(313a) Synthesis, Transport Properties, and Benefits of Multifunctional Membrane Platforms for the Separation of Contaminants from Aqueous Environments

Challenges related to environmental remediation of water sources require of more efficient and selective separation technologies, supported by proper understanding of the separation mechanisms. Polyfluoroalkyl substances (PFAS) and heavy metals are examples of organic and inorganic compounds that must be removed. Separation processes using traditional technologies have some benefits and challenges when separating these pollutants from the environment. Benefits are created by design, as for example good adsorption affinity, high exclusion rates, high conversion rates, low energetic requirements, among others. Challenges arise from the limitation of the applicability of these benefits to a large range of targeted pollutants, as well as from the competition of the active sites with naturally present competitors, the fouling of organic matter, etc. Ultimately, these challenges can be reflected on a decrease in the processes’ removal efficiency.

This work introduces the synthesis of multifunctional membrane platforms consisting of pore-functionalized microporous support thin-film composites. The main objective is to take advantage of the benefits from each separation mechanism, and their respective functionalities, to help overcome challenges with environmental remediation technologies. These thin-film composites consist of microfiltration membranes (about 100 nm pores) that can be pore functionalized with diverse responsive, strong acid, or strong basic polyacrylamide hydrogels, with a thin film on top that has nanofiltration (NF) characteristics. Characterization of thermo-responsive poly-N-isopropylacrylamide (PNIPAm) nanofiltration membranes using scanning electron microscope and x-ray photoelectron spectroscopy demonstrate the formation of the thin layer on top of the open microporous structure. The porous support from these membranes adsorbs organics (178 mg PFOA adsorbed/m² membrane at an equilibrium concentration of 70 mg/L), and the simultaneous exclusion from the NF layer allows separations of PFOA and the smaller size heptafluorobutyric acid from solutions containing 70 µg/L of these compounds at a high-water flux of 100 L/m²-h at 7 bar. The synthesis and separation properties of strong acidic and strong basic functionalized porous support NF membranes will be also discussed. This Research has been supported by the NIEHS-SRC Program.