Emulsion Stabilization by Amphiphiles and Particles
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During a marine oil spill, oil spreads with the ocean currents and contaminates wildlife and the environment. One of the most economically viable schemes for oil removal is the employment of dispersants. Dispersant use allows for rapid treatment of large areas and helps accelerate the natural biodegradation process by increasing the surface area of oil available to bacteria. Even though current dispersants are relatively non-toxic, they still add solvents and contaminants to the environment due to the fact that large volumes of these are used. The objective of this thesis is to explore the use of mineral particles and other naturally occurring substances in dispersants in order to reduce the amount of surfactants and/or solvents utilized and to develop formulations that have low impact on the environment. We have employed silica particles and surfactants and we have investigated their effectiveness in stabilizing water-in-oil emulsions. Emulsion stability was evaluated using components of oil as representative samples. Specifically, toluene was used as an aromatic hydrocarbon component and n-hexadecane as an aliphatic hydrocarbon. A non-ionic block copolymer, Pluronic F127 ® , PEO100-PPO70-PEO100 and an anionic surfactant, Sodium bis(2-ethylhexyl) sulfosuccinate (AOT), were separately employed as surfactant additives for emulsion stabilization. Silica particles, LUDOX TM50TM, having an average diameter of 26 nm and surface area of about 140 m 2 /g, were used together with the surfactants to mimic naturally occurring particles. Emulsion stability of samples containing oil and water where surfactants and/or particles were added was evaluated by means of phase behavior. Emulsified samples were visually inspected to determine the volume fractions of emulsion, aqueous, and oil phases and their changes over time. Optical microscopy images of emulsion droplets were used for the droplet size distribution characterization of the obtained emulsions. It was found that silica particles alone were unable to stabilize toluene-water or n-hexadecane-water emulsions, whereas both Pluronic F127 and AOT can better stabilize these emulsions when used alone. We were however, able to successfully achieve an increase in emulsion stability by adding silica particles to samples with low surfactant concentrations (where the surfactant alone does not provide stable emulsions), thus demonstrating that particles and surfactants can act synergistically to stabilize emulsions.