Dispersing Crude Oils of Varying Viscosities Using a Food-Grade Dispersant

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Aljirafi, Futoon Osama
Raghavan, Srinivasa R
The mitigation of crude oil spills in the ocean is generally done using chemical dispersants, which convert the oil slick into small droplets. These dispersants are mixtures of surface-active molecules (surfactants) dissolved in a solvent. Questions regarding the toxicity of current commercial dispersants have prompted our lab to develop an eco-friendly alternative based on the food-grade surfactants, soy lecithin (L) and Tween 80 (T). In previous studies, the roles played by L/T and the solvent in a typical dispersant have been studied, but all those studies were done with a light crude oil, i.e., one with a low viscosity. In this thesis, we examine if our food-grade dispersant remains effective at dispersing heavier crude oils, i.e., crudes of higher viscosity. We study a light, a medium, and a heavy crude and compare their dispersion into seawater using a fixed L/T blend in various solvents. As expected, we find that the efficiency of dispersion is lower when the crude is more viscous. Moreover, in line with our previous findings, simply varying the solvent can alter the dispersion efficiency from poor to good. The solvents that promote dispersion can be identified systematically by using a plot of Hansen Solubility Parameters (HSPs). However, there do exist several key differences between the solvents most effective for the three crudes. Our analysis suggests that crude oil composition must be taken into account when optimizing the formulation of a dispersant.