A Novel Heterogeneous Photo-Fenton Fe/Al2O3 Catalyst for Dye Degradation

The activity of heterogeneous photo-Fenton catalysts based on iron and supported on commercial alumina was studied for the degradation of rhodamine B, methyl orange and methylene blue under UV irradiation. The catalysts were prepared by impregnation, drying, and calcination or omitting this last step and referred to as dried or calcined samples. All samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N-2 adsorption-desorption, diffuse reflectance UV-vis absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). The XRD results revealed that all catalysts showed peaks of alpha-Al2O3 and FeSO4. The band gap of the catalysts compared with alumina decreased, due to the presences of Fe species which functioned as traps inhibiting the electron-hole recombination. The XPS results revealed the presence hydroxyl groups on the surface and the presence of both Fe3+ and Fe2+ in both catalysts. The photodegradation experiments showed that the heterogeneous photo-Fenton process was much faster compared with the hetemgenous photocatalyst on all the tested dyes. The dried Fe/Al2O3 with the presence of H2O2 under UV irradiation showed the best degradation of rhodamine B, methyl orange, and methylene blue at 99.6, 100, and 99.1% at 5, 10, and 5 min, respectively. This could probably be ascribed to a good dispersion of Fe particle species on Al2O3, a low band gap and a proper concentration of hydroxyl groups and sulfate groups on the surface. The scavenger test revealed that the hydroxyl radicals played the main role in the photodegradation of dyes in this process compared with the superoxide radicals and positive holes.