| In this work, the sorption features of bentonites with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as adsorbent for metal ions in water and can be subsequently removed from the medium by a simple magnetic process.The bentonite/iron oxide magnetic composites were prepared by co-precipitation method, and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), scanning electron microscope (SEM) and magnetization measurement. The results of characterizations indicated that the bentonite/iron oxide magnetic composites had a high magnetism and might form the iron oxide/bentonite covalent bonds.The prepared bentonite/iron oxide magnetic composites were used as a sorbent for the removal of Pb(Ⅱ), Ni(Ⅱ) and60Co(Ⅱ) ions from wastewater. The results demonstrated that the kinetic sorption of Pb(Ⅱ), Ni(Ⅱ) and60Co(Ⅱ) can be well described by the pseudo-second-order rate equation. The sorption of Pb(Ⅱ), Ni(Ⅱ) and60Co(Ⅱ) were strongly dependent on pH and ionic strength at low pH values. The sorption of Pb(Ⅱ), Ni(Ⅱ) and60Co(Ⅱ) were dominated by outer-sphere surface complexation or ion exchange at low pH, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The experimental datas were well described by Langmuir model. The thermodynamic parameters (⊿G0,⊿H0,⊿S0) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Pb(Ⅱ), Ni(Ⅱ) and60Co(Ⅱ) on bentonite/iron oxide magnetic composites were endothermic and spontaneous processes. The presence of iron oxide in the composites also contributed to the sorption of metal ions on the magnetic composites. The magnetic composites had a good reusability. These results suggest that the bentonite/iron oxide magnetic composites can be employed repeatedly in metal ions removal from aqueous solution in real work. |
PDF Full Text Request