Preparations and photocatalytic degradation of Methyl orange in water on magnetically separable Bi12TiO20 supported on nickel ferrite

Shihong Xu
Research Center for Combustion and Environment Technology, Shanghai Jiao Tong University

Wenfeng Shangguan
Research Center for Combustion and Environment Technology, Shanghai Jiao Tong University

Jian Yuan
Research Center for Combustion and Environment Technology, Shanghai Jiao Tong University

Jianwei Shi
Research Center for Combustion and Environment Technology, Shanghai Jiao Tong University

Mingxia Chen
Research Center for Combustion and Environment Technology, Shanghai Jiao Tong University

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     Last modified: February 15, 2006

Abstract
Semiconductor photocatalysts, mainly TiO2, have attracted much attention in last decade because of their potential application in the removal of all kinds of organic and inorganic pollutants in water. A slurry type reactor is the most commonly applied method because of its high specific surface area and dispersion. However, the use of the slurry reactor is still limited mainly due to difficult separation of TiO2 particles from treated water. Moreover, TiO2 photocatalyst is only active under UV light, which accounts for only about 5% of the solar spectrum at the earth’s surface. In order to improve the efficiency of utilizing the solar energy for photocatalytic treatment of wastewater, the development of visible light-driven photocatalysts is indispensable.
The paper reports a magnetically separable photocatalyst Bi12TiO20/SiO2/NiFe2O4 (BSN) for wastewater treatment. The nano-composited photocatalyst was prepared by a simple process: the magnetic SiO2/NiFe2O4 (SN) dispersion prepared by a liquid catalytic phase transformation method and the visible-light-active photocatalyst Bi12TiO20 prepared by a simple coprecipitation processing were mixed, sonificated, dried, and calcined at 550 °C. The prepared photocatalyst showed high photocatalytic activity for the degradation of Methyl orange in water under UV irradiation and visible light irradiation (λ > 400 nm), and it was easy to be separated from a slurry-type photoreactor under the application of an external magnetic field, being one of promising photocatalysts 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) particles adhered to the surface of the Bi12TiO20 congeries. SiO2 membrane round the surface of NiFe2O4 nanoparticles prevented effectively the injection of charges from TiO2 particles to NiFe2O4, which gave rise to the increase in photocatalytic activity.