Photocatalytic degradation of dyes on a magnetically separated photocatalyst under visible and UV irradiation

Abstract

A novel kind of magnetically separable photocatalyst of TiO 2/SiO 2/γ-Fe 2O 3 (TSF) is prepared. Scanning tunnel microscope (STM) and X-ray diffractometer (XRD) were used to characterize the structure of the photocatalyst. In the TSF photocatalyst, a TiO 2 shell is for photocatalysis, a γ-Fe 2O 3 core as a carrier is for separation by the magnetic field and a SiO 2 membrane between the TiO 2 shell and the γ-Fe 2O 3 core is used to weaken the adverse influence of γ-Fe 2O 3 on the photocatalysis of TiO 2. Three kinds of dyes, Fluoresein, Orange II and Red acid G, were used to examine the photocatalytic activity of TSF. Due to strong UV adsorption of the γ-Fe 2O 3, the photocatalytic activity of TSF was lower than that of the pure TiO 2. Deducting the light absorption of the γ-Fe 2O 3 particles, the photocatalytic activity of TSF was found to be higher than that of the P25 under UV irradiation. On the other hand, the photocatalytic activity of TSF under visible irradiation was much lower than that of the P25 TiO 2 even deducting the visible light absorption of the γ-Fe 2O 3 particles. Differences in the photocatalytic mechanisms under UV and visible irradiation lead to the differences in the photodegradation characteristics of dyes on TSF. The recycled TSF exhibited a good repeatability of photocatalytic activity.