Catalytic Potential of Green-Synthesized Iron Nanoparticles from Psidium guajava for 4-Nitrophenol Reduction

ABSTRACT: This study presents a sustainable approach for the green synthesis of iron nanoparticles (Fe(NPs)) using an aqueous extract of Psidium guajava (guava leaves) as a reducing and stabilizing agent. The FeNPs were applied in the catalytic reduction of 4-nitrophenol. To minimize the use of sodium borohydride (NaBH₄), different volumetric ratios of plant extract and NaBH₄ were tested. The influence of these ratios on the physicochemical and morphological properties of the FeNPs was evaluated using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), high-resolution field-emission SEM (HR-FESEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and N₂ physisorption. Increasing the proportion of plant extract led to reduced crystallinity, larger particle sizes, and lower surface areas. Despite these changes, using up to 40% extract improved catalytic performance, achieving over 90% reduction of 4-nitrophenol. Ecotoxicological assessments confirmed the biocompatibility of the FeNPs, the effective neutralization of 4-nitrophenol toxicity post-reduction, and highlighted the inherent toxicity of NaBH₄. These findings demonstrate the potential of Psidium guajava-mediated FeNPs as eco-friendly catalysts for pollutant reduction, combining efficiency with reduced environmental impact.