Biodiesel production from waste frying oil via NiFe2O4/SiO2 magnetic nanocomposites: Evaluation of diesel engine parameters and statistical optimization

Magnetic nanocatalysts NiFe₂O₄/SiO₂ and NiFe₂O₄ were synthesized using the sol-gel technique. It's used to generate biodiesel from waste frying oil (WFO) through transesterification. Multiple methods were used to characterize the nanocatalysts, including XRD, BET-BJH, SEM, EDX, VSM, FTIR, and TEM. The spherical shape of the magnetic NiFe₂O₄/SiO₂ nanocatalyst was evident, with an average nanoparticle diameter of 51.6. The impact of different characteristics was explored using response surface methodology and Box-Behnken design (RSM-BBD). The optimal parameters for biodiesel production were achieved with reaction times of 204 min for NiFe₂O₄ and 228 min for NiFe₂O₄/SiO₂, catalyst concentrations of 2.07 and 2.04 %, and methanol/WFO ratios of 11.5 and 11.58, respectively. Under optimal conditions, the maximum biodiesel production for NiFe₂O₄ and NiFe₂O₄/SiO₂ nanocatalysts was 95.16 and 97.23 %, respectively. The catalyst's reusability over seven cycles showed an 88.56 % decrease in biodiesel production, indicating the NiFe2O4/SiO2 nanocatalyst's stability. Additionally, the kinetics and thermodynamics of the transesterification process revealed that the reaction is characterized as endothermic and non-spontaneous. 1H NMR and FT-IR spectra confirmed the transesterification process that converts WFO into biodiesel. Incorporating Waste Frying Oil Methyl Ester (WFOME) and NiFe₂O₄/SiO₂ into diesel at various engine loads generated significant improvements in engine performance and reductions in emissions.