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

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 SiO ₂-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.