Detergent stabilized oil in water (OW) emulsions are ubiquitous. While in certain applications, long time stability of these emulsions is desired, it can also be a nuisance in other situations. Stable emulsions cause concerns in various Armed Forces bilgewater applications as the extraction of water from the oily wastewater is expensive and becomes technically challenging. Understanding the causes underlying the formation of such emulsions should provide strategies to suppress the formation of such emulsions altogether. Furthermore, when they are formed, water can be extracted from the emulsion inexpensively, and efficiently. While the main objective of this research is to develop the fundamental understanding of OW emulsification, researchers will also develop methods to thwart such emulsifications by taking advantage of the knowledge gained from the same studies.
The approach of this research is guided by the two sciences: surface chemistry and fluctuating hydrodynamics, specifically focusing on two important mechanisms of emulsification identified by the researchers. One type of emulsification results from the penetration of liquid jet through a thin oil film contaminated water in a tank. The other type of emulsification results from a Marangoni force induced instability of the interface. All these lead to hydrodynamic fluctuations having two distinct regimes: one being the turbulent inertial regime driven by hydrodynamic pressure fluctuation and the other is the turbulent viscous regime that leads to the formation of nano-emulsions. While the hydrodynamic pressure fluctuation can be analyzed from the random motion of a small probe on the surface of, or immersed in, water, researchers need to develop a fluorescence based molecular stress measurement method to examine the behavior of small scale turbulent eddies in the viscous turbulent regime.
These studies will be conducted in conjunction with efforts to thwart emulsification using environmentally benign additives that will either inhibit the formation of turbulent eddies and/or discourage the emulsification via a surface chemical route, e.g. scavenging the emulsions by complex coacervation. In order to develop an in-depth understanding of the chemo-hydrodynamic phenomena underlying emulsification, researchers will also carry out extensive measurements of the various interfacial properties of the oil/water interfaces, such as dynamic surface tension, electro kinetics, and the behavior of spreading of films on a Langmuir balance that will also provide information of the elastic as well as the viscous properties of various interfaces.
The researchers expect the research will advance the emulsion science by bridging the gap between the surface chemical and the fluctuating hydrodynamic domains of the existing science. This understanding can be used to develop novel strategies to thwart emulsification. This strategy can be either based on surface chemistry, whereby emulsification will be arrested via complex coacervation, or by suppressing the turbulent eddies. Based on these studies, researchers will be able to make direct recommendations on what needs to be done to thwart the emulsification process, and how to extract oil and surfactant free water inexpensively and efficiently.