UC Santa Barbara

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 a diverse array of organic and inorganic solutes. 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 natural organic matter. This anti-fouling 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 basis for this antifouling property is not well understood. This work leverages detailed atomistic molecular simulations to elucidate the molecular scale determinants of water properties at aqueous interfaces. First, we implement a synergistic computational-experimental approach to unveil the persistent connection between water’s collective molecular structure and equilibrium water dynamics in aqueous solutions. Then, high-throughput molecular dynamics simulations and a statistical learning workflow reveal persistent connections between water structure and functional thermophysical properties in aqueous environments. Further, unsupervised learning (principal component analysis) reveals hidden signatures of water structuring on small (<1 nm) and large length scales. Finally, free energetic calculations detail foulant interactions with a model antifouling PEO brush surface. Further analysis demonstrates that foulant-surface interactions are driven by a combination of direct interaction (energetic) and solution restructuring (entropic) contributions.