Synthesis of Porous Fe3O4 Nanospheres and Its Application for the Catalytic Degradation of Xylenol Orange

Porous magnetite (Fe 3 O 4 ) nanospheres composed of primary nanocrystals have been successfully synthesized by solvothermal method with FeCl 3 ·6H 2 O serving as the single iron resource, polyvinylpyrrolidone (PVP) as the capping agent, and sodium acetate as the precipitation agent. To understand the formation mechanism of the porous Fe 3 O 4 nanospheres, the reaction conditions such as the concentration of the precursor, capping agent, precipitation agent, the reaction temperature, and reaction time were investigated. The characterization of the as-prepared product was identified with transmission electronic microscopy (TEM), field emission scanning electronic microscopy (FE-SEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), N 2 adsorption–desorption technique, and Fourier transform infrared spectroscopy (FTIR). The results indicate that the porous Fe 3 O 4 nanospheres display excellent magnetic properties at room temperature, which allows them to be easily separated from the reaction system with the help of external magnet when they serve as catalysts. Catalytic activity studies show that the as-prepared porous Fe 3 O 4 nanospheres are highly effective catalysts for the degradation of xylenol orange (XO) in aqueous solution with H 2 O 2 as oxidant. The degradation reaction is first-order, its rate constant at room temperature being 0.056 min –1 . Furthermore, the catalytic activity of Fe 3 O 4 nanospheres decreases very slightly after seven cycles of the catalysis experiment. Therefore, porous Fe 3 O 4 nanospheres can serve as effective recyclable catalysts for the degradation of XO.