10.1021/am2004202.s001 Xin-Yao Yu Xin-Yao Yu Tao Luo Tao Luo Yong-Xing Zhang Yong-Xing Zhang Yong Jia Yong Jia Bang-Jing Zhu Bang-Jing Zhu Xu-Cheng Fu Xu-Cheng Fu Jin-Huai Liu Jin-Huai Liu Xing-Jiu Huang Xing-Jiu Huang Adsorption of Lead(II) on O<sub>2</sub>-Plasma-Oxidized Multiwalled Carbon Nanotubes: Thermodynamics, Kinetics, and Desorption American Chemical Society 2011 Raman spectroscopy measurements show Scanning electron microscopy MWCNT Langmuir isotherm model transmission electron microscopy adsorption pH values 2011-07-27 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Adsorption_of_Lead_II_on_O_sub_2_sub_Plasma_Oxidized_Multiwalled_Carbon_Nanotubes_Thermodynamics_Kinetics_and_Desorption/2628184 O<sub>2</sub>-plasma-oxidized multiwalled carbon nanotubes (po-MWCNTs) have been used as an adsorbent for adsorption of lead(II) in water. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy measurements show that the bulk properties of MWCNTs were not changed after O<sub>2</sub>-plasma oxidation. The adsorption capacity of MWCNTs for lead(II) was greatly enhanced after plasma oxidation mainly because of the introduction of oxygen-containing functional groups onto the surface of MWCNTs. The removal of lead(II) by po-MWCNTs occurs rather quickly, and the adsorption kinetics can be well described by the pseudo-second-order model. The adsorption isotherm of lead(II) onto MWCNTs fits the Langmuir isotherm model. The adsorption of lead(II) onto MWCNTs is strongly dependent upon the pH values. X-ray photoelectron spectroscopy analysis shows that the adsorption mechanism is mainly due to the chemical interaction between lead(II) and the surface functional groups of po-MWCNTs. The thermodynamic parameters (Δ<i>H</i>°, Δ<i>S</i>°, and Δ<i>G</i>°) calculated from the adsorption isotherms suggest that the adsorption of lead(II) onto MWCNTs is endothermic and spontaneous. The regeneration performance shows that lead(II) can be easily regenerated from po-MWCNTs by altering the pH values of the solution.