Using Microemulsion Phase Behavior as a Predictive Model for Lecithin-Tween 80 Marine Oil Dispersant Effectiveness

Area of Science:

• Environmental Chemistry
• Surfactant Science
• Colloid and Surface Chemistry

Background:

• Traditional marine oil dispersants raise environmental concerns regarding persistence and toxicity.
• Development of "greener" dispersants using food-grade surfactants like lecithin (L) and Tween 80 (T) is ongoing.
• Lecithin and Tween 80 individually show poor oil dispersion, but their mixtures (LT blends) exhibit synergistic effectiveness, the mechanism of which is unclear.

Purpose of the Study:

• To investigate the correlation between the thermodynamic phase behavior of lecithin-Tween 80 (LT) blends and their effectiveness as marine oil dispersants.
• To establish a predictive model for designing effective and environmentally friendly oil dispersants.

Main Methods:

• Studied ternary systems of LT dispersant (D), hexadecane (model oil, O), and synthetic seawater (W) across various L:T weight ratios (0:100 to 100:0).
• Determined phase diagrams, specifically identifying Winsor III microemulsion regions (coexistence of microemulsion with oil and water phases).
• Utilized hydrophilic-lipophilic deviation (HLD) calculations and developed a rapid protocol (hours) for observing phase behavior.

Main Results:

• The most effective LT dispersants (60:40 and 80:20 L:T ratios) induced broad Winsor III microemulsion regions in the DOW phase diagrams.
• Observed correlations between phase behavior and dispersant effectiveness were generally consistent with HLD predictions, though some exceptions were noted.
• A fast protocol for phase behavior observation was established, facilitating quicker assessment of dispersant potential.

Conclusions:

• The thermodynamic phase behavior, particularly the formation of Winsor III microemulsions, is a key indicator of synergistic effectiveness in LT oil dispersants.
• The combination of HLD calculations and the rapid phase behavior protocol offers a predictive tool for formulating efficient marine oil dispersants.
• This approach aids in the rational design of greener, more effective dispersants for oil spill response.