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      Influence of surface oxygen on the interactions of carbon nanotubes with natural organic matter.

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          Abstract

          The sorption properties of natural organic matter (NOM) with oxidized multiwalled carbon nanotubes (O-MWCNTs) in simple electrolytes has been studied, as well as the effect that NOM concentration, pH, and O-MWCNT surface chemistry have on CNT stability under environmentally relevant conditions. As O-MWCNT oxygen content increased, NOM sorption decreased in simple electrolytes for a common set of solution conditions. For each O-MWCNT, NOM sorption increased with increasing ionic strength and decreasing pH, although the sensitivity of NOM sorption to these water quality parameters increased as the O-MWCNT oxygen content increased. Collectively, these observations indicate that NOM sorption by O-MWCNTs is determined by favorable hydrophobic π-π interactions that are moderated by repulsive electrostatic forces between negatively charged carboxylic acid functional groups on the O-MWCNTs and NOM. Stability studies conducted in artificial groundwater revealed that CNT stability is influenced by both the NOM concentration and pH, but stability was largely independent of the O-MWCNT oxygen concentration. These findings contrast with the marked effect that surface oxygen has on CNT stability in simple electrolytes. Electrophoretic mobility measurements revealed that the stabilizing effects of adsorbed NOM are due to the introduction of steric repulsion between NOM-coated CNTs, rather than from changes to surface charge.

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          Author and article information

          Journal
          Environ. Sci. Technol.
          Environmental science & technology
          American Chemical Society (ACS)
          1520-5851
          0013-936X
          Dec 04 2012
          : 46
          : 23
          Affiliations
          [1 ] Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
          Article
          10.1021/es303157r
          23145852
          80790811-8c12-483c-8ec5-17970f4d4e29
          History

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