Synthesis of Fe₂SiO₄-Fe₇Co₃ Nanocomposite Dispersed in the Mesoporous SBA-15: Application as Magnetically Separable...

The mixture containing alloy and oxide with iron-based phases has shown interesting properties compared to the isolated species and the synergy between the phases has shown positive effect on dye adsorption. This paper describes the synthesis of Fe₂SiO₄-Fe₇Co₃-based nanocomposite dispersed in Santa Barbara Amorphous (SBA)-15 and its application in dye adsorption followed by magnetic separation. Thus, it was studied the variation of reduction temperature and amount of hydrogen used in synthesis and the effect of these parameters on the physicochemical properties of the iron and cobalt based oxide/alloy mixture, as well as the methylene blue adsorption capacity. The XRD and Mössbauer results, along with the temperature-programmed reduction (TPR) profiles, confirmed the formation of Fe₂SiO₄-Fe₇Co₃-based nanocomposites. Low-angle XRD, N₂ isotherms, and TEM images show the formation of the SBA-15 based mesoporous support with a high surface area (640 m²/g). Adsorption tests confirmed that the material reduced at 700 °C using 2% of H₂ presented the highest adsorption capacity (49 mg/g). The nanocomposites can be easily separated from the dispersion by applying an external magnetic field. The interaction between the dye and the nanocomposite occurs mainly by π-π interactions and the mixture of the Fe₂SiO₄ and Fe₇Co₃ leads to a synergistic effect, which favor the adsorption.