Determining the Surface pK_a of Perfluorooctanoic Acid

Authors

Lila J. Musegades, Baylor University
Owen P. Curtin, Boise State University
Jenée D. Cyran, Boise State UniversityFollow

Document Type

Article

Publication Date

2-8-2024

Abstract

Perfluorooctanoic acid (PFOA) is an environmentally prevalent and persistent organic pollutant with toxic and bioaccumulative properties. Despite the known importance of perfluorinated pollutants in the global environment, molecular-level details of the physicochemical behavior of PFOA on aqueous interfaces remain poorly understood. Here, we utilized two surface-specific techniques, vibrational sum frequency generation spectroscopy (SFG) and surface tensiometry, to investigate the pH-induced structural changes of PFOA and octanoic acid (OA) and determined the apparent pK_a at the air–water surface. The SFG spectra and surface activity model were investigated over a wide range of pHs. With the surface tension measurements, the surface pK_a values for OA and PFOA are determined to be 3.8 ± 0.1 and 2.2 ± 0.2, respectively. These results could provide insights into improved remediation of PFOAs and may impact climate modeling of perfluorinated alkyl chain molecules.

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.

Publication Information

Musegades, Lila J.; Curtin, Owen P.; and Cyran, Jenée D.. (2024). "Determining the Surface pK_a of Perfluorooctanoic Acid". The Journal of Physical Chemistry C, 128(5), 1946-1951. https://doi.org/10.1021/acs.jpcc.3c07235