(11a) Fundamental Membrane Science Research Addressing the Water-Energy Nexus

B. D. Freeman

McKetta Department of Chemical Engineering, Center for Materials for Water and Energy Systems (M-WET)

The University of Texas at Austin

200 East Dean Keeton Street, Stop C0400

Austin, TX 78712-1589 USA

This presentation provides an overview of research performed in the Center for Materials for Water and Energy Systems (M-WET), a DOE Energy Frontier Research Center. M-WET’s mission is to discover and understand the fundamental science critical to designing new membrane materials, develop tools and knowledge to predict new materials’ interactions with targeted solutes from recalcitrant water sources, provide fit for purpose water, and recover valuable solutes with less energy. Synthetic membranes are widely used for purifying relatively clean water (e.g., seawater and brackish water desalination, filtering lake and river water, etc.) via reverse osmosis (RO), nanofiltration (NF), electrodialysis (ED), ultrafiltration (UF) and microfiltration (MF) due to low energy requirements of membranes relative to alternative technologies (e.g., thermally-based separations). However, today’s membranes were not designed to treat highly impaired water, (e.g., produced water from oil and gas production, flowback water from fracking operations, etc.) due to extensive fouling and poor separation properties. Existing membranes: (1) are poor at discriminating between ions of the same valence (e.g., Na⁺ v. Li⁺), (2) have low selectivity for many neutral contaminants (e.g., boron, arsenic), (3) are always subject to fouling, (4) exhibit a pernicious tradeoff between permeability and selectivity, and (5) are produced in poorly understood, highly non-equilibrium processes that limit deliberate control of their properties. Lack of basic science understanding prevents: (1) rational tailoring of fouling-resistant membrane surfaces, (2) synthesis of dense membranes with desired functionality to selectively and rapidly permeate or react with specific solutes, and (3) precise tuning of pore size and pore size distribution in UF and MF membranes to prepare highly permeable, selective porous membranes. A major limitation in our ability to directly design membranes of the types discussed is a fundamental lack of predictive understanding of material-solute interactions (ranging from molecular to macroscopic scale). This presentation will focus on recent research results from M-WET that address several of these challenges.