Utilization of waste seed oil from Cestrum nocturnum as a novel source for cleaner production of biodiesel using green nano-catalyst of antimony oxide

•Conversion of biomass waste of Cestrum nocturnum into renewable energy.•Synthesis of Sb2O3 NPs using Chenopodium album leaf extract.•Optimization of transesterification via Response Surface Methodology.•The highest yield (94%) of methyl ester was produced. Presently, the world faces pressing global challenges encompassing social, economic, and sustainable development, all of which demand a growing scale of energy production and associated services. With abundant waste biomass at our disposal, there exists immense potential for harnessing it to produce biofuels. In this study, we synthesized biodiesel using waste seed oil from Cestrum nocturnum, employing a green nano catalyst composed of antimony oxide (Sb2O3NPs). Active ingredients were extracted from the leaf of Chenopodium album and used as a reducing agent. Using Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Disperse X-ray Spectroscopy (EDX), Transmission Electron Microscopy (TEM) and Thermogravimetric Analysis (TGA), the synthesized Sb2O3 nanoparticles was characterized for chemical composition, functional groups, crystalline structure, and thermal stability. Additionally, the produced biodiesel was quantitatively evaluated using Nuclear Magnetic Resonance Spectrometry (1H and 13C NMR) and Gas Chromatography Mass Spectrometry (GC–MS). The highest yield (94 %) of methyl ester was obtained at optimum reaction conditions of 0.56 wt% of the catalyst, methanol to oil molar ratio of 8:1, at 95 °C for 180 min. Fatty acid profiles of synthesized biodiesel revealed elevated levels of 9-octadecenoic acid content. The cold properties (pour point, −11 °C and cloud point, −8 °C) and flash point (99 °C) of the biodiesel were within international requirements. The reusability of Sb2O3NPs revealed a maximum catalytic performance up to 5 cycles. The conversion of waste seed oil from Cestrum nocturnum to clean bioenergy has shown to be a successful waste management strategy for mitigating environmental pollution.