Adsorption of U(VI) on nonthermal plasma-modified carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) grafted O-phosphoethanolamine (O-PEA) were prepared by nonthermal plasma technology for U(VI) adsorption. The modified MWCNTs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD) and Raman spectra. The static adsorption study was carried out and the parameter effect on the adsorption capacity including contact time, pH, ionic strength and temperature were investigated. The results indicate that U(VI) adsorption on MWCNTs (PTMWCNTs-4) is the best, about three times that of the raw MWCNTs. The modified MWCNTs have a faster adsorption rate. The adsorption of U(VI) on PTMWCNTs-4 is dominated by the innersphere surface complexation at pH<7.0, whereas by the outer-sphere surface complexation or ion exchange at pH>7.0. Thermodynamic data show that the adsorption process is an exothermic and spontaneous process. This work provides a new environmental modification method for the efficient removal of U(VI).