Synthesis, characterization and photocatalytic efficiency of Fe3O4/SiO2/TiO2, SrFe12O19/SiO2/TiO2 and Fe3O4/SiO2/ZnO core/shell/shell nanostructures

In this research, three magnetically separable photocatalysts, Fe3O4/SiO2/TiO2, SrFe12O19/SiO2/TiO2 and Fe3O4/SiO2/ZnO, with core/shell/shell structures were successfully prepared. In the first step, soft magnetic and hard magnetic Fe3O4 and SrFe12O19 powders were synthesized using carbon reduction and co-precipitation routes, respectively. In the second step, silica coating was performed by controlling the hydrolysis and con- densation of tetraethyl orthosilicate (TEOS) precursor on the magnetic cores. In the third step, a layer of TiO2 or ZnO photocatalytic shells was made on the as-prepared composites using titanium n-butoxide (TNBT) or zinc nitrate hexahydrate, respectively. The formation of the core/shell/shell structures was confirmed by FESEM and TEM analyses. The saturation magnetizations of the Fe3O4/SiO2/TiO2, SrFe12O19/SiO2/TiO2 and Fe3O4/SiO2/ZnO photocatalytic materials were 41.5, 33 and 49 emu/g, respectively. Photocatalytic activity was evaluated by degradation percentages of methylene blue (MB) under UV illumination, which were 88%, 83% and 62%, for the Fe3O4/SiO2/TiO2, SrFe12O19//TiO2 and Fe3O4/SiO2/ZnO composites, respectively. The first-, and second-order reaction kinetics were used to find out the suitable MB removal kinetics.