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High internal phase CO2-in-water emulsions stabilized with a branched nonionic hydrocarbon surfactant.
MedLine Citation:
PMID:  16376919     Owner:  NLM     Status:  PubMed-not-MEDLINE    
A nonionic-methylated branched hydrocarbon surfactant, octa(ethylene glycol) 2,6,8-trimethyl-4-nonyl ether (5b-C12E8) emulsifies up to 90% CO2 in water with polyhedral cells smaller than 10 microm, as characterized by optical microscopy. The stability of these concentrated CO2/water (C/W) emulsions increases with pressure and in some cases exceeds 24 h. An increase in pressure weakens the attractive van der Waals interactions between the CO2 cells across water and raises the disjoining pressure. It also enhances the solution of the surfactant tail and drives the surfactant from water towards the water-CO2 interface, as characterized by the change in emulsion phase behavior and the decrease in interfacial tension (gamma) to 2.1 mN/m. As the surfactant adsorption increases, the greater tendency for ion adsorption is likely to increase the electrostatic repulsion in the thin lamellae and raise the disjoining pressure. As pressure increases, the increase in disjoining pressure and decrease in the capillary pressure (due to the decrease in gamma) each favor greater stability of the lamellae against rupture. The electrical conductivity is predicted successfully as a function of Bruggeman's model for concentrated emulsions. Significant differences in the stability are observed for concentrated C/W emulsions at elevated pressure versus air/W or C/W foams at atmospheric pressure.
Varun V Dhanuka; Jasper L Dickson; Won Ryoo; Keith P Johnston
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Publication Detail:
Type:  Journal Article     Date:  2005-12-27
Journal Detail:
Title:  Journal of colloid and interface science     Volume:  298     ISSN:  0021-9797     ISO Abbreviation:  J Colloid Interface Sci     Publication Date:  2006 Jun 
Date Detail:
Created Date:  2006-05-02     Completed Date:  2007-10-29     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0043125     Medline TA:  J Colloid Interface Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  406-18     Citation Subset:  -    
Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712, USA.
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