title: Transport of oxidized multi-walled carbon nanotubes through silica based porous media: influences of aquatic chemistry, surface chemistry, and natural organic matter.
abstract: This paper provides results from studies of the transport of oxidized multi-walled carbon nanotubes (O-MWCNTs) of varying surface oxygen concentrations under a range of aquatic conditions and through uniform silica glass bead media. In the presence of Na(+), the required ionic strength (IS) for maximum particle attachment efficiency (i.e., the critical deposition concentration, or CDC) increased as the surface oxygen concentration of the O-MWCNTs or pH increased, following qualitative tenets of theories based on electrostatic interactions. In the presence of Ca(2+), CDC values were lower than those with Na(+) present, but were no longer sensitive to surface oxygen content, suggesting that Ca(2+) impacts the interactions between O-MWCNTs and glass beads by mechanisms other than electrostatic alone. The presence of Suwannee River natural organic matter (SRNOM) decreased the attachment efficiency of O-MWCNTs in the presence of either Na(+) or Ca(2+), but with more pronounced effects when Na(+) was present. Nevertheless, low concentrations of SRNOM (<4 mg/L of dissolved organic carbon) were sufficient to mobilize all O-MWCNTs studied at CaCl2 concentrations as high as 10 mM. Overall, this study reveals that NOM content, pH, and cation type show more importance than surface chemistry in affecting O-MWCNTs deposition during transport through silica-based porous media.
authors.affiliation: Department of Geography and Environmental Engineering, and ‡Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Jin
authors.initials: J
authors.lastname: Yang
authors.forename: Julie L
authors.initials: JL
authors.lastname: Bitter
authors.forename: Billy A
authors.initials: BA
authors.lastname: Smith
authors.forename: D Howard
authors.initials: DH
authors.lastname: Fairbrother
authors.forename: William P
authors.initials: WP
authors.lastname: Ball
mesh_terms: D006863:Hydrogen-Ion Concentration; D037742:Nanotubes, Carbon / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D037742:Nanotubes, Carbon; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D014867:Water; D012822:Silicon Dioxide; D010100:Oxygen