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Fe3O4 Magnetic Nanoparticles: Characterization and Performance Exemplified by the Degradation of Methylene Blue in the Presence of Persulfate

Abstract In this study, the oxidation of methylene blue (MB) over iron oxide magnetic nanoparticles (Fe3O4), which effectively activates persulfate anions (S2O82−) to form sulfate free radicals (SO4−•), was explored. In addition, the effect of the initial pH, sodium persulfate (Na2S2O8, PS) concentration, and Fe3O4 content on the decolorization of MB was investigated. The results revealed that the decolorization rate increased when the persulfate concentration increased from 0.03 to 0.12 g/L and the Fe3O4 content from 0.1 to 0.8 g/L. Therefore, the Fe3O4 nanoparticles enhanced the decolorization of MB. The catalyst was analyzed using cyclic voltammetry (CV), three-dimensional excitation-emission fluorescence matrix (EEFM) spectroscopy, and zeta potential measurements. The CV spectra indicated that a reversible redox reaction may explain the high catalytic activity of the catalyst. EEFM was used to evaluate the yield of a fresh Fe3O4 catalyst, and two peaks were observed at EX/EM wavelengths of 230/300 nm and 270/300 nm. Furthermore, the structure and surface morphology of the catalyst were characterized using X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM)-energy dispersive spectroscopy (EDS), respectively. The XRD result confirmed the existence of Fe3O4 in the catalyst. ESEM was used to determine the Fe3O4 particle size, indicating a high degree of nanoparticle dispersion.