Concentration enrichment in confined, gradient energy systems

The enrichment or depletion of components near bounding surfaces in confined geometries was estimated using the generalized chemical potential for a molecule in a binary mixture. The chemical potential depends on concentration gradients and the local concentrations. Mean‐field–based parameter estima...

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Bibliographic Details
Published in:AIChE journal 2005-03, Vol.51 (3), p.1032-1041
Main Authors: Kosto II, Timothy J., Nauman, E. Bruce
Format: Article
Language:English
Subjects:
Applied sciences
Chemical engineering
Exact sciences and technology
Molecules
Thermodynamics
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Summary:The enrichment or depletion of components near bounding surfaces in confined geometries was estimated using the generalized chemical potential for a molecule in a binary mixture. The chemical potential depends on concentration gradients and the local concentrations. Mean‐field–based parameter estimates were combined with regular solution thermodynamics to calculate the enrichment of the favored component near an attractive bounding surface in confined geometries arising from weak van der Waals attractions. Partition coefficients from 2 to 3000 were calculated for pores of small but realistic diameter in contact with a reservoir of the binary mixture. Critical wetting transitions, like those reported for unconfined systems, occurred in confined pores. In such a transition, the material inside is near the upper binodal concentration when the reservoir concentration is below the lower binodal. The corresponding partition coefficient is then very large; appreciable concentration enrichment occurs even in pores that do not exhibit wetting transitions. © 2005 American Institute of Chemical Engineers AIChE J, 51: 1032–1041, 2005
ISSN:0001-1541
1547-5905
DOI:10.1002/aic.10422