How water adsorbs in hydrophobic nanospaces

Nguyen, Thanh X. and Bhatia, Suresh K. (2011) How water adsorbs in hydrophobic nanospaces. The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces, 115 33: 16606-16612. doi:10.1021/jp2053162


Author Nguyen, Thanh X.
Bhatia, Suresh K.
Title How water adsorbs in hydrophobic nanospaces
Journal name The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces   Check publisher's open access policy
ISSN 1932-7447
1932-7455
Publication date 2011-08-25
Sub-type Article (original research)
DOI 10.1021/jp2053162
Volume 115
Issue 33
Start page 16606
End page 16612
Total pages 7
Place of publication Washington, DC, U.S.A.
Publisher American Chemical Society
Collection year 2012
Language eng
Formatted abstract
The entry of water into hydrophobic nanospaces is critical to a variety of biological processes and in nanotechnologies for desalination and separation by nanofluidic devices. Idealized models of hydrophobic carbons have hitherto been used in simulations to investigate the anomalous adsorption of water, but the answer to the difficult question of how water enters such spaces has remained elusive. Here we show that while water entry does not occur in idealized independent carbon slit pores it is observed in realistic models of carbons having connected pore spaces. Good agreement with experimental water adsorption data is obtained for a realistic atomistic model of a disordered hydrophobic activated carbon fiber. Upon analyzing the adsorption in this atomistic model, and in another comprising adjacent slit pores connected by a small window in the separating wall, we find that the critical factor governing the behavior is the formation of sufficiently large and stable water clusters at windows or nanospaces connecting small and large pores. When this window size is large enough for the formation of a stable water cluster, condensation in a small pore induces the filling of empty large connected pores. This unique feature is not observed for nonpolar or weak polar gases (e.g., Ar or N2) at subcritical conditions and explains why the Kelvin equation fails to estimate the condensation pressure for water.
Keyword Graphitized carbon-black
Monte-carlo-simulation
Activated carbons
Adsorption-isotherms
Liquid water
Vapor
Nanopores
Micropores
Nanotubes
Mesopores
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
Official 2012 Collection
 
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