Ethyl Cellulose Nanoparticles and Porous Media: Fundamentals and Applications

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The discharge of non-aqueous phase liquids in the course of transportation or industrial activity is a cause of grave concern for the health of both surface and subsurface aquatic environments. Their removal from the subsurface in particular, is a vexing problem, due to great difficulty with the characterization and targeting of source zones, the monitoring of remediation performance, and the in situ delivery of remediation agents with selectivity toward contaminants. Engineered nanomaterials have great potential to improve the efficacy of existing and novel remediation technologies; however, challenges with material sustainability and barriers to nanoparticle transport and distribution in porous media, have hampered progress towards widespread deployment. The long term vision of this research program is to address these challenges, strategically focusing our immediate efforts over the next five years on an emerging sustainable nanomaterial, ethyl cellulose (EC), derived from abundantly available cellulose. Capitalizing on our quantitative understanding of the role surface forces play in the attachment and assembly of EC nanoparticles (NPs) at gas--liquid and liquid--liquid interfaces, we will use EC- NP suspensions as a model system to investigate NP interactions with mobile and immobile fluid--fluid interfaces  in porous media (i.e., at the pore- network and continuum scales). The systematic characterization of physical processes operative at different scales is a distinguishing feature of the proposed research program. Fundamental knowledge gained from the study of EC-NPs will enable the rational development of applications based not only on EC-NPs, but on more complex sustainable nanomaterials derived from cellulose or lignin. The proposed research program will unfold in two main directions. The first will investigate, using experiments and simulations, fundamental aspects of EC-NP transport in host porous media (soil and rock), under conditions of single-, two- and three--phase flow. This is important because NP attachment at fluid interfaces affects and is affected by the dynamics of immiscible displacement - dynamics which underpin applications in subsurface remediation (e.g., NP--stabilized foam flooding, contaminant sensing by NPs, immobilization of hydrophobic contaminants, in situ contaminant barriers), oil recovery and monument preservation. The second direction will address experimentally the use of oil--water (O/W) emulsions stabilized by EC- NPs as templates for the creation of hydrophobic/oleophilic porous materials used for O/W separation and as coatings for wettability control. Ultimately, this research will lead to the development of sustainable technologies and the training of highly-qualified personnel at the interface of colloid science and transport in porous media, fields seeing significant growth and requiring highly trained personnel as advanced materials are beginning to be deployed in geologic settings.