Sorption of radiocobalt(II) onto MWCNTs: effects of solid content, contact time, pH, ionic strength, humic acid and temperature

Multiwalled carbon nanotubes (MWCNTs) have attracted intense multidisciplinary study because of their special physicochemical properties. In this paper, the effect of solid content, contact time, pH, temperature and humic acid on radionuclide (⁶⁰Co(II)) on MWCNTs was studied by using batch technique. The results indicate that the sorption of Co(II) on MWCNTs can achieve sorption equilibration in short time and the kinetic sorption can be described by pseudo-second-order model well. The sorption of Co(II) on MWCNTs is strongly dependent on pH and independent of ionic strength, suggesting that the sorption of Co(II) on MWCNTs is mainly dominated by inner-sphere surface complexation rather than by outer-sphere surface complexation or ion exchange. The thermodynamic parameters calculated from the temperature-dependent sorption isotherms indicate that the sorption of Co(II) on MWCNTs was an endothermic and spontaneous process. The results of high sorption capacity of Co(II) suggest that MWCNTs can be used as efficient materials for the preconcentration of radiocobalt from large volumes of aqueous solutions in radionuclide polluted water.