High internal phase CO2-in-water emulsions stabilized with a branched nonionic hydrocarbon surfactant

TLDR: The electrical conductivity is predicted successfully as a function of Bruggeman's model for concentrated emulsions at elevated pressure versus air/W or C/W foams at atmospheric pressure.

Abstract: A nonionic-methylated branched hydrocarbon surfactant, octa(ethylene glycol) 2,6,8-trimethyl-4-nonyl ether ( 5b -C 12 E 8 ) emulsifies up to 90% CO 2 in water with polyhedral cells smaller than 10 μm, as characterized by optical microscopy The stability of these concentrated CO 2 /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 CO 2 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–CO 2 interface, as characterized by the change in emulsion phase behavior and the decrease in interfacial tension ( γ ) to 21 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 γ ) 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