Emulsion Separation Using the Motion of a Confined Droplet

Abstract

Separations of emulsions are important to many consumer products and industrial processes. A new way of emulsion separation is proposed here using long droplets in capillary tubes. A suspension of colloidal particles of micron diameter can be separated by the thin film interface between a droplet and the glass of a small capillary tube as the droplet moves forward through the fluid. This idea has been mathematically defined by previous work in “Armoring confined bubbles in the flow of colloidal suspensions” by Yu, et al. (2017, 2018) and by the characterization of the flow in “The motion of long bubbles in tubes” (Bretherton, 1961). Using these two ideas as a framework, a new experiment was designed in order to test two new variables. The first is whether separation can occur through a liquid-liquid interface of heavy mineral oil and water. The second is whether emulsions, rather than colloidal particle suspensions, can be separated using this method. The properties of this new system, such as droplet length, shape, speed, and viscosity are discussed, and followed by a test of emulsion separation between heavy mineral oil and water. Results show that defined film thickness (b) values can be accomplished and controlled through different speeds and droplet lengths, but emulsion separation requires specific controls in order to be successful. While this new method is fast and inexpensive compared to alternative emulsion separation methods, the difficulty in creating successful trial runs is a determent to its viability as a future commercial method. Further research ideas may be able to mitigate some of these issues and are discussed in the conclusion.