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| Titel |
Characterization of nitrogen adsorption isotherms of thermally-treated organoclays using multifractal analysis |
| VerfasserIn |
Marcos Lado, Mikhail Borisover, Antonio Paz-González |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082322
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| Zusammenfassung |
| Nitrogen adsorption isotherms of soils have been reported to exhibit multifractal behavior. In
the present work, multifractal analysis is used to characterize changes in N2 adsorption
isotherms of organoclays prepared with different cations and exposed to various thermal
treatments. Wyoming bentonite was exchanged with benzyltrimethylammonium
(BTMA-clay), tetraethylammonium (TEA-clay), and hexadecyltrimethylammonium
exchanged at 41 and 90% of the cation exchange capacity of the clay (HDTMA41- and
HDTMA90-clay). The resulting organoclays were exposed to temperatures ranging from 25
to 420ºC during two hours, freeze-dried, and N2 adsorption isotherms were measured at
77ºK. The obtained isotherms showed multifractal behavior, and parameters derived from
Rényi and singularity spectra varied with changes in the organic cation and the treatment
temperature. The type of cation was the dominant factor responsible for changes in spectra,
and significant interactions were observed between type of cation and temperature for several
parameters. Significant correlations were found between organic carbon content and
multifractal parameters, indicating a relation between changes in N2 sorption sites and
thermal transformations of the organic cations. Significant correlations were also found
between some multifractal parameters and the heterogeneity exponent of a Freundlich
model fitted to nitrobenzene isotherms measured in the organoclays, suggesting that
multifractal analysis of N2 adsorption isotherms could be useful to analyze the
heterogeneity of sorption sites when sorption determinations yield a limited amount of data. |
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