title: Adsorption of phenanthrene, 2-naphthol, and 1-naphthylamine to colloidal oxidized multiwalled carbon nanotubes: effects of humic acid and surfactant modification.
abstract: Carbon nanotubes (CNTs) can exist in the form of colloidal suspension in aquatic environments, particularly in the presence of natural organic matter or surfactants, and may significantly affect the fate and transport of organic contaminants. In the present study, the authors examined the adsorption of phenanthrene, 2-naphthol, and 1-naphthylamine to three colloidal CNTs, including a stable suspension of oxidized multiwalled carbon nanotubes (O-MWNT), a humic acid (HA)-modified colloidal O-MWNT, and a sodium dodecyl sulfate (SDS)-modified colloidal O-MWNT. All three colloidal O-MWNTs exhibit strong adsorption affinities to the three test compounds (with K(OC) values orders of magnitude greater than those of natural organic matter), likely resulting from strong nonhydrophobic interactions such as π-π electron donor-acceptor interactions and Lewis acid-base interactions. When thoroughly mixed, HA (at ∼310 mg HA/g CNT) and SDS (at ∼750 mg SDS/g CNT) significantly affected the aggregation properties of O-MWNT, causing individually dispersed tubes to form a loosely entangled network. The effects of HA or SDS modification on adsorption are twofold. Adsorption of HA/SDS significantly reduces surface areas of O-MWNT; however, the entangled network allows adsorbate molecules to interact simultaneously with multiple tubes. An important implication is that humic substances and surfactant-like materials not only facilitate the formation of colloidal carbon nanoparticles but also affect how these colloidal carbon nanoparticles adsorb organic contaminants.
authors.affiliation: College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin, PR China.
authors.forename: Lei
authors.initials: L
authors.lastname: Hou
authors.forename: Dongqiang
authors.initials: D
authors.lastname: Zhu
authors.forename: Ximeng
authors.initials: X
authors.lastname: Wang
authors.forename: Lilin
authors.initials: L
authors.lastname: Wang
authors.forename: Chengdong
authors.initials: C
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
mesh_terms: D015057:1-Naphthylamine / Q000032:analysis / Q000737:chemistry*; D000327:Adsorption; D006812:Humic Substances; D008956:Models, Chemical; D037742:Nanotubes, Carbon / Q000737:chemistry*; D009284:Naphthols / Q000032:analysis / Q000737:chemistry*; D010616:Phenanthrenes / Q000032:analysis / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D006812:Humic Substances; D037742:Nanotubes, Carbon; D009284:Naphthols; D010616:Phenanthrenes; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D012967:Sodium Dodecyl Sulfate; C031181:phenanthrene; D015057:1-Naphthylamine; C028405:2-naphthol