Degradation of Acid Orange 7 using magnetic AgBr under visible light: The roles of oxidizing species

AgBr was creatively immobilized on a magnetic substrate (SiO2-coated Fe3O4 nanoparticle, SFN) to achieve magnetic separation after visible light-driven photocatalytic oxidation (PCO). The resulted Ag/AgBr/SFN was characterized by TEM, vibrating sample magnetometer and other techniques. It is found that the average diameter of the Ag/AgBr/SFN particle is less than 20 nm. The typical superparamagnetic behavior of Ag/AgBr/SFN implies that the catalyst can be magnetically separated. The physicochemical features of the used Ag/AgBr/SFN after visible light irradiation were not dramatically changed by X-ray diffraction, UV–Vis diffuse reflectance spectra and Fourier transform-infrared analysis. SiO2 interlayer was proven to slightly increase the degradation efficiency for an azo dye Acid Orange 7. UV–Vis spectra and HPLC analysis indicated that the dye was oxidized and decomposed. The photoactivity of Ag/AgBr/SFN was partly maintained after successive PCO under visible light. In order to evaluate the roles of e−–h+ pairs and reactive oxygen species, the quenching effect was examined by employing Ag/AgBr/SFN and commercial TiO2 (P-25) under visible light (λ > 400 nm) and UV-A irradiation, respectively. Active h+ and the resulting OH played the major roles for degradation. The effect of active h+ and OH were proven to be highly dependent on the concentration of photocatalysts. The effect of OH was more obvious for P-25, while that of active h+ was more predominant for Ag/AgBr/SFN.