Photoassisted degradation of azodyes over FeOxH2x-3/Fe0 in the presence of H2O2 at neutral pH values

Fe0 was calcined in air at 200 degrees C and showed enhanced activity in three cycling runs for the degradation of acid red B (ARB) in the presence of H2O2 under UVA irradiation. Subsequently, the catalyst's activity was maintained effectively after 10 successive cycling experiments. Moreover, the catalyst was found to be highly effective for the degradation of nonbiodegradable azodyes ARB, reactive brilliant red X-3B, reactive red K-2G, cationic red X-GRL, and cationic blue X-GRL at neutral pH values. On the basis of characterization by X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectra, the surface layer of the catalyst was mainly composed of alpha-FeOOH and gamma-Fe2O3, and the core was Fe0 (FeOxH2x-3/ Fe0). Fe,OxH2x3/Fe0 was very easily recovered from the reaction system by magnetic separation. The degradation of azodyes came from the synergistic effect of the catalysis of galvanic cells and the oxidation of heterogeneous photo-Fenton reaction on the basis of all information obtained under different experimental conditions. By the total organic carbon and GC-MS analysis, the degradation process of ARB was shown to proceed with decolorization and naphthalene ring openings into CO2 and small organic acid.