Date of Award

Fall 11-16-2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Yun Chen

Abstract

Emulsions are suspensions of droplets dispersed into an immiscible liquid phase, with at least a water phase and an oil phase. The capability to incorporate both hydrophilic and hydrophobic components makes emulsions amenable to a variety of applications, such as bilgewater treatment and oil recovery. To optimize bilgewater treatment or oil recovery, many aspects must be considered, such as the effect of emulsion stability, the wetting conditions and, more in general, the possibility to characterize droplet’s behavior over static or dynamic conditions. This thesis investigates the roles of surfactants and nanoparticles in understanding droplet behavior in oil-water systems, with a specific focus on bilge water treatment and enhanced oil recovery (EOR). The study aims to improve the efficiency of oil-water separation, a critical process for environmental protection in maritime settings and for maximizing oil extraction from underground reservoirs. The study begins with an analysis of the dynamic interfacial tension (IFT) behavior of two surfactants, Triton X-100 and Glucopon 225 DK, measured using the pendant drop method. The critical micelle concentrations (CMC) of these surfactants were determined, revealing that Triton X-100 has a significantly lower IFT compared to Glucopon 225 DK. In the next step, from the interfacial tension obtained during the experimental work, key adsorption parameters, including the maximum surface concentration (Γ∞) and the equilibrium constant (κ), were derived using the Langmuir adsorption isotherm. These parameters provide clear insight of surfactants characteristics and their role in separate of oil from water to provide cleanliness component. The second part of this study focuses on the dynamic role of silica nanoparticles in improving the wettability of surface to increase the extraction of oil from underground reservoirs to see their potential in altering reservoir rock wettability from strongly oil wet to water wet. Additionally, by using simulation the effect of various surface wettability on the droplet behavior was investigated by using COMSOL simulation. The results indicate that Glucopon 225 DK exhibits a higher surface coverage (Γ∞), meaning more surfactant molecules cover the droplet interface, while Triton X-100 shows a higher affinity (κ) for the oil-water interface and greater diffusivity. From studying nanoparticle impact on improving surface wettability, it was observed that even small amount of SiO2 nanoparticle can increase the hydrophilicity of the surface and make the surface more favorable for oil recovery industry. From the COMSOL simulation, it was observed that how wettability of surface can change the droplet behavior. At complete oil wet surface, the oil droplet can get stuck to the surface or undergo breakup or deformation. However, by altering the surface to more hydrophilic, the oil droplet can move smoothly which is favorable to extraction of oil. The significance of this study lies in its potential to prevent environmental pollution and oil extraction from existing wells before moving on to newly discovered fields. Despite the fact that the previous experimental work has focused on microscale droplets with insoluble surfactants, most of those studies focused on the systems that follow the Bancroft rule, where the surfactants are soluble in the continuous phase. Few of the seminal studies have performed experiments using soluble surfactants or surfactants inside droplets, which can be more relevant to some key applications, such as the treatment of bilgewater. However, in this study, the effect of surfactant in the dispersed phase is investigated. Also, in considering improving the surface wettability, the impact of high concentration of nanoparticle were observed statically. In this study, however, the temporal efficiency of dilute nanoparticles of SiO2 was investigated to see their potential in improving oil droplet movement in oil-water systems.

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