Preparation and characterization of magnetic-core titanium dioxide: Implications for photocatalytic removal of ibuprofen

Abstract

Magnetically separable titanium dioxides (MSTs) were synthesized from nano-magnetite (Fe3O4), tetraethyl orthosilicate (TEOS), and titanium butoxide (TBT) using a sol-gel process, and their activity in the photocatalytic oxidation of ibuprofen (IBP) was evaluated. Transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) revealed that the thickness of TiO2 layers was linearly dependent on the TBT content, producing predictable results. As the ratio of TBT (mL) to TEOS (mL) increased, the purity of the TiO2 layers of the prepared MSTs increased owing to the absence of Si compounds. Based on TEM-EDS, X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy analyses, TiO2 in MSTs was successfully coated on the surface of amorphous SiO2 with Fe3O4 as the core. Magnetization of the MSTs declined exponentially with increasing thickness of the non-magnetic SiO2-TiO2 layer. The optimal loading and activation energy of MSTs were also determined for photocatalytic removal of IBP. Comparison of the kinetic constants suggests a positive relationship between photocatalytic activity and surface area. Increased aggregation of the MSTs with higher magnetization values was attributed to stronger magnetic dipole-dipole interactions. The results of this study provide an in-depth understanding of the synthesis of magnetically separable catalysts satisfying the requirements of both magnetic separation and photocatalytic activity with potential application in the removal of recalcitrant organic pollutants. (C) 2014 Elsevier B.V. All rights reserved.