352 INTRODUCTION Biodiesel is a renewable fuel which contain mono-alkyl esters resulting from long-chain fatty acids, typically sourced from vegetable oils or animal fats. Its sustainable nature and lower emis- sions of greenhouse gases and particulate matter make it a strong alternative to conventional diesel. Additional benefits include excellent lubricating properties, a high cetane number, elevated flash point, and significant biodegradability. While edible oils have been examined for biodiesel production, their cost-intensive feature presents a substantial barrier. Therefore, researchers have started diverting their attention to more affordable alternatives, like non-edible oils Jatropha curcas and waste cooking oils. Oil yield is one of key factors considered in choosing an appropriate biodiesel feedstock. It is believed that the crops producing higher quantity of oil are preferred due to lower production costs [Baskar and Soumiya, 2016]. Biodiesel is produced via transesterifica- tion, which involves triglycerides and alcohol re- acted in the presence of a nanocatalyst. During Facile synthesis and catalytic evaluation of iron-doped zinc oxide nanocatalysts for biodiesel production Jaffar Hussain 1* , Zeenat Muhammad Ali 1 , Farman Ali Shah 1 , Abdul Qadeer 1 , Abdul Nasir Laghari 2 , Munazza Sohil 3 1 Department of Chemical Engineering Mehran University of Engineering and Technology, Jamshoro, 76062, Pakistan 2 Department of Chemical Engineering Quaid-e-Awam University of Engineering Science and Technology Nawabshah, Pakistan 3 Pakistan Council of Scientific and Industrial Research (PCSIR) Karachi, Pakistan * Corresponding author’s e-mail: jafarkhosa72@yahoo.com ABSTRACT The global transition in energy consumption patterns driven by the depletion of fossil fuel reserves, rapid pop- ulation growth, and increasing environmental pollution has faster the exploration for renewable and ecological energy substitutes. Among these, biodiesel has materialized as a capable candidate due to its carbon-neutral profile, environmental compatibility, and potential as a cleaner alternate for conventional petroleum-based diesel. In this study, the performance of iron(II)-doped zinc oxide (Fe(II)-ZnO) nanocatalyst was investigated for biodiesel pro- duction from Jatropha curcas oil. The nanocatalyst was synthesized and characterized using atomic force micros- copy (AFM), fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and zeta potential analysis. AFM analysis revealed pronounced surface topography with elevated features reaching up to 50 nm in height. The formation of Zn–O and Fe–O bonding was affirmed through FTIR spectra, while XRD analysis demonstrated the presence of crystalline phases corresponding to Fe₂O₃ and ZnO, with the most intense diffraction peak observed at 2θ = 35.8777°. Zeta potential measurements indicated moderate colloidal stability with a measured value of –4.01 mV. The Jatropha curcas oil used in the transesterification process possessed a density of 909 kg/m³ at 25 °C, an acid value of 1.20 mg KOH/g, and a viscosity of 25.63 mm²/s.. Transesterification was carried out under optimized reaction conditions, comprising a methanol-to-oil molar ratio of 12:1, reaction temperature of 50 °C, catalyst loading of 2% Fe(II)-ZnO, and a reaction time ranging from 10 to 180 minutes. The produced biodiesel exhibited a density within the ASTM D6751 standard specifications. While the flash point was slightly elevated making it suitable for blending with petro-diesel the viscosity remained marginally higher than standard diesel fuel. Keywords: nanoparticle, renewable energy, iron oxide, nanocatalyst, biodiesel. Received: 2025.06.03 Accepted: 2025.07.15 Published: 2025.07.22 Journal of Ecological Engineering, 2025, 26(10), 352–359 hps://doi.org/10.12911/22998993/206962 ISSN 2299–8993, License CC-BY 4.0 Journal of Ecological Engineering