title: Catalytic effects of functionalized carbon nanotubes on dehydrochlorination of 1,1,2,2-tetrachloroethane.
abstract: The environmental implications of carbon nanomaterials have received much attention. Nonetheless, little is known about how carbon nanomaterials might affect the abiotic transformation of organic contaminants in aquatic environments. In this study, we observed that three functionalized multiwalled carbon nanotubes (MWCNTs)-including a hydroxylated MWCNT (OH-MWCNT), a carboxylated MWCNT (COOH-MWCNT), and an aminated MWCNT (NH2-MWCNT)-all had strong catalytic effects on the dehydrochlorination of 1,1,2,2-tetrachloroethane (TeCA) at three different pH (7, 8, and 9); notably, the most significant effects (up to 130% increase in reaction rate) were observed at pH 7, at which reaction kinetics was very slow in the absence of MWCNT. The primary mechanism was that the -NH2 group and the deprotonated -COOH and -OH groups serve as bases to catalyze the reaction. Modeling results indicate that at any given pH the transformation kinetic constants of MWCNT-adsorbed TeCA were up to 2 orders of magnitude greater than the respective kinetic constant of dissolved TeCA. The overall catalytic effects of the MWCNTs depended both on the basicity of the surface functionalities of MWCNT and on the adsorption affinities of MWCNT for TeCA. Interestingly, Suwannee River humic acid-selected as a model dissolved organic matter-had negligible effects on the dehydrochlorination kinetics, even though it is rich in surface O-functionalities. An important environmental implication is that carbon nanotubes released into the environment might significantly affect the fate of chlorinated solvents.
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 300071, China.
authors.forename: Weifeng
authors.initials: W
authors.lastname: Chen
authors.forename: Dongqiang
authors.initials: D
authors.lastname: Zhu
authors.forename: Shourong
authors.initials: S
authors.lastname: Zheng
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D002384:Catalysis; D004980:Ethane / Q000031:analogs & derivatives* / Q000737:chemistry; D054879:Halogenation; D006812:Humic Substances / Q000032:analysis; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D037742:Nanotubes, Carbon / Q000737:chemistry*; D045483:Rivers / Q000737:chemistry; D012995:Solubility; D012996:Solutions; D013499:Surface Properties; D013696:Temperature
chemical_list: D006812:Humic Substances; D006843:Hydrocarbons, Chlorinated; D037742:Nanotubes, Carbon; D012996:Solutions; C015530:1,1,2,2-tetrachloroethane; D004980:Ethane