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| Titel |
Determination of interfacial parameters of a soluble particle in a nonideal solution from measured deliquescence and efflorescence humidities |
| VerfasserIn |
O. Hellmuth, A. K. Shchekin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 7 ; Nr. 15, no. 7 (2015-04-10), S.3851-3871 |
| Datensatznummer |
250119623
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| Publikation (Nr.) |
 copernicus.org/acp-15-3851-2015.pdf |
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| Zusammenfassung |
| In order to study the growth/shrinking of a hygroscopic nanoparticle during
hydration/dehydration in an atmosphere of water vapour, we have employed a
thermodynamic approach proposed by Shchekin et al. (2008). This approach uses
the mechanic and thermodynamic concept of disjoining pressure of thin films
and allows, among others, the prediction of the humidity growth factor of
both (i) a homogeneous solution droplet with completely dissolved residual
core and (ii) a heterogeneous solution droplet with partially dissolved
residual core as a function of the ambient relative humidity. For application
to a nanometric sodium chloride particle we have extended the original
approach by (i) considering the nonideality of the solution through the
dependence of molecular volumes of the solvent and solute molecules and the
solute and solvent activities on the solution concentration, (ii)
deriving an equation for the estimation of the efflorescence properties
of a homogeneous solution droplet, and (iii) combining the
empirical power law fittings for the size dependence of the deliquescence and
efflorescence relative humidity values by Biskos et al. (2006a). It was
demonstrated how the solution/solute interface energy and the correlation
length of a thin solution film can be determined from a combination of
experimentally determinable efflorescence and deliquescence humidities with
the present calculus. The solution/solute interface energy was found to be in
close agreement with some previous values reported in the literature, while
it strongly differs from data of some other sources. The calculated
deliquescence humidity shows a low sensitivity to the choice of the
numerical value for the film correlation length. The estimated film
correlation length of 1 nm for a nanometric sodium chloride particle with
dry particle radius of 5 nm was found to be reconcilable with available a
priori estimates of the correlation length from the literature when the
measurement uncertainty of the deliquescence humidity is considered.
Considering the combination of an extensive calculus, a comprehensive set of
thermophysical constraints, and independent measurements of the deliquescence
and efflorescence humidities as functions of dry particle radius, the
obtained values of the solution/solute interface energy and the correlation
length are in close agreement with previous estimations. The humidification
of sodium chloride particles in the initial hydration stages was found to be
very sensitive to the specification of the disjoining pressure. The
enhancement of the wettability of the particle surface leads to an earlier
onset of hygroscopic growth. |
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