Multifunctional sandwich-like mesoporous silica–Fe3O4–graphene oxide nanocomposites for removal of methylene blue from water

Abstract

Two multifunctional sandwich-like mesoporous silica–graphene oxide (GO@mSiO₂) and mesoporous silica–Fe₃O₄–graphene oxide (Fe₃O₄/GO@mSiO₂) adsorbents were synthesized, and the adsorption equilibrium and kinetics of methylene blue on both of them were investigated. The structural and physical properties of the adsorbents were investigated by transmission electron microscopy, X-ray diffraction, vibrating magnetometry, nitrogen adsorption–desorption measurement and their chemical properties were analyzed by X-ray photoelectron spectroscopy, infrared spectroscopy, and Raman spectroscopy. GO@mSiO₂ exhibited a high specific surface area of 634 m² g⁻¹ and its maximum adsorption capacity for methylene blue was 305.3 mg g⁻¹. The specific surface and the maximum adsorption capacity were 179 m² g⁻¹ and 125.1 mg g⁻¹ to Fe₃O₄/GO@mSiO₂, which could be recycled by using an external magnetic field because of its magnetic property. Moreover, both adsorbents exhibited photothermal properties. A second-order kinetic equation could best describe the adsorption kinetics. Thermodynamic parameters indicated that the adsorption of methylene blue onto both adsorbents was thermodynamically feasible and could occur spontaneously.