Preparation and application areas of magnetic mesoporous TiO2 photocatalysts

Water pollution caused by organic dyestuffs has become a serious problem threatening human health and the natural environment. Frequently used cationic dyes such as Methylene Blue (MB) and Rhodamine B (RhB) have complex aromatic structures and are difficult to degrade into harmless products. In this study, a magnetically separable Fe3O4-SiO2-mezoTiO2 nanocomposite with good photocatalytic degradation performance was prepared for MB and RhB dyes. Fort his purpose, firstly, superparamagnetic Fe3O4 nanoparticles were synthesized using the co-precipitation method. Secondly, SiO2 interlayer was formed around the Fe3O4 nanoparticles by the Stober method in basic medium to prevent the oxidation of these Fe3O4 nanoparticles by air and the reduction of the photocatalytic performance of TiO2. Finally, silica coated nanoparticles were coated with mesoporous TiO2 layer by sol-gel synthesis method using surfactant template. The structural, morphological and magnetic properties of the Fe3O4, Fe3O4-SiO2 and Fe3O4-SiO2-mesoTiO2 samples were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometry (VSM), Infrared Fourier Transform Spectroscopy (FT-IR), N2-adsorption/desorption techniques. At room temperature, under UV irradiation (368 nm), at natural solution pH, with the addition of 50 mg of photocatalyst, MB and RhB decomposed to 97,52% and 99,06%, respectively, after 120 min. The reaction rate constants for both dyes were determined and exhibited good linearity, which indicates fitting of the pseudo-first order rate equation. The reaction mechanism of the photocatalyst is explained for MB and RhB organic dyestuffs by examining a series of radical scavenging effects. Moreover, the magnetic mesoporous TiO2 photocatalyst, which can be separated and recovered with an external magnet, could be reused three times without loos of photocatalytic activity.