Concentration enrichment in confined, gradient energy systems

✍ Scribed by Timothy J. Kosto II; E. Bruce Nauman

• Publisher: American Institute of Chemical Engineers
• Year: 2005
• Tongue: English
• Weight: 251 KB
• Volume: 51
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.10422

✦ Synopsis

Abstract

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