Wei Zhang - Aggregation Kinetics and Transport of Single-Walled Carbon Nanotubes at Low Surfactant Concentrations

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  Publication Details (including relevant citation   information): Bouchard, Dermont, Zhang, Wei, Powell,   Tremaine, Rattanaudompol, U-sa, Environ. Sci. Technol.,   2012, 46 (8), pp 4458-4465

  Abstract: Little is known about how low levels   of surfactants can affect the colloidal stability of   single-walled carbon nanotubes (SWNTs) and how   surfactant-wrapping of SWNTs can impact ecological exposures in   aqueous systems. In this study, SWNTs were suspended in water   with sodium dodecylsulfate (SDS) as a surface-active dispersing   agent. The effect of SDS concentration on SWNT suspension   stability was investigated with time-resolved dynamic light   scattering (TRDLS) initial aggregation studies utilizing both   monovalent (Na+) and divalent (Ca2+) cations. The critical   coagulation concentration (CCC) values increased with SDS   concentration for the Na+ treatments, but the Ca2+ treatments   were less sensitive to SDS concentration changes. Longer term   stability studies with SDS concentrations orders of magnitude   below the SDS critical micelle concentration demonstrated that   SWNTs remained suspended for over six weeks in a surface water.   Transport studies in a freshwater sediment similarly showed a SDS   concentration-dependent mobility of SDS?wrapped SWNTs in that   SWNTs showed a relatively greater retention at lower SDS   concentrations (0.001%?0.05% w/v) than at a higher SDS   concentration (0.1%). It is hypothesized that the stability and   mobility of SWNT suspensions is directly related to the surface   coverage of SDS on the SWNT surface that simultaneously increases   electrosteric repulsion and decreases surface chemical   heterogeneity. Overall, these studies demonstrate that low levels   of surfactant are effective in stabilizing and mobilizing SWNTs   in environmental media.

  Address (URL): http://dx.doi.org/10.1021/es204618v