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Influence of the initial state of carbon nanotubes on their colloidal stability under natural conditions |
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| Authors: | Schwyzer Irène Kaegi Ralf Sigg Laura Magrez Arnaud Nowack Bernd |
| Institution: | a Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-9014 St. Gallen, Switzerland b Eawag - Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland c EPFL - Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland |
| Abstract: | The colloidal stability of dry and suspended carbon nanotubes (CNTs) in the presence of amphiphilic compounds (i.e. natural organic matter or surfactants) at environmentally realistic concentrations was investigated over several days. The suspensions were analyzed for CNT concentration (UV-vis spectroscopy), particle size (nanoparticle tracking analysis), and CNT length and dispersion quality (TEM). When added in dry form, around 1% of the added CNTs remained suspended. Pre-dispersion in organic solvent or anionic detergent stabilized up to 65% of the added CNTs after 20 days of mild shaking and 5 days of settling. The initial state of the CNTs (dry vs. suspended) and the medium composition hence are critical determinants for the partitioning of CNTs between sediment and the water column. TEM analysis revealed that single suspended CNTs were present in all suspensions and that shaking and settling resulted in a fractionation of the CNTs with shorter CNTs remaining predominantly in suspension. |
| Keywords: | Carbon nanotubes Surfactants (anionic non-ionic cationic) Natural organic matter (humic/fulvic acid) Long-term colloidal stability |
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