Synthesis and characterization of TiO2/Fe2O3 and TiO2/SiO2@Fe2O3 magnetic photocatalysts: implications for photodegradation of organic compounds

Abstract

In the present work, magnetic photocatalysts were prepared, containing different quantity of TiO2, supported on ferroxite (δ-FeOOH) and on a core-shell structure of silica and ferroxite (SiO2@δ-FeOOH), obtaining materials 30, 50 and 80% Ti/Fe and 30, 50 and 80% Ti/Si@Fe. These, conserned to obtain materials that absorb in the region of the visible and of easy recovery. The Thermogravimetric Analysis (TG) and Differential Scanning Calorimetry (DSC) indicating that the ferroxite suffer dehydroxylation during the thermal treatment to obtain the final photocatalysts, the X-ray diffraction (XRD) shows that maghemite (γ-Fe2O3), magnetic part, and hematite (α-Fe2O3) were formed, besides confirming the anatase and rutile phases present in TiO2. These materials were also morphologically evaluated by Transmission Electron Microscopy (TEM), that confirms the structure of the core-shell type, which is also indicated by the Attenuated Total Reflection (ATR) and Scanning Electron Microscopy (SEM) shows TiO2 agglomerates supported on the surface of the magnetic oxide. The magnetization of these materials was visualized by Vibrating Sample Magnetometer (VSM) and by Sedimentation Kinetics, which indicated that the magnetism present in the samples facilitates the recovery of these materials in reaction. The surface areas of these materials are not affected by the oxides junction, since they do not undergo major changes. Through the bandgap investigation of the photocatalysts, it was observed that there was a decrease of energy after the incorporation of iron and core-shell silica and iron, increasing the absorption of energy in the visible region. Methylene Blue (MB) photodegradation reactions were performed in the presence of sunlight (1.600 mW.cm -2 ) and in the presence of UV-C radiation 51 W (1.270 mW.cm -2 ) using the synthesized materials, and these present good photocatalytic efficiency, reducing the color of the dye.