Enhancing waste-derived biodiesel yield using recyclable zinc sulfide nanocatalyst: Synthesis, characterization, and process optimization

Abstract

With the increasing demand for sustainable and renewable energy sources, biodiesel has emerged as a promising alternative to conventional fossil fuels. This study presents a novel approach to enhancing Thevetia peruviana biodiesel (TPB) yield from plant waste by optimizing process variables using Zinc sulfide (ZnS) as a catalyst. Co-precipitation was utilized to synthesize the ZnS nanoparticles, followed by comprehensive characterization using SEM, XRD, EDAX, and FTIR. Response surface methodology was employed to determine optimal values for process parameters, specifically catalyst concentration (CC), oil-to-alcohol ratio (OAR), and process temperature (PT). The results demonstrate that the nanoparticle can be effectively reused over five successive cycles without significant loss of catalytic activity. The optimal condition identified was a CC of 107.7 ppm, OAR of 8.9:1, and PT of 94.6 °C, yielding a TPB of 92.5 %, which was validated through confirmation experiments. The yield of TPB using the nanocatalyst exhibited a 3.6 % increase compared to a typical chemical catalyst. ANOVA results revealed that CC had a 43.9 % influence on biodiesel yield, while OAR and PT had influences of 33.2 % and 22.9 %, respectively. Elemental analysis indicated that TPB biodiesel has a 10.9 times higher oxygen concentration compared to diesel fuel, with GC-MS analysis identifying linoleic acid as the predominant component. The elemental, FTIR, GC-MS, and physicochemical analysis of TPB were found to be comparable to the biodiesel standard. This comprehensive assessment suggests that TPB has the potential to serve as a viable alternative to conventional diesel fuel.