Roles of interfacial properties on the stability of emulsified bitumen droplets.
Because of the deformable nature of emulsion droplets, it is imperative to consider the inter-droplet pressure in assessing the stability of a liquid-liquid dispersion. In a novel methodology, the pressure generated between droplets in axial compression is estimated through considerations of equilibrium shape mechanics. The applied compressive pressure is compared to the disjoining pressure, induced by the surface charges, resisting droplet-droplet interaction. The stability of bitumen droplets, emulsified in aqueous media, is assessed from surface mechanical and electrostatic perspectives. In support of the analysis, the tensions at, and zeta potentials near, the bitumen droplet surfaces are measured. The predicted trends of stability against coalescence are confirmed by novel droplet interaction experiments: Individual emulsified bitumen droplets, manipulated by suction micropipettes, are compressed against one another along a mutual axis at up to 100 nN force. The force is measured via the deflection of a sensitive microcantilever. Because of the statistical nature of the experimental observations, a probability of coalescence is quantified. The water chemistry dramatically influences bitumen droplet coalescence, which is enhanced in acidic environments and at high ionic strength.
Moran
Kevin
K
Syncrude Canada Ltd., Edmonton Research Centre, 9421-17 Avenue, Edmonton, Alberta, Canada. moran.kevin@syncrude.com