Molecular Simulation of the Partitioning Phenomena of Oil and Dispersant Components in Air-Seawater-Oil System

As majority of research on chemical dispersants, their interactions with oil, and the effects that dispersant-oil mixtures has been focused primarily on toxicology, yet studies on molecular scale phenomena are important to obtain a fundamental understanding of how the components of chemical dispersants and oil interact at different interfaces, such as the air-seawater and the oil-seawater. Here we report simulation results of the partitioning of several Corexit components [i.e. sodium dioctyl sulfosuccinate (DOSS), Span 80, as well as solvents such as dipropyl glycol butyl ether (DPGE)] between model seawater and oil phases especially heavy oil. These results are relevant to biodegradation and toxicological studies. Experimental researchers simulate the mixing of fresh oil, seawater, and dispersant using a prescribed lab protocol; the resulting aqueous phase (termed chemically-enhanced water accommodated fraction, or CEWAF) is then separated from the oil phase and used for biodegradation or toxicology exposure studies in the lab. However, preliminary results suggest that CEWAFs prepared using the prescribed lab protocol are representative of only a small subset of environmental conditions, which do not include oil spills in the Arctic (e.g., Exxon Valdez), oil weathering effects, or the direct injection of Corexit in the turbulence of the Macondo wellhead in the Gulf of Mexico. Therefore, as part of our initial efforts in this topic, molecular dynamics (MD) simulation is performed to study the partitioning of Corexit components between model seawater and oil phases. Results and discussion will be presented.