PHASE INVERSION OF A SOLID-STABILIZED EMULSION: EFFECT OF PARTICLE CONCENTRATION

Tiny water droplets in oil emulsions are commonly encountered in the petroleum industry. The high viscosity of the oil hampers the physical separation of the water droplets from the oil.(1) Phase inversion could be a potential workaround for this problem by making water, a much less viscous phase, the continuous medium. In the present work, we focused on triggering phase inversion of a solid-stabilized emulsion. We induced a catastrophic phase inversion by the continuous addition of a dispersed phase. The evolution of droplet morphology during the phase inversion process was observed and was measured in-line using a particle vision microscope, which proved to be a powerful tool for monitoring this rapid, unstable process. A linear relationship between the droplet size and the dispersed phase volume fraction before the phase inversion was observed, indicating that a higher dispersed phase volume fraction was needed for the phase inversion to occur with higher particle concentrations. The phase inversion conditions were applied in a regime where the particles were insufficient to fully cover the interface. Our findings indicated that the number of particles per surface area appears to be a crucial parameter in triggering phase inversion, regardless of the particle concentration. The phase inversion mechanism of our solid-stabilized emulsion can be explained by the relationship between the initial particle coverage of the interface and the coalescence rate of the system.