of magnetic biochar–Fe 3 O 4 /ZnO NPs@K 2 CO 3 as a composite catalyst, offering a novel perspective on biodiesel production. The catalyst was synthesized, and characterized using various techniques, including powder X-ray diffraction (XRD), Ultraviolet (UV) spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), Vibrating sample magnetometer (VSM), Thermogravimetric analysis (TGA), High-resolution transmission electron microscopy (HRTEM), Field emission scanning electron microscopy (FESEM) and Brunauer–Emmett–Teller (BET). Optimal reaction conditions were determined to be as 10 wt% catalyst amount, molar ratio of methanol-to-oil (MRMO) of 9:1 and 65 °C reaction temperature. Under these conditions, the process achieved a biodiesel yield of 94.68 ± 1.27% within 54.66 ± 1.20 min. The catalyst demonstrated good reusability, retaining 82.24 ± 1.67%biodiesel yield after 3rd recycled. The produced biodiesel was assessed by FT-IR, GC–MS, 1 H NMR and 13 C NMR analyses, confirming the successful formation of fatty acid methyl esters (FAMEs). The measured fuel properties complied with standard biodiesel specifications, indicating the suitability of the produced biodiesel for practical fuel applications. Future studies should focus on improving catalyst stability over extended reuse cycles, evaluating catalyst leaching behavior, performing kinetic and life-cycle assessments and investigating large scale applications to assess industrial feasibility and long-term sustainability.