CAREER: SusChEM: Engineering Molecular Interactions to Control Ion Transport in Hydrated Polymers for Membrane Separations

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Within the next decade, the removal of salt from salty and contaminated water may be needed to alleviate water shortages in the USA. Also, removal of nitrogen and phosphorus from agricultural runoff may be implemented to prevent eutrophication and remediate a "dead zone" in the Gulf of Mexico. Additionally, novel routes may be developed to recover rare metals that are in short supply in the USA, and subject to export controls, yet are required components of magnets and sensors for military applications and electronics. These three technological challenges--desalination, nutrient recovery, and rare metal recovery--all involve the removal of charged molecules (ions) from water. To separate these ions from water requires selective materials, such as membranes, that allow one type of molecule to pass, while prohibiting others. Minimization of the energy required for the separation increases economic viability. Although current membranes separate molecules based on size and/or charge, they do not currently discriminate between similarly charged ions. This CAREER project will design and synthesize new molecularly-tailored polymer membranes that create unique electrochemical environments to selectively discriminate ions of similar charge, size, and other properties. This project will elucidate the influence of ion properties, molecular confinement, and the polarity of charged groups on ion transport in charged polymer membranes. Fundamental structure-property relationships will be developed for single electrolytes, and extended to ion mixtures. These relationships will be used to tailor the electrochemical environment in the confined nano-space of charged membranes, thereby laying the foundation for rational design of advanced polymeric materials. The chemical structures and morphologies of the new membranes will enable high ion selectivity, and minimize energy consumption of ion separation processes. The mechanical and chemical stability of the membranes will be addressed. An integrated educational plan incorporates the research outcomes into all levels of engineering education, by providing internships for high school students, workshops for high school teachers, dissemination of a web-based membrane performance calculator, incorporation of this calculator into undergraduate courses, direct laboratory training of undergraduate and graduate students, and broad dissemination of research results. The integrated research and education plan will lead to robust membranes to address global water and energy resources that lie at the heart of food-energy-water nexus challenges.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.