Date of Award

2019

Degree Type

Thesis

Degree Name

Master of Science in Chemical Engineering (MSChE)

Specialization

Environmental Engineering

Department

Chemical Engineering

First Advisor

Geoffrey Bothun

Abstract

The Deepwater Horizon disaster in 2010 led to the release of 200 million gallons of crude oil into the ocean, and really put into perspective the amount of damage that man can inflict on the environment. One way that first responders attempted to deal with the spill was by dispersing the oil into the water column with the use of a chemical mixture known as Corexit 9500. Being sprayed onto the slick from above, and down near the wellhead below, this mixture of surfactants and solvents was aimed at stopping the slick from reaching the coast and also speeding up the bioremediation process by increasing the specific surface area of the slick. And while Corexit has been shown in prior studies to be effective at performing this task, certain components that make up Corexit, mainly the surfactant dioctyl sodium sulfosuccinate (DOSS), have environmental concerns surrounding them including effects to human health, persistence in the ocean and possible impairment of the bacterial oil degradation. Therefore, there is a need for a more environmentally friendly dispersant.

Recently, an alternative dispersant mixture being composed of the food grade amphiphiles lecithin and Tween 80 has shown much promise in exhibiting similar dispersant effectiveness as Corexit 9500. The studies performed in this thesis investigate these mixtures further, while also trying to understand the dispersion and degradation processes.

The first manuscript investigates a solvent free mixture of lecithin and Tween 80, being composed of lecithin and Tween 80 assemblies formed in water. Investigation through Cryo TEM revealed that the combination of these two amphiphiles forms bicelles in water. Dispersant effectiveness testing showed the lecithin/Tween 80 solvent free system to be effective at forming a stable emulsion.

The second manuscript investigates the oil biodegradation process of oil with Alcanivorax borkumensis when supplemented with a variety of dispersant mixtures. Emphasis was given to the newly developed lecithin-Tween 80 mixture, which was compared to the controls of no dispersant and Corexit 9500. Lecithin alone and Tween 80 alone dispersant mixtures were also tested in order to elucidate whether it is the rise in bioavailability or the presence of one of the two surfactants that gives the lecithin-Tween 80 mixture its degradation behavior. Microscopic analysis of the systems showed the presence of bacteria-oil agglomerates for all but Tween 80. And oil degradation quantification results after 144 hours showed lecithin/Tween 80 to enhance degradation the most, at 52%; compared to no dispersant at 25%, Corexit 9500 at 35%, Tween 80 at 35% and lecithin at 38%.

Available for download on Monday, April 19, 2021

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