Enhanced photocatalytic activity of FeSO4 in a ZnO photocatalyst with H2O2 for dye degradation

Abstract

In this study, the photocatalytic degradation efficiency of ZnO synthesized by a hydrothermal method and iron-supported ZnO catalysts by an impregnation method, dried (D) and calcined (C), was evaluated, through the degradation of methylene blue (MB) and methyl orange (MO) molecules under UV irradiation. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, and UVvisible diffuse reflectance spectroscopy (DRS). XRD showed that FeSO4 is supported on ZnO, and the XPS study revealed higher concentrations of hydroxyl groups and Fe3+ for the dried catalyst. The bandgap energies were 3.24, 3.23, and 3.19 eV for ZnO, Fe/ZnO D and Fe/ZnO C, respectively. The results revealed that Fe/ZnO D with H2O2 exhibited a higher photocatalytic degradation efficiency than ZnO, achieving 97% and 99% degradation for MB and MO at 10 min, which implies that the integrated iron in ZnO serves as an electron-hole separator. In addition, the catalyst has a larger BET specific area, the presence of hydroxyl groups and sulfate ions on the surface of the catalyst with holes forms hydroxyl radicals (•OH), and the presence of Fe3+ on the surface catalyst with H2O2 produces more •OH radicals. •OH radicals are the major oxidation species in this process, which promotes the degradation of dyes. The photocatalytic dye degradation efficiency was also evaluated for various catalyst doses, dye concentrations and solution pH values. Moreover, the stability of the catalyst over repeated cycles of dye treatment was demonstrated.