Long-term stability of Anacardium occidentale L. extract for green synthesis of iron oxide nanoparticles applied to 4-nitrophenol reduction

The contamination of wastewater by nitroaromatic compounds, such as 4-nitrophenol (4-NP), poses a significant environmental challenge due to their toxicity and persistence. This study investigates the green synthesis of iron oxide nanoparticles (FeONPs) using aqueous extracts from Anacardium occidentale L. (cashew) as a sustainable reducing and stabilizing agent. We evaluated the influence of extract storage time (up to 60 days at -20°C) and different energy sources (water bath, microwave, ultrasound, and UV radiation) on the synthesis efficiency and physicochemical characteristics of the FeONPs. The synthesized nanoparticles were characterized by UV-Vis spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR-ATR), dynamic light scattering (DLS), and Zeta potential analysis. Results indicated that the extract remains viable for synthesis even after 60 days of storage, offering a robust and practical approach for sustainable nanoparticle production. Furthermore, the synthesis method significantly influenced particle formation. The produced FeONPs demonstrated efficient catalytic activity in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol in the presence of sodium borohydride, offering an eco-friendly alternative for environmental remediation.