Insight into the enhanced magnetic separation and photocatalytic activity of Sn-doped TiO2 core-shell photocatalyst

Much attention has been focused on the synthesis of TiO2 based materials as photocatalysts for water pollutant treatment, it still needs overcome difficulties of separation of TiO2 photocatalyst from the treated water and the recombination of photo-induced carriers to improve catalytic activities. In this paper, a magnetical core-shell Fe3O4@SiO2@Sn-TiO2 (FST-S) composite photocatalyst was designed and prepared via prepared via Stober and sol-gel methods. The effect of Sn2+ coating TiO2 on the surface of Fe3O4@SiO2 nanoparticles was principally investigated. The photocatalytic performance and recyclability of FST-S were evaluated by photodegradation of tetracycline hydrochloride (TC). Experimental results show that Sn2+ doping increased the content of TiO2 in composite photocatalyst. Because some Sn2+ ions lead to the decrease in the stability of Sn2+-TiO2 nanoparticles and then low-stable Sn2+-TiO2 nanoparticles enter into the composite photocatalyst by condensation with the Sn2+-TiO2 outer shells of FST-S. The photodegradation results show that FST-S sample exhibits an outstanding photocatalytic capacity with a superior degradation rate of 98.2% within 40 min and a good reusability without significant decrease of activity after reused for six cycles. The reaction rate constant (k) of the FST-S was 3.86 times compared with that of without Sn doping Fe3O4@SiO2@Sn (FST). Reactive species scavenging experiments revealed that O-2(-center dot) it plays a dominant role in photodegradation process. The distinct enhancement of photo catalytic activity of Fe3O4@SiO2@Sn-TiO2 is mainly ascribed to the high amount of TiO2 and low recombination rate of photogenerated electron-holes. This work initiates a novel strategy to prepare magnetical core-shell photocatalysts with excellent activity.