Estimation of the Acid Dissociation Constant of Perfluoroalkyl Carboxylic Acids through an Experimental Investigation of their Water-to-Air Transport
Abstract
The acid dissociation constants (pKas) of perfluoroalkyl carboxylic acids (PFCAs) have been the subject of discussion in the literature; for example, values from -0.2 to 3.8 have been suggested for perfluorooctanoic acid (PFOA). The dissociated anionic conjugate bases of PFCAs have negligible air-water partition coefficients (KAWs) and do not volatilize from water. The neutral acids, however, have relatively high KAWs and volatilization from water has been demonstrated. The extent of volatilization of PFCAs in the environment will depend on the water pH and their pKa. Knowledge of the pKas of PFCAs is therefore vital for understanding their environmental transport and fate. We investigated the water-to-air transfer of PFCAs in a novel experimental setup. We used ∼1 μg L(-1) of PFCAs in water (above environmental background concentrations but below the concentration at which self-association occurs) at different water pH (pH 0.3 to pH 6.9) and sampled the PFCAs volatilized from water during a 2-day experiment. Our results suggest that the pKas of C4-11 PFCAs are <1.6. For PFOA, we derived a pKa of 0.5 from fitting the experimental measurements with a volatilization model. Perfluoroalkane sulfonic acids were not volatilized, suggesting that their pKas are below the investigated pH range (pKa <0.3).
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The pKa values of PFASs, such as PFOA, range from -0.2 to 3.8, affecting their ionization at different pH levels and influencing their mobility and behavior in soil environments.
“The pKa values of PFASs, such as PFOA, range from -0.2 to 3.8, affecting their ionization at different pH levels and influencing their mobility and behavior in soil environments [86].”
From Industrial Applications, Environmental Fate, Human Exposure, and Health Effects of PFAS (2025) · cites this paper as [86]
PFSAs are fully dissociated anions in environmental media and tend to accumulate in surface waters.
“PFSAs are fully dissociated anions in environmental media [53] and tend to accumulate in surface waters [31]”
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“The pKa values of PFASs, such as PFOA, range from − 0.2 to 3.8, affecting their ionization at different pH levels and influencing their mobility and behavior in soil environments [86].”
Influential
- Authors
- Vierke, L., Berger, U., & Cousins, I. T.
- Affiliations
- Leuphana University of Lüneburg (DE)
- Stockholm University (SE)
- Corresponding author
- Vierke, Lena
- Venue
- Environmental Science & Technology
- Publisher
- American Chemical Society (ACS)
- Published
- 2013-08-16
- Volume
- 47
- Issue
- 19
- Pages
- 11032-11039
- ISSN
- 0013-936X (ISSN-L)
- 1520-5851
- OpenAlex
- W2050410776
- Cited by
- 153
- References
- 5
- Citations by year
- 2026: 19 · 2025: 31 · 2024: 11 · 2023: 12 · 2022: 17 · 2021: 7 · 2020: 10 · 2019: 11 · 2018: 6 · 2017: 9 · 2016: 8 · 2015: 6 · 2014: 4 · 2013: 2
- FWCI
- 5.30
- Type
- journal article
- Language
- en
- Open access
- closed
- Licence
- Locations
- Environmental Science & Technology (publishedVersion)
- PubMed (publishedVersion)
- Multilingual Matters (Channel View Publications) (submittedVersion)
- Topics
- Physical Sciences › Environmental Science › Environmental Chemistry › Per- and polyfluoroalkyl substances research
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmaceutical Science › Fluorine in Organic Chemistry
- Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Toxic Organic Pollutants Impact
- Keywords
- perfluorinated carboxylic acids, acid dissociation constants, perfluorooctanoic acid, air-water partition coefficient, water pH, perfluorinated compounds, environmental fate
- MeSH terms
- Air, Carboxylic Acids, Fluorocarbons, Volatilization, Water, Water Pollutants, Chemical
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