The potential of biochar derived from banana peel/Fe3O4/ZIF-67@K2CO3 as magnetic nanocatalyst for biodiesel production from waste cooking oils

Using biomass-based catalysts in biodiesel production can make the process more economical and environmentally friendly. In this study, a new magnetic nanocatalyst was developed using banana peel biochar, ZIF-67, Fe3O4, and K2CO3, and then utilized in a catalytic transesterification process to convert waste cooking oils (WCO) into biodiesel. The level of free fatty acids of the treated WCO (WCOT) was reduced to generate a biodiesel with more suitable characteristics. The physicochemical aspects of the magnetic nanocatalyst were characterized by Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) and map techniques. In the transesterification process, the effect of temperature, methanol-to-oil ratio, process time, and nanocatalyst weight on the potential of nanocatalyst to produce biodiesel from WCO and WCOT was explored. The highest yield of biodiesel from WCO (96.82%) and WCOT (99.18%) was attained at 65 °C, nanocatalyst weight of 3 wt %, methanol-to-oil ratio of 19:1, a processing time of 3 h, and a mixing rate of 600 rpm. Based on thermodynamic studies, the biodiesel production process was endothermic and non-spontaneous. The regeneration of the nanocatalyst was studied using various solvents and n-hexane had a good ability to recover the catalyst (90% up to 5 stages). The results of the 1H NMR test revealed that the desired nanocatalyst had a high potential to generate biodiesel from WCO and WCOT. The properties of produced biodiesel met ASTM D6751 and EN 14214 standards.