Adsorption of phosphate ions from aqueous solutions by a CeO2 functionalized Fe3O4@SiO2 core-shell magnetic nanomaterial.

Phosphate is generally considered to be one of the nutrients for plants which may cause eutrophication of the aquatic environment. In this study, a CeO2-functionalized Fe3O4@SiO2 core-shell magnetic nanomaterial (denoted as Fe3O4@SiO2-CeO2) was prepared and used as the adsorbent to remove phosphate from water. The adsorbents were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption/desorption isotherms. Characterization results show that the particle size is around 8.63 nm, Brunauer-Emmett-Teller (BET) surface area is 179.7 m2 · g-1 and the pore volume is 0.39 cm3 · g-1 for magnetite Fe3O4@SiO2-CeO2. The adsorbents could be rapidly separated under an external magnetic field. Batch adsorption tests show that the Fe3O4@SiO2-CeO2 adsorbent exhibited high adsorption affinity for phosphate. Additionally, phosphate adsorption isotherms over the adsorbents could be well described by the Langmuir model, suggesting monolayer adsorption, and phosphate adsorption kinetics followed the pseudo-second-order kinetics. Moreover, increasing pH led to suppressed phosphate adsorption, and phosphate adsorption slightly increased with ionic strength.