Removal of methylene blue and mechanism on magnetic γ-Fe2O3/SiO2 nanocomposite from aqueous solution

• Core–shell magnetic γ-Fe2O3/SiO2 (M-γFS) was synthesized and characterized.
• M-γFS exhibited high adsorption capacity for removing methylene blue (MB) from water.
• The effect of different parameters on the adsorption were investigated in detail.
• The mechanism was systematically discussed and proposed with kinetics, isotherms and thermodynamics.
• The regenerated M-γFS was successfully reused four times.

Magnetic γ-Fe2O3/SiO2 (M-γFS) nanocomposite was prepared using γ-Fe2O3 as the magnetic carriers. M-γFS was characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), and Fourier Transform infrared spectroscopy (FTIR). The characterizations of M-γFS exhibit the irregular core-shell structure, and SiO2 has been successfully coated on the surface of γ-Fe2O3. M-γFS has much higher adsorption capacity 116.09 mg/g calculated by coated SiO2 on M-γFS than γ-Fe2O3 and SiO2, and the alkaline conditions are beneficial to the adsorption of MB. Coexisting cations, ionic strength and humic acid can influence the adsorption capacity. Meanwhile, adsorption kinetics data for M-γFS show good fit to the pseudo-second-order kinetics model, and the Langmuir equation is more appropriate to describe the adsorption behavior of MB on M-γFS. Moreover, after recycling four times, M-γFS washed by ethanol can still keep high adsorption capacity for MB adsorption.

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