The global demand for energy continues to increase at a rapid pace, and projections indicate that oil will remain a major fuel source for many decades. The accidental release of oil in bodies of water due to negligence or mishap represents a significant environmental threat because of oil’s insolubility in water. If left untreated, a film of oil remains concentrated at the air-water interface, resulting in significant damage to sensitive marine ecosystems. An obvious solution to minimizing the environmental damage is the use of dispersants to break up the spill. For this reason, over 7 million liters of dispersants (such as Corexit EC9500A) were applied to mitigate the environmental impact after the Deepwater Horizon disaster in 2010.
Dispersants are composed of small amphiphilic molecules bearing both a hydrophilic face and a hydrophobic face that stabilize oil microdroplets in an emulsion by acting as a compatibilizing interface between the two incompatible phases. Although such compounds have been successfully developed and applied to stabilizing emulsions in closed systems (e.g. bottles of salad dressing), they suffer from a critical weakness: oil remediation by surfactants such as Corexit occurs through non-equilibrium emulsification of oil droplets into unstable structures that require constant energy input, from unreliable natural sources such as wind, waves, and currents, to prevent re-coalescence of the oil (analogous to having to shake the bottle of salad dressing before use, but on the size scale of an ocean.) The surfactant merely slows down the coalescence; it does not prevent it. As such, the dispersant needs to be continually re-applied over time, at great financial expense. In addition, emulsified oil droplets become more bioavailable within the marine environment. Ideally the dispersed oil would exhibit minimal toxicity to aquatic life but be colloidally stable such that it can be bioremediated over a time scale longer than that of re-coalescence.
The objective of the proposed research is to develop a platform of next-generation oil dispersants with superior uptake and stability, but with reduced toxicity, compared to existing remediation technologies. Our general approach involves the study of unimolecular micelles (UMs), which are materials that can stably encapsulate oil under any concentration conditions without requiring energy input. UMs have the remarkable property of dispersing oil in an equilibrium state, regardless of the environment. Based on our previous studies, UMs can be produced using a nanoparticle template, and we hypothesize that this platform can be extended to additional templates to elucidate how structural factors in the dispersant design affect performance (payload capacity, stability, toxicity) and cost. Our comprehensive approach will involve the synthesis and physiochemical characterization of novel dispersants, while integrating studies that determine nanotoxicological effects in fish development and growth. The proposed research team is composed of experts in nanoparticle and polymer synthesis (Grayson, Savin), solution process characterization (Reed, Savin), and aquatic nanotoxicology (Denslow). From a fundamental standpoint, successful completion of the proposed research will establish a matrix of dispersant design parameters and corresponding structure/property/toxicity relationships. From a commercial standpoint, the proposed research will result in cost-effective materials that can be applied to a broad range of environments (e.g. salt or fresh water across a wide range of temperature).