Application of Fe3O4/SiO2@ZnO magnetic composites as a recyclable heterogeneous nanocatalyst for biodiesel production from waste cooking oil: Response surface methodology

Abstract

Fe3O4/SiO2@ZnO nanocomposite was synthesized using the co-precipitation method and then used as an efficient and reclaimable heterogeneous catalyst for biodiesel generation from waste cooking oil (WCO). The surface features of the nanocomposite were determined with XRD, FT-IR, Mapping, EDX, FESEM, BET, TEM, and VSM approaches. The specific surface area, mean particle size, and pore volume of Fe3O4/SiO2@ZnO were estimated to be 32.56 m2 g −1, 10.46 nm, and 0.15 cm3 g−1 respectively. The results of nanocatalyst characterization indicated that the distribution of Si and Zn elements in the lattice of Fe3O4 nanoparticles has been done successfully. The response surface methodology (RSM) and Box-Behnken design (BBD) were applied to design the experiment, statistical modeling, and optimization. The R2 value for RSM was found to be 0.9941, which indicates that the model is remarkably consistent with the experimental data. The maximum biodiesel yield for the synthesized nanocatalyst was achieved at 97.23% under optimum conditions, including methanol to oil molar ratio of 9.90:1, ultrasonic irradiation time of 30.13 min, and nanocatalyst dosage of 2.67 wt%. The stability assessment illustrated that the nanocatalyst can be efficiently reutilized for seven cycles (yield of 88.36%). Furthermore, it can be concluded that the Fe3O4/SiO2@ZnO nanocatalyst can be applied as an efficient and promising heterogeneous catalyst in biodiesel generation from WCO.