RII Track-4: Use of Positron Annihilation Lifetime Spectroscopy to Engineer Membrane Selective Layers

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This project seeks to build on the water research at The University of Alabama at Tuscaloosa (UA). With a wealth of natural water sources and access to the Gulf of Mexico, Alabama is an ideal location for research in water treatment processes. As such, UA has made water one of its four research pillars to provide better water quality for all people. Polyamide membranes, often called reverse osmosis or RO membranes, are commonly used for seawater desalination. However, their molecular level properties are not well understood. This project will allow researchers from UA to conduct studies at the National Institute of Standards and Technology (NIST) to learn a new technique to characterize the molecular-level properties of water treatment polymer membranes. This research seeks to understand how synthesis conditions affect membrane performance at the molecular level, specifically those involved in seawater desalination. The polymer characterization technique will be of great benefit to make these membranes more energy-efficient and cost-effective. This work will initially provide training for one graduate student, and results will be integrated into undergraduate curriculum and research. The research collaboration formed through this project will help develop capacity at UA to characterize polymers using cutting-edge technology, providing additional opportunities to educate and train graduate and undergraduate students.The goal of the proposed project is to engineer polyamide membrane separation layers by utilizing Positron Annihilation Lifetime Spectroscopy (PALS). PALS is used to probe material defects, voids, and free volume at the sub-nm scale and is therefore useful for characterizing porous materials, such as polymeric membranes. Polyamide membrane separation layers will be synthesized via the reaction between the monomers m-phenylenediamine and trimesoyl chloride. Polymerization conditions such as monomer concentration and polymerization time will be varied to determine how each affects the polyamide separation layer free volume on a molecular level instead of a macroscopic level. Free volume characterization of the polyamide membrane separation layers will be performed using the PALS system at NIST. The use of a PALS system will allow for the development of a more basic understanding of how these polyamide membranes separate on a molecular level and what factors influence the free volume and separation properties of these polymeric membranes. By understanding the fundamental reason why polymerization conditions affect polyamide free volume, and therefore the desalination performance on the molecular level, polyamide membranes can be engineered to make membrane-based separation processes more energy-efficient and cost-effective. The collaboration developed between UA and NIST will generate high-quality undergraduate and graduate research opportunities in the field of water treatment while advancing one of UA's research pillars to raise the bar in the quest for better water for all.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.