Repurposing Citrus paradisi L. waste seed oil in the renewable production of biodiesel using phytosynthesized lead oxide nanoparticles

Global interest in developing a state-of-the-art circular economy has been driven by the desire to generate bioenergy and bioproducts from biowaste streams. Biodiesel, synthesized from used, non-edible oils has emerged as a sustainable and ecofriendly alternative fuel for diesel engines. This study investigates the feasibility of employing an innovative circular economy to convert waste Citrus paradisi L. seed oil into sustainable biodiesel using green lead oxide nanoparticles (PbONPs). The synthesized biodiesel is noted for its ecofriendly characteristics, being non-toxic, biodegradable, cost effective and comparable to traditional petroleum-based diesel. PbONPs were prepared using aqueous leaf extract of Nasturtium officinale L. Analytical characterization of PbONPs revealed an average particle size of 42 nm. PbONPs demonstrated recyclability with maximum catalytic activity maintained through four consecutive cycles of transesterification. An optimal yield of 93 % was achieved under specific reaction conditions: a methanol-to-oil molar ratio of 7:1, a reaction time of 105 min, a temperature of 92.5 ˚C, and a catalyst load of 0.32 wt%. The predominant fatty acid methyl ester identified in the biodiesel was 5, 8-octadecadienoic acid methyl ester. The biodiesel produced from C. paradisi met the criteria for international standards with an impressively low sulfur content of 0.0001 %, underscoring its clean and benign nature.