Degradation of Methylene Blue by Ozone Oxidation Catalyzed by the Magnetic MnFe2O4@Co3S4 Nanocomposite

Abstract

In this study, the MnFe₂O₄@Co₃S₄ magnetic nanocomposite was prepared by a two-step hydrothermal method and used to catalyze the ozone oxidation degradation of methylene blue. It was characterized by XRD, EDS, SEM, FT-IR, and XPS. The results showed that the introduction of Co₃S₄ made MnFe₂O₄ grow uniformly on Co₃S₄ nanosheets, which effectively prevented the agglomeration of MnFe₂O₄. Moreover, MnFe₂O₄ provided active sites and Mn³⁺/Mn²⁺ and Fe³⁺/Fe²⁺ cycles for the ozone oxidation process. Not only did Co₃S₄ provide the active site (Co²⁺/Co³⁺) for the ozone oxidation process but also its derived S^2–/S₂^2– accelerated the electron transfer rate on the surface of the material, thus improving the efficiency of catalytic ozone oxidation degradation of methylene blue. When the molar ratio of MnFe₂O₄ to Co₃S₄ was 6:3 (MnFe₂O₄@Co₃S₄-3), the catalytic ozone degradation efficiency of methylene blue was the best, which reached 93.55% in 12 min. The reactive oxygen species in catalytic ozonation degradation of MB were ¹O₂, O₂^.–, and ·OH. The MnFe₂O₄@Co₃S₄ magnetic nanocomposite is an efficient and stable O₃ activator, which maintains high catalytic activity and low metal ion leaching after five cycles, indicating that it has a good application prospect in catalyzing ozone oxidation to degrade organic pollutants.