Organo-functionalization For Magnetic Chrysotile Nanotubes And Their Adsorption For Heavy Metal Ions

In this work, magnetic chrysotile nanotubes with mercapto group (MChNTs-SH) were prepared. The morphology structure and magnetic properties of MChNTs-SH were primarily studied. After that, the adsorption properties of Cd(II), Cu(II) and Co(II) on MChNTs-SH were investigated and the adsorption mechanism was evaluated.MChNTs-SH were characterized by SEM, TEM, XRD, FTIR, N2 adsorption-desorption isotherms, XPS and VSM. The characterization results showed that the prepared samples had hollow structure and inner-diameter and outer-diameter were respectively 5-15 nm and 15-50 nm. VSM measurement showed that the saturation magnetization of MChNTs and MChNTs-SH were 14.14 emu/g and 14.08 emu/g, which showed that mercapto modification process did not reduce the magnetic strength of MChNTs. Materials could be quickly separated from aqueous solutions by a permanent magnet.The adsorption properties of Cd(II), Cu(II) and Co(II) on MChNTs-SH were studied by static sorption method. The effects of contact time, pH, solid content, and temperature on Cd(II), Cu(II) and Co(II) adsorption to MChNTs-SH were investigated. According to the experimental results, the conclusions were as followed:(1) The adsorption kinetics of MChNTs-SH for Cd(II), Cu(II) and Co(II) were fitted better by the pseudo-second-order model than pseudo-first-order model; (2) pH affected the adsorption of Cd(II), Cu(II) and Co(II) on MChNTs-SH obviously. At low pH, adsorption rate was low. With pH increasing, removal rate increased gradually and reached 100%; The adsorption mechanism was as followed:At low pH, it could be explained as ion exchange and outer-sphere surface complexation, whereas surface precipitation was the main adsorption mechanism at high pH. (3) The Langmuir and Freundlich models were applied to simulate the sorption isotherms, and the results showed that the Langmuir model fitted the experimental data of Cd(II), Cu(II) and Co(II) better than the Freundlich model, and the maximal adsorption capacity of Cd(II), Cu(II) and Co(Ⅱ) on MChNTs-SH were respectively 33.98,34.93,13.36 mg/g; (4) The adsorption process of Cd(II), Cu(II) and Co(II) on MChNTs-SH is spontaneous and endothermic; (5) The adsorption performance of MChNTs-SH were better than MChNTs obviously; (6) The MChNTs-SH adsorbing Cd(II), Cu(II) and Co(II) had a selective adsorption, and the order was Co(II)>Cu(Ⅱ)>Cd(II); (7) Comparing with other adsorbents, the prepared MChNTs-SH showed better adsorption capacity and excellent regeneration property, and it could be easily separated from aqueous solutions using a magnetic separation method.