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| Titel |
Sorption of organic chemicals at biogeochemical interfaces - calorimetric measurements |
| VerfasserIn |
J. Krüger, F. Lang, J. Siemens, M. Kaupenjohann |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250028818
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| Zusammenfassung |
| Biogeochemical interfaces in soil act as sorbents for organic chemicals, thereby
controlling the degradation and mobility of these substances in terrestrial environments.
Physicochemical properties of the organic chemicals and the sorbent determine sorptive
interactions.
We hypothesize that the sorption of hydrophobic organic chemicals (“R-determined”
chemicals) is an entropy-driven partitioning process between the bulk aqueous phase and
biogeochemical interface and that the attachment of more polar organic chemicals
(“F-determined” chemicals) to mineral surfaces is due to electrostatic interactions and ligand
exchange involving functional groups.
In order to determine thermodynamic parameters of sorbate/sorbent interactions
calorimetric titration experiments have been conducted at 20Ë C using a Nanocalorimeter
(TAM III, Thermometric). Solutions of different organic substances (“R-determined”
chemicals: phenanthrene, bisphenol A, “F-determined” chemicals: MCPA, bentazone) with
concentrations of 100 μmol l-1 were added to suspensions of pure minerals (goethite,
muscovite, and kaolinite and to polygalacturonic acid (PGA) as model substance for biofilms
in soil. Specific surface, porosity, N and C content, particle size and point of zero charge of
the mineral were analyzed to characterize the sorbents.
The obtained heat quantities for the initial injection of the organic chemicals to
the goethite were 55 and 71 μJ for bisphenol A and phenanthrene (“R-determined
representatives”) and 92 and 105 μJ for MCPA and bentazone (“F-determined”
representatives). Further experiments with muscovite, kaolinite and PGA are in progress to
determine ÎGÂ and ÎHÂ of the adsorption process. |
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