Phase transitions of adsorbates. V. Aqueous sodium chloride solutions adsorbed of porous silica glass

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AuthorSearch for:
TypeArticle
Journal titleJournal of Colloid and Interface Science
ISSN0021-9797
Volume45
Issue1
Pages154169; # of pages: 16
Subjectadsorption; phase transformation; silica glass; sodium chloride; Concrete
AbstractAdsorption isotherms for water on porous silica glass containing various amounts of NaCl, determined at room temperature, can be superimposed if salt exclusion in the first monolayer and relative pressure values based on existing salt concentration are assumed. The changes in dimensions and heat content of the same glass specimens fully saturated with water were deterimined in nonequilibrium temperature cycles between +5 and -80 degrees C. The results are explicable by the hypothesis that peculiarities result from the difference between the vapor pressure of the liquid-like adsorbate and that of the solid in the surroundings. No phase separation in the originally occupied pores was detected, but solidification of the solution after redistribution proceeded in a way similar to that of bulk two-component systems. Observations following first freezing were in full harmony with those for the salt- free system. Two aspects of the second freezing, however, were unlike the previously studied case: the magnitude of expansion on cooling was larger at slow rates than at rapid rates and expansion instead of contraction occurred on warming. Low vapor pressure, high viscosity and the presence of some ice in the larger pores are assumed to be the source of these anomalies. Results obtained with aqueous glycerine solutions as adsorbate appear to support this view.
Publication date
LanguageEnglish
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedNo
IdentifierDBR-RP-571
NRC number13437
2695
NPARC number20374670
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Record identifierb49fba09-4700-471a-a188-e371e519e522
Record created2012-07-23
Record modified2016-05-09
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