Synthesis and Photocatalytic Activity of Magnetically Recoverable Core-Shell Nanoparticles

TiO2/SiO2/Fe3O4 (TSF) core-shell nanoparticles with good photocatalytic activity that are capable of fast magnetic separation have been successfully prepared by chemical coprecipitation and two-step sol-gel process. The as-prepared TSF nanoparticles were calcined at high temperature in order to transform the amorphous titanium dioxide into a photoactive crystalline phase. The calcined nanoparticles are composed of a Fe3O4 core with a strong response to external magnetic fields, a SiO2 intermediary layer, and a TiO2 outshell. Vibration sample magnetometer (VSM) analysis confirms the superparamagnetism of calcined nanoparticles, which can enhance the recoverable properties of the novel photocatalyst. When the TiO2/SiO2 /Fe3O4 core-shell nanoparticles are added to the crude oily wastewater, they exhibit high photocatalytic activity in the degradation of crude oily wastewater. The oil concentration could be reduced to lower than 30 ppm within 20 minutes for the case of initial oil concentration less than 350 ppm. It has been found that the TSF nanoparticles could be easily separated from the wastewater and withdrawn by using an external magnetic field. The recovered TSF nanoparticles possess high efficiency in the degradation of crude oily wastewater even after three times successive reuse. The present results indicate that TSF core-shell nanoparticles possess great application perspectives in the degradation of crude oily wastewater.