Waste-Derived Magnetically Recoverable CaO/Metakaolinite/Fe?O? Nanocomposite Catalyst for Efficient Biodiesel Production from Neem Oil
DOI:
https://doi.org/10.63746/njtd.v23i1.4403Keywords:
Magnetic nanocomposite catalyst, Waste-derived CaO, Metakaolinite support, Neem oil biodiesel, Catalyst reusability, Sustainable biofuelsAbstract
The development of sustainable, low-cost, and recyclable heterogeneous catalysts remains a major challenge for large-scale biodiesel production from non-edible oils. In this study, a novel waste-derived, magnetically recoverable CaO/metakaolinite/Fe?O? nanocomposite catalyst was synthesized using eggshell waste, Kutigi kaolin clay, and plant-mediated magnetite through combined impregnation and green synthesis routes. Structural and textural characterization by XRD, HRSEM, HRTEM, BET, FTIR, and DLS confirmed the formation of a crystalline nanoscale composite with enhanced surface area, uniform dispersion of basic CaO active sites, and strong magnetic responsiveness. The catalyst exhibited appreciable basicity (0.5 mmol g?¹; pH 8.1–8.7), enabling efficient transesterification of high free-fatty-acid neem oil. Process optimization using Box–Behnken response surface methodology demonstrated excellent model adequacy (R² = 0.98; Adj-R² = 0.96), achieving biodiesel conversion above 90 wt.% under optimal reaction conditions. Gas chromatography–mass spectrometry confirmed the formation of major fatty acid methyl esters. The produced biodiesel satisfied ASTM D6751 fuel specifications, with density of 890 kg m?³, kinematic viscosity of 4.6 mm² s?¹, flash point of 126 °C, and cetane number of 52. Reusability studies revealed that the catalyst retained approximately 62 wt.% of its initial activity after seven successive cycles, facilitated by efficient magnetic recovery and structural stability. Engine performance evaluation indicated improved brake thermal efficiency for blends up to B20, along with reduced CO and NO? emissions relative to conventional diesel. Overall, the developed magnetic nanocomposite catalyst provides a scalable, environmentally benign, and cost-effective platform for sustainable biodiesel production from non-edible feedstocks.
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