Preparation of CoFe2O4@vacancy@mSiO2 core-shell composites for removal of organic pollutant in aqueous solution

Abstract

CoFe2O4@vacancy@mSiO2 magnetic composites with core-shell structure were prepared with a simple two-step route and used for removal of organic pollutant in aqueous solution. The as-prepared nanocomposites were characterized by Brunner−Emmet−Teller (BET) measurements, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometer (VSM). The adsorption performances of CoFe2O4@vacancy@mSiO2 for Rhodamine B (RhB) were evaluated. The effects of initial dye concentration, adsorbent dosage, contact time, solution pH, temperature, ionic strength on dye adsorption were studied. Finally, four consecutive adsorption–desorption cycles were conducted to investigate the reusability of CoFe2O4@vacancy@mSiO2. The results showed that CoFe2O4@vacancy@mSiO2 could remove RhB in a wide pH range. Increasing ionic strength could enhance the adsorption capacity of CoFe2O4@vacancy@mSiO2 for RhB. The adsorption equilibrium obeyed Freundlich isotherm model and the maximum adsorption capacity under optimal conditions could reach 172.34 mg/g. The adsorption process of RhB onto CoFe2O4@vacancy@mSiO2 nanocomposites was very fast and kinetic process could be represented by pseudo-second-order kinetic model. Thermodynamic parameters suggested that the adsorption of RhB onto CoFe2O4@vacancy@mSiO2 was spontaneous and exothermic in nature. Based on the above results, the synthesized CoFe2O4@vacancy@mSiO2 could be used as an effective adsorbent for RhB removal.