Green synthesis of strontium-doped ZnO nanocatalyst using Guiera senegalensis leaf extract for biodiesel production from waste cooking oil

Résumé fourni par la source

Waste cooking oil (WCO) is an increasingly useful raw material for biodiesel because its use can lower dependence on edible feedstocks and reduce disposal-related environmental problems. A major limitation, however, is its free fatty acid (FFA) content, which may interfere with conventional alkaline-catalyzed transesterification through soap formation. In this work, a strontium-modified zinc oxide (Sr-doped ZnO) nanocatalyst was prepared by a plant-mediated route using Guiera senegalensis leaf extract. The material was examined by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). FTIR indicated hydroxyl-containing surface species together with bands assigned to Sr–O and Sr–O–Zn interactions, whereas XRD showed the characteristic hexagonal wurtzite ZnO structure. The mean crystallite size was 18.2 nm. SEM examination showed agglomerated, flower-like particles with a rough and porous appearance, while EDX detected Zn, O, and Sr. A central composite design (CCD) within response surface methodology (RSM) was applied to study the effects of methanol quantity, catalyst loading, and reaction time on biodiesel yield. Of the 20 experimental runs, the highest reported yield was 89.88% at 6.6 mL methanol, 0.138 g catalyst, and 180 min. Kinetic experiments conducted at 318, 328, and 338 K indicated that the pseudo-first-order model gave the best fit among the models considered, with rate constants of 0.0073, 0.0078, and 0.0081 min−1, respectively. The Arrhenius treatment gave an activation energy of 15.07 kJ mol−1. These findings suggest that the green-synthesized Sr-doped ZnO is a promising heterogeneous catalyst for converting WCO to biodiesel. Nevertheless, catalyst recycling, stability, and biodiesel quality require further investigation before practical industrial deployment can be confirmed.

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