Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 47, Issue 24, Pages 14034-14043Publisher
AMER CHEMICAL SOC
DOI: 10.1021/es402448w
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Funding
- National Science Foundation [BES0731147]
- Environmental Protection Agency [RD-83385701-1]
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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 Ca2+, CDC values were lower than those with Na+ present, but were no longer sensitive to surface oxygen content, suggesting that Ca2+ 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 Ca2+, 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.
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