title: Influence of humic acids on sorption of alkanes by carbon nanotubes--implications for the dominant sorption mode.
abstract: The presence of humic substances (HS) has previously been shown to alter sorption properties of multi-walled carbon nanotubes (MWCNTs). To systematically study this process, three alkane pairs were selected as molecular probe sorbates. The influence of HS on sorption affinity, sorption linearity, and the dominant sorption mode (i.e., ad- or absorption) by MWCNTs was investigated. The addition of HS led to a continuous decrease in sorption affinity and an increase in sorption linearity with increasing HS addition. Furthermore, the comparison of distribution coefficients of n- and cycloalkanes showed that the dominant sorption mode remains to be adsorption regardless of the presence of HS on MWCNT surface. From this, it can be concluded that instead of a change in sorption mode to absorption of sorbates into HS-coated MWCNT, HS blocks high-energy sorption sites for subsequently added sorbates and that sorbates continuously sorb on the MWCNT surface.
authors.affiliation: Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstrasse 5, 45141 Essen, Germany; Centre for Water and Environmental Research (ZWU), University of Duisburg-Essen, Universitätsstrasse 2, 45141 Essen, Germany; Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria. Electronic address: thorsten.hueffer@univie.ac.at.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Hüffer
authors.affiliation: Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstrasse 5, 45141 Essen, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Schroth
authors.affiliation: Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstrasse 5, 45141 Essen, Germany; Centre for Water and Environmental Research (ZWU), University of Duisburg-Essen, Universitätsstrasse 2, 45141 Essen, Germany.
authors.forename: Torsten C
authors.initials: TC
authors.lastname: Schmidt
mesh_terms: D000327:Adsorption; D000473:Alkanes / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D008956:Models, Chemical; D015336:Molecular Probe Techniques; D037742:Nanotubes, Carbon / Q000737:chemistry*
chemical_list: D000473:Alkanes; D006812:Humic Substances; D037742:Nanotubes, Carbon
keywords: Adsorption vs. absorption; Carbon nanomaterials; Humic substances; Organic compounds