(233a) Dispersion of Crude Oil By Blends of Food-Grade Surfactants: Toward Greener Oil Spill Treatments

For decades, dispersants used for marine oil spills have been formulated with a blend of particular surfactants that are known to ensure effective dispersion at sea. After the Deepwater Horizon spill, interest arose about what alternative surfactants might also be suitable to consider for future use. In this presentation I will very briefly summarize a promising avenue that has emerged through collaborative research in the Center for the Molecular Engineering of Dispersant Systems (CMEDS, led by Vijay John at Tulane, but including dozens of collaborators across the country).

Marine oil dispersants containing blends of the nontoxic surfactants lecithin (L) and Tween 80 (T) may be effective alternatives to traditional, currently stockpiled dispersant formulations containing blends of Tween 80, Span 80, and DOSS (dioctyl sodium sulfosuccinate). In our early work, dispersion effectiveness of lecithin-Tween 80 (L-T) blends in an ethanol solvent was measured for South Louisiana crude oil using baffled flask effectiveness testing, as a function of L:T ratio, surfactant:solvent ratio, solvent composition, and wt% dispersant in oil. The most effective L-T dispersants performed comparably to Tween 80-Span 80-DOSS dispersants.

Two other important findings were that: (1) lecithin-rich L-T dispersants were significantly more effective than Tween 80-rich L-T dispersants with lower or comparable interfacial tension, and (2) all L-T dispersants produced much higher interfacial tension than Tween 80/Span 80/DOSS dispersants. This suggests that interfacial phenomena other than simply lowering interfacial tension may also influence L-T dispersants’ effectiveness. In further work, we sought to learn whether the formation of an interfacial gel or other microscopic process at the interface might be responsible. Most recently, this has led to a correlation between the microemulsion phase diagram and the dispersion effectiveness.

Finally, I will highlight some of closely related advances coming from the work of other colleagues affiliated with the CMEDS.