Study of thallium(III) adsorption onto multiwall carbon nanotubes

Multiwall carbon nanotubes (MWCNTs) oxidized by H2SO4, KMnO4, and HNO3 were used as sorbents and their sorption abilities for Tl(III) were compared with raw MWCNTs. The Langmuir model was used for the calculation of the amount of Tl(III) sorbed on the surface of MWCNTs. The acidic oxidation treatment of MWCNTs yielded a large number of functional groups, leading to a sharp increase in Tl(III) adsorption. Maximum adsorption of Tl(III) was recorded at a pH value of 7. The maximum amounts of Tl(III) sorbed on raw MWCNTs, H2SO4-oxidized, KMnO4-oxidized and HNO3-oxidized MWCNTs calculated by the Langmuir model were 3.0, 11.7, 21.6 and 31.5 mg/g, respectively. The MWCNTs oxidized by HNO3 showed the best sorption performance for Tl (III) ions.