title: Adsorption of lead(II) on O₂-plasma-oxidized multiwalled carbon nanotubes: thermodynamics, kinetics, and desorption.
abstract: O(2)-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(2)-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 (ΔH°, ΔS°, and ΔG°) 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.
authors.affiliation: Research Center for Biomimetic Functional Materials and Sensing Devices, Institute of Intelligent Machines, Chinese Academy of Sciences , Hefei, Anhui 230031, People's Republic of China.
authors.forename: Xin-Yao
authors.initials: XY
authors.lastname: Yu
authors.forename: Tao
authors.initials: T
authors.lastname: Luo
authors.forename: Yong-Xing
authors.initials: YX
authors.lastname: Zhang
authors.forename: Yong
authors.initials: Y
authors.lastname: Jia
authors.forename: Bang-Jing
authors.initials: BJ
authors.lastname: Zhu
authors.forename: Xu-Cheng
authors.initials: XC
authors.lastname: Fu
authors.forename: Jin-Huai
authors.initials: JH
authors.lastname: Liu
authors.forename: Xing-Jiu
authors.initials: XJ
authors.lastname: Huang
mesh_terms: D000327:Adsorption; D007700:Kinetics; D007854:Lead / Q000737:chemistry*; D008854:Microscopy, Electron; D037742:Nanotubes, Carbon; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D037742:Nanotubes, Carbon; D007854:Lead; D010100:Oxygen