Sustainable biodiesel production from Oenothera lamarckiana oil using hybrid [email protected] magnetic nanocatalyst: RSM-driven optimization

• Biodiesel was synthesised from Oenothera lamarckiana oil using a hybrid CaO@Fe 3 O 4 .SiO 2 nanocatalyst. • Response Surface Methodology (RSM) optimized the reaction conditions yielding 98.4% biodiesel. • The catalyst retained efficiency after seven cycles, demonstrating excellent reusability. • Kinetic and thermodynamic analyses revealed a pseudo-first-order reaction with favorable activation energy. Converting novel and under-exploited inedible oil in the presence of hybrid Nano catalysts (NCs) has significant economic and environmental benefits. The study undertook Oenothera lamarckiana seed as a non-edible feedstock, yielding 28% crude oil via Soxhlet extraction technique and hybrid CaO@Fe 3 O 4 .SiO 2 NC was synthesized through a hydrothermal process and characterized using techniques like XRD, TEM, SEM, EDX, FTIR, BET-BJH, TGA/DTA, and VSM, confirming its core-shell structure and catalytic properties. RSM conjunction with the CCD was employed to get the statistical model, four process input variable and five level factors were generated. The desirability function approach (DFA) determined the optimal transesterification reaction (molar ratio of 14.22:1, catalyst concentration of 3.85 wt.%, temperature of 66.53°C, and reaction time of 125.98 minutes) resulting in the highest biodiesel conversion of 98.8%. Compared to conventional catalysts, the hybrid NC showed improved reaction efficiency and maintained high performance over seven cycles with excellent reusability. The biodiesel tested against quality meets the ASTM standards . Chemical analysis via GC-MS and ¹H NMR confirmed a high oleic acid methyl ester content, enhancing cold flow, cetane number and oxidative stability. Kinetic investigations showed a pseudo-first-order reaction with 55.928 kJ/mol activation energy. Thermodynamic analysis revealed the reaction's endothermic nature, increasing Gibbs free energy (ΔG = 94.163–96.401 kJ/mol), highlighting the need for external energy inputs. The catalysts reusability with magnetic separation ensures the process is cost-effective and suitable for large-scale industrial biodiesel production. The combination of novel feedstocks and advanced NCs holds a greatest potential for cleaner biofuel production, contributing to both energy security and environmental sustainability.