Per- and polyfluoroalkyl substances (PFAS) are highly stable fluorinated compounds, which have been widely used in industrial applications and consumer products. Their structural characteristics include strong carbon−fluorine bonds with a polar functional group (typically a carboxyl or sulfonate) and a nonpolar fluorinated carbon chain. As a result of their widespread use, resistance to degradation, and ability to bioaccumulate, PFAS have been detected in both wildlife and humans.The presence of PFAS in human serum has been well-documented. Potential routes of human exposure include air inhalation, dust ingestion, dermal absorption, and dietary intake. Volatile PFAS degrade to ionizable perfluoroalkyl acids (PFAAs) where little is known about their transport in air as few materials exhibit the properties to trap them. Better materials are needed to measure their current concentration, their effect on the environment, and methods to sequester them. Here, we report the study of the gravimetric dynamic sorption of short-chain PFAAs (C = 4-7) on a series of sorbent materials. Three PFAAs were studied: perfluoro-butane-sulfonic acid (PFBS), perfluoro-butanoic acid (PFBA), perfluoro-pentanoic acid (PFPeA). Despite the vapor pressure of these PFAAs (ca. 0.01 – 10 mmHg) a remarkable sorbent weight increase was observed upon exposure. Polymer-based material exhibited sharp uptake kinetics for PFPeA and PFBS, albeit low capacity (ca. 1 wt. %) and a linear uptake of PFBA was observed (ca. 2 wt. %/hr). Metal-organic frameworks (MOFs) exhibited a linear uptake of PFBS (ca. 15 wt. %/hr), and an equilibrium uptake of PFPeA and PFBA of ca. 1.5 wt. % each. Furthermore, we developed a polymer-MOF composite (RTI’s kollaMOF technology) for the capture of PFAS from water. The polymer-MOF composite captured ca. 2000 ppm PFBA from a 5000 ppm concentration in DI H2O in less than 2 hours.

Adsorbing Per- and Polyfluoroalkyl substances in air and water

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ACS Fall 2022

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