Adsorption of hydroxyl- and amino-substituted aromatics to carbon nanotubes.
The combined effects of hydroxyl/amino functional groups of aromatics and surface O-containing groups of carbon nanotubes on adsorption were evaluated. When normalized for hydrophobicity, 2,4-dichlorophenol and 2-naphthol exhibited a greater adsorptive affinity to carbon nanotubes and graphite (a model adsorbent without the surface O functionality) than structurally similar 1,3-dichlorobenzene and naphthalene, respectively, and 1-naphthylamine exhibited a much greater adsorptive affinity than all other compounds. Results of the pH-dependency experiments further indicated that the hydroxy/amino functional groups of the adsorbates and the surface properties of the adsorbents played a combinational role in determining the significance of the nonhydrophobic adsorptive interactions. We propose that the strong adsorptive interaction between hydroxyl-substituted aromatics and carbon nanotubes/graphite was mainly due to the electron-donating effect of the hydroxyl group, which caused a strong electron-donor-acceptor (EDA) interaction between the adsorbates and the pi-electron-depleted regions on the graphene surfaces of carbon nanotubes or graphite. In addition to the EDA interaction, Lewis acid-base interaction was likely an extra important mechanism contributing to the strong adsorption of 1-naphthylamine, especially on the O-functionality-abundant carbon nanotubes. The findings of the present study might have significant implications for selective removal of environmental contaminants with carbon nanotubes.
College of Environmental Science and Engineering/Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300071, China.d State.
Wei
W
Chen
Lin
L
Duan
Lilin
L
Wang
Dongqiang
D
Zhu
D000327:Adsorption; D000588:Amines / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D037742:Nanotubes, Carbon / Q000737:chemistry*; D013696:Temperature
D000588:Amines; D006841:Hydrocarbons, Aromatic; D037742:Nanotubes, Carbon; D017665:Hydroxyl Radical