Preparation and Photocatalytic Properties of Magnetically Separable TiO2 Supported on Nickel Ferrite*

A magnetically separable photocatalyst TiO2/SiO2/NiFe2O4 (TSN) with a typical ferromagnetic hysteresis was prepared by a liquid catalytic phase transfer method. When the intensity of applied magnetic field weakened to zero, the remnant magnetism of the prepared photocatalyst faded to zero. The photocatalytst can be separated from water when an external magnetic field is added and redispersed into aqueous solution after the external magnetic field is eliminated, that makes the photocatalysts promising for wastewater treatment. Transmission electron microscope (TEM) and X-ray diffractometer (XRD) were used to characterize the structure of the photocatalyst, indicating that the magnetic SiO2/NiFe2O4 (SN) particle was compactly enveloped by P-25 titania and TiO2 shell was formed. The magnetic composite showed high photocatalytic activity for the degradation of methyl orange in water. A thin SiO2 layer between NiFe2O4 and TiO2 shell prevented effectively the leakage of charges from TiO2 particles to NiFe2O4, which gave rise to the increase in photocatalytic activity. Moreover, the experiment on recycled use of TSN demonstrated a good repeatability of the photocatalytic activity.