Optimization of Polymer-Surfactant Systems for the Remediation of Deep Sea Oil Spills

Abstract

The Deepwater Horizon platform explosion and subsequent oil spill in 2010 presented new challenges in oil spill remediation. The deep sea nature and behavior of oil droplets at different time scales informed the need for increased research and development into novel dispersants, such as polymer-surfactant solutions. We will evaluate the synergistic effects of polymers and surfactants on dispersant transport to the oil-water interface, focusing on the dynamics of hydrophobically modified poly(acrylic acid) (hmPAA) and sodium dodecyl sulfate (SDS) and using the air-water interface as a comparison to oil-water. This thesis focuses on the verification of a new method for determining critical aggregation concentration (CAC) through measurement of dynamic surface tension. The CAC is the surfactant concentration at which polymer- surfactant micellization begins and is important because once polymer and surfactants begin forming aggregates, the rate at which surfactants molecules move from the bulk phase to the interface changes. Peaks in dynamic surface tension were observed at surfactant concentrations corresponding to the CAC, indicating the possibility of determining CAC using instantaneous surface tension measurements instead of long equilibrium experiments. Dynamic surface tension measurements were carried out on a range of polymer-surfactant solutions, including hmPAA-SDS, PAA-SDS and PEG-SDS, using a pendant drop tensiometer. The effect of hydrophobic chain length and polymer concentration on surface tension and transport in the solution were also considered. Longer hydrophobic chains result in CACs at lower SDS concentrations while higher polymer concentrations achieve lower surface tensions at lower SDS concentrations. Time lapse experiments were also carried out to inform the behavior of the polymer-surfactant solutions during long time scales.