Preparation of Fe3O4@SiO2@N-TiO2 and Its Application for Photocatalytic Degradation of Methyl Orange in Na2SO4 Solution

In this paper, Fe3O4@SiO2@TiO2 and N-doped Fe3O4@SiO2@N-TiO2 photocatalysts with magnetic core-shell structures were prepared using a multi-step synthesis method. The materials were analyzed using various techniques, such as X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), selected-area electron diffraction patterns (SAED), and X-ray photoelectron spectroscopy (XPS). The results indicated that the prepared samples had an anatase structure, and N was successfully doped. Fe3O4@SiO2@TiO2 and Fe3O4@SiO2@N-TiO2 with different amounts of nitrogen doping were used for the study of photocatalytic degradation of methyl orange (MO) in pure MO solution, and in MO and Na2SO4 (MO-Na2SO4) mixed solution, respectively. The average photocatalytic degradation rate of MO in pure MO solution with three different batches each of Fe3O4@SiO2@TiO2 and Fe3O4@SiO2@N-TiO2 (3 mL of NH4OH used for doping) under high-pressure mercury lamp irradiation reached 85.25% +/- 2.23% and 95.53% +/- 0.53%, respectively. The average photocatalytic degradation rate of MO in the MO-Na2SO4 mixed solution with three different batches each of Fe3O4@SiO2@TiO2 and Fe3O4@SiO2@N-TiO2 (3 mL of NH4OH used for doping) under the same irradiation condition reached 90.46% +/- 3.33% and 97.79% +/- 2.09%, respectively. The results showed that Na2SO4 can promote photocatalytic degradation of MO. The experiment of recycling photocatalysts showed that there was still a good degradation effect after five cycles. Finally, the first-order kinetic model and the photocatalytic degradation mechanism were investigated.