Abstract

Current water purification membrane technologies cannot readily treat the high concentration and multi-component produced water (PW) from oil and gas operations. This stems, in part, from membrane fouling induced by a diverse array of organic and inorganic PW constituents. At present, the design of antifouling membrane materials relies on macroscale heuristics such as ensuring the smoothness, charge neutrality, and hydrophilicity of the membrane surface. For instance, hydrophilic coatings such as polyethylene oxide (PEO)-based hydrogels dramatically increase resistance to organic components of feedwater. This antifouling property is hypothesized to originate from the formation of a bound water layer at the membrane surface that resists adsorption of hydrophobic molecules; however, the molecular-scale drivers of membrane fouling remain underexplored.

This work leverages detailed atomistic molecular simulations to elucidate the molecular-scale determinants of water properties at aqueous interfaces. First, water’s collective molecular structure is shown to strongly relate to equilibrium water dynamics in PEO-water mixtures. Then, high-throughput molecular dynamics simulations and a statistical learning workflow reveal persistent connections between water structure and functional thermophysical properties in aqueous environments. Finally, free energetic calculations detail foulant interactions with a model antifouling PEO brush surface. Further analysis demonstrates that solute-brush affinities are driven by the entropy of solution restructuring induced by foulant sorption.