Characterization of iron oxide nanoparticles obtained from robinia pseudoacacia L. fruit extracts by green synthesis method and investigation of dye removal performances from water

Bioremediation is a sustainable method that aims to convert environmental pollutants into harmless components using various organisms. In recent years, nanoparticles synthesized through green methods have been widely employed in bioremediation applications. As an environmentally friendly alternative to physical and chemical synthesis methods, green synthesis is carried out using biological materials. Nanoparticles synthesized through this method consist entirely of biologically derived natural components, instead of toxic chemicals. In this study, iron oxide (Fe₃O₄) nanoparticles were green-synthesized from the non-economic fruits of Robinia pseudoacacia L., widely used in afforestation and landscaping in Türkiye, and subsequently characterized. The structural, functional, and optical properties of the nanoparticles were analyzed using UV-Vis spectrophotometry, transmission electron microscopy/energy-dispersive X-ray spectroscopy (TEM/EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) techniques. The obtained data indicate that the synthesized Fe₃O₄ nanoparticles are less than 10 nm in size and have an amorphous structure. The effectiveness of the fruit extract and its derived Fe₃O₄ nanoparticles in removing methylene blue (MM), phenol red (FR), and malachite green (MY) from aqueous solutions was also evaluated. The highest dye adsorption capacity was obtained in the MM solution; over 97% removal efficiency and high adsorbed amount (Qₑ) values at low and moderate initial concentrations were observed. Among the three dyes, FR exhibited the lowest adsorption capacity, while high removal rates up to 99% were recorded for MY. The findings indicate that green-synthesized Fe₃O₄ nanoparticles from Robinia pseudoacacia fruits are promising adsorbents for environmental pollutant removal.