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The current study focuses on the synthesis of Cerium oxide (CeO2) nanocatalyst via Tragacanth Gum (TG) using the wet impregnation method and its application for sustainable biodiesel production from a novel, non-edible Descurainia sophia (L.) Webb ex Prantl seed oil. The D. sophia seed oil has higher oil content (36 wt%) and free fatty acid (FFA) value (0.6 mg KOH/g). Innovative analytical methods, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy, were used to characterize the newly synthesized, environmentally friendly, and recyclable CeO2-TG phytonanocatalyst (FT-IR). The results show that the CeO2-TG phytonanocatalyst was 22 nm in diameter with a spherical shape outer morphology, while the inner structure was hexagonal. Due to low FFA content, the D. sophia seed oil was pretreated and transesterified via a single step. Using varying parameters, the optimized process variables were determined via Response Surface Methodology (RSM). The optimum process values were 8:1 methanol to oil molar ratio, 0.3 wt% catalyst concentration, 90 °C temperature, and reaction time of 210 min with 98% biodiesel yield. The recently created phytonanocatalyst was reliable and effective, with three times reusability in the transesterification reaction. Thin layer chromatography (TLC), FT-IR, gas chromatography–mass spectroscopy (GCMS), and Nuclear magnetic resonance (NMR) analyses were used to characterize the synthesized biodiesel. Physico-chemical properties of D. sophia biodiesel, i.e., Kinematic viscosity (4.23 mm2/s), density (0.800 kg/m3), pour point (−7 °C), cloud point (−12 °C), and flash point (73.5 °C) agree well with international biodiesel standards (ASTM-6751, 951), (EU-14214), and China (GB/T 20828) standards. The results show that the synthesized nanocatalyst demonstrated remarkable stability, indicating a bright future for industrial biodiesel production from low-cost feedstock. [ABSTRACT FROM AUTHOR]

Highlights: Brassica juncea (L.) Czern. seeds contain 30% oil content and 0.43 mg KOH/g FFA content. Ni-TG nano-catalyst was synthesized through a wet impregnation route. The Ni-TG nano-catalyst has a crystalline size of 39.29 nm with a semispherical and ovoid shape. 0.3 wt% catalyst concentration, 6:1 methanol to oil ratio at 90 °C for 120 min yielded 93% of Brassica juncea (L.) Czern. biodiesel. In the current study, a novel green nano-catalyst from Tragacanth gum (TG) was synthesized and used for sustainable biodiesel production from Brassica juncea (L.) Czern. seed oil. Brassica juncea (L.) Czern contains 30% oil on dry basis and free fatty acid content of 0.43 mg KOH/g. Physiochemical characterization of a newly synthesized nano-catalyst was performed by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. The XRD results showed an average crystalline size of 39.29 nm. TEM analysis showed the cluster form of NiSO4 nanoparticles with a size range from 30–50.5 nm. SEM analysis of the catalyst showed semispherical and ovoid shapes with surface agglomeration. The synthesized catalyst was recovered and re-used in four repeated transesterification cycles. Maximum biodiesel yield (93%) was accomplished at 6:1 methanol to oil molar ratio, catalyst concentration of 0.3 wt%, at 90 °C for 120 min at 600 rpm using Response Surface Methodology (RSM) coupled with central composite design (CCD). Brassica juncea (L.) Czern. biodiesel was characterized by Thin Layer Chromatography (TLC), FT-IR, Nuclear Magnetic Resonance (NMR) (1H, 13C), and Gas Chromatography-Mass Spectroscopy (GCMS) analytical techniques. The major fatty acid methyl esters were 16-Octadecenoic acid and 9-Octadecenoic acid methyl ester. The fuel properties, i.e., flash point (97 °C), density (825 kg/m3 at 40 °C), kinematic viscosity (4.66 mm2/s), pour point (–10 °C), cloud point (–14 °C), sulfur content (66 wt.%), and total acid number (182 mg KOH/g) were according to the International biodiesel standards. The reaction kinetic parameters were determined, and all the reactions followed Pseudo first-order kinetics. It was concluded that non-edible Brassica juncea (L.) Czern. seed oil is one of the sustainable candidates for the future biofuel industry using a cleaner, reusable, and highly active Ni-modified TG nano-catalyst. [ABSTRACT FROM AUTHOR]