Preparation and photocatalytic performance of magnetic Fe3O4@TiO2 core–shell microspheres supported by silica aerogels from industrial fly ash

In this work, a ternary magnetic composite of Fe3O4@TiO2/SiO2 aerogel with good photocatalytic activity was prepared successfully by combining sol–gel and simple hydrothermal methods with Fe3O4@TiO2 core–shell microspheres and SiO2 aerogels from industrial fly ash as starting materials. The structural and magnetic features of the as-obtained Fe3O4@TiO2/SiO2 aerogel composite were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), N2 adsorption–desorption measurements, UV–vis diffuse reflectance spectra (UV–vis/DRS) and vibrating sample magnetometry (VSM). The results showed that Fe3O4@TiO2 core–shell microspheres were dispersed on the surface of SiO2 aerogels. The Fe3O4@TiO2/SiO2 aerogel composite material possessed excellent magnetic properties at room temperature, high adsorption capacity to organic pollutants, enhanced charge separation efficiency and strong light absorption in the visible region. The photocatalytic activity of the prepared Fe3O4@TiO2/SiO2 aerogel for Rhodamine B degradation under visible light irradiation was systematically investigated by varying the operational parameters such as pH value, catalyst concentration, irradiation time, and initial substrate concentration, etc. The photocatalytic reactions obeyed pseudo-first-order kinetics according to Langmuir–Hinshelwood model. The repeatability of photocatalytic activity was also tested. Compared to pure TiO2 and Fe3O4@TiO2 core–shell microspheres, the ternary composite of Fe3O4@TiO2/SiO2 aerogel showed higher photocatalytic activity for Rhodamine B degradation, which meant that this material can serve as an efficient and recyclable multifunctional photocatalyst for the degradation of hazardous organic dyes in wastewater.