Linear β‑Cyclodextrin Polymer Functionalized Multiwalled Carbon Nanotubes as Nanoadsorbent for Highly Effective Removal of U(VI) from Aqueous Solution Based on Inner-Sphere Surface Complexation

Linear β-cyclodextrin polymer functionalized multiwalled carbon nanotubes (MWCNTs-CDP) were synthesized and employed as a novel nanoadsorbent to remove uranyl ions in wastewater solutions. The characterization of MWCNTs-CDP, with Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET), suggested that the CDP was successfully modified on the MWCNTs surfaces. The removal efficiency of uranyl ions in aqueous solution by MWCNTs-CDP was investigated via varying various experimental conditions. We found that the removal of uranyl ions correlated with both pH and temperature, and the optimum pH and temperature were 6.0 and 323.15 K, respectively. The adsorption of uranyl ions was very fleet at the initial 1 h and then reached the adsorption equilibrium after 3 h. The data from the adsorption dynamics experiment could be commendably fitted by the pseudo-second-order model (R2 > 0.982), suggesting that chemisorption might be the rate-controlling mechanism. The Langmuir model (R2 > 0.995) manifested that the maximum adsorption capacity of uranyl ions on MWCNTs-CDP was boosted from 66.16 to 89.54 mg g–1 upon the change of temperature from 293.15 to 323.15 K. This result was better than that of some reported adsorbents. The thermodynamics analysis proved that the adsorption of uranyl ions on MWCNTs-CDP was a spontaneous process and an endothermic one. The adsorption mechanism of uranyl ions on MWCNTs-CDP was verified to be dominated by inner-sphere surface complexation. Our results indicated that MWCNTs-CDP can be utilized as a novel nanoadsorbent for highly effective removal of uranyl ions in actual uranyl-bearing effluents