Influence of calcination temperature on structure, magnetic property, photocatalytic activity and recovery of recyclable photocatalysts

The photocatalytic oxidation of titanium dioxide is conducted in a suspension of submicrometersized particles, and an additional separation step is required to recover these catalyst particles from treated water, which presents a major drawback in treating wastewater. In this study, magnetic photocatalysts of spinel structure Fe₃O₄ coated with SiO₂ and TiO₂ by employing various heat treatments were synthesized and their characterization was carried out by thermogravimetric analysis, X-ray diffraction, vibrating sample magnetometry, and Fourier transform infrared spectroscopy. Furthermore, the reaction behavior in photocatalytic processes involving photocatalysts of porous composite for treating wastewater were analyzed to enhance their activity and recovery. The results showed that the calcination temperatures of the magnetic photocatalysts significantly affect their properties, i.e., rutile ratio, magnetization, surface area, and photocatalytic activity. The photocatalytic activity of these catalysts was measured using the decomposition of benzoic acid, which can be well modeled by the Langmuir-Hinshelwood kinetic equation. Furthermore, because of the paramagnetic behaviors of the prepared TiO₂/SiO₂/Fe ₃O₄, these magnetic photocatalyst could be easily recovered by applying a magnetic field.