Eco-engineered copper oxide nanoparticles using Moringa oleifera pod's aqueous extract for biodiesel synthesis: green synthesis and process optimization

Biodiesel is viable, and environmentally friendly alternative to petroleum-based diesel, with potential to significantly reduce noxious greenhouse gas emission. This research study explores and evaluates for the first time the use of phytochemicals present in the agricultural residue of the pod of the Moringa oleifera tree for the synthesis of copper oxide nanoparticles (CuO NPs). The CuO NPs was used as a heterogeneous catalyst to produce biodiesel from sunflower oil. Aqueous extract of the M. oleifera pod, which as rich in phytochemicals was obtained at 100 °C and 60 min under stirring. The extract was mixed with precipitated CuO under vigorous stirring and then calcined to obtain CuO NPs. Phytochemical screening of the M. oleifera extract revealed the presence of phenols, saponins, carbohydrates, and flavonoids. The crystalline structure of CuO NPs is monoclinic with an average particle size of 14 nm and spherical-agglomerated surface morphology. The CuO NPs has mainly mesopores with surface area of 48.750 m 2 g -1 . About 95.3% biodiesel yield was achieved under Taguchi designed optimized conditions and the catalyst can be reused for 7 cycles with minimal lose in catalytic performance. The physicochemical properties of sunflower biodiesel satisfactorily comply with the values established by the ASTM. • Moringa oleifera pods was used for the first time to synthesize CuO nanoparticles. • The CuO NPs catalyst showed 48.75 m 2 /g surface area and mesoporosity. • The maximum biodiesel yield was 95.3% under optimized conditions. • The heterogeneous CuO catalyst can be reused for 7 consecutive cycles.