(321c) Understanding PFAS Selectivity in Anion Exchange Membrane Systems

The widespread production and use of multi-fluorinated carbon-based substances for a variety of purposes has contributed to the contamination of global water supply in recent decades. Per- and polyfluorinated alkyl substances (PFAS) are an anthropogenic class of chemicals imbued with desirable industrial properties that consequentially result in their difficult remediation once exposed to the environment. Common remediation strategies incorporate adsorption and/or ion exchange technologies to separate such contaminants from water, but often suffer from limitations due to low mass transfer efficiencies, among other issues. Membrane systems use many of the same separation methods currently in use today while enhancing operational potential of adsorption or ion exchange functionalities by boosting mass diffusion through convective flow. Furthermore, these improvements are applicable to the regeneration of such membrane systems, which is a costly drawback to conventional water purification techniques. To this end, commercial microfiltration and ultrafiltration membranes were modified using pore functionalization to incorporate an anion exchange moiety within the membrane matrix. This functionalization was performed with multiple amine-containing polymer networks ranging from weak to strong basic residues. Modified membranes maintained water permeance above 40 LMH/bar. Separation of PFAS from aqueous streams was analyzed for both “long-chain” and “short-chain” analytes, perfluorooctanoic acid and perfluorobutyric acid, respectively. Synthesized membranes demonstrated as high as 90% first-pass rejection of perfluorooctanoic acid. Ion exchange affinity of competitive solution-phase ions was also analyzed. This research advances a versatile membrane platform for environmentally relevant applications that seek to help the global availability of safe drinking water. Research funding was provided by the NIEHS-sponsored University of Kentucky Superfund Research Center.