Determining the Surface p<i>K</i><sub>a</sub> of Perfluorooctanoic Acid
Lila J. Musegades, Owen P. Curtin, Jenée D. Cyran
Abstract
High Resolution Image Download MS PowerPoint Slide 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 p K 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 p K 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.