Enhanced visible-light photocatalytic activity and recyclability of magnetic core-shell Fe3O4@SiO2@BiFeO3–sepiolite microspheres for organic pollutants degradation

Abstract

Novel magnetic core-shell structured Fe3O4@SiO2@BiFeO3–sepiolite microspheres were fabricated via a facile hydrothermal method. The as-prepared microspheres comprised a Fe3O4@SiO2 magnetic core with a strong response to external fields and a porous BiFeO3/sepiolite composite functional layer. The specific surface area, magnetization saturation value (Ms), and band gap energy (Eg) of Fe3O4@SiO2@BiFeO3–sepiolite (x = 0.4 g) were 126.68 m2/g, 18.2 emu/g, and 2.09 eV, respectively. A suitable amount of sepiolite in Fe3O4@SiO2@BiFeO3–sepiolite could improve the microstructure of the photocatalyst through the interface effect between the sepiolite and the formed BiFeO3, which can enlarge the specific surface area and thus increase the absorption of light and the adsorption of pollutants, decrease the Eg of the as-prepared photocatalyst, and improve the separation and inhibit the recombination of photogenic electron and hole (e−/h+) pairs, thereby expediting the photocatalytic degradation of pollutants. The as-obtained Fe3O4@SiO2@BiFeO3–sepiolite (x = 0.4 g) exhibited a remarkable photocatalytic degradation performance for ciprofloxacin (CIP), tetracycline hydrochloride (TC-H), and methylene blue (MB) and an excellent decolorization for the mixed solution of methyl orange (MO), rhodamine B (Rh B), and MB under visible-light irradiation. In addition, the as-obtained photocatalyst demonstrated excellent magnetic separation performance, recyclability, and stability. The active species produced during the photocatalysis included OH, O2−, and h+, with OH being the dominant active species. Such a well-structured core-shell photocatalyst has remarkable potential for numerous applications in treating organic wastewater.