Air-water interfacial adsorption of C4-C10 perfluorocarboxylic acids during transport in unsaturated porous media

Ying Lyu; Baohua Wang; Xinqiang Du; Bo Guo; Mark L Brusseau

doi:10.1016/j.scitotenv.2022.154905

Air-water interfacial adsorption of C4-C10 perfluorocarboxylic acids during transport in unsaturated porous media

Sci Total Environ. 2022 Jul 20:831:154905. doi: 10.1016/j.scitotenv.2022.154905. Epub 2022 Mar 30.

Authors

Ying Lyu¹, Baohua Wang², Xinqiang Du², Bo Guo³, Mark L Brusseau⁴

Affiliations

¹ Key Lab of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130026, PR China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun 130026, PR China; Institute of Water Resources and Environment, Jilin University, Changchun 130026, PR China. Electronic address: yinglyu@jlu.edu.cn.
² Key Lab of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130026, PR China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun 130026, PR China.
³ Department of Hydrology and Atmospheric Sciences, University of Arizona, 429 Shantz Bldg., USA.
⁴ Department of Hydrology and Atmospheric Sciences, University of Arizona, 429 Shantz Bldg., USA; Department of Environmental Science, University of Arizona, 429 Shantz Bldg., USA. Electronic address: brusseau@arizona.edu.

Abstract

The impact of chain length on air-water interfacial adsorption of perfluorocarboxylic acids (PFCAs) during transport in unsaturated quartz sand was investigated. Short-chain (C4-C7: PFBA, PFPeA, PFHxA, PFHpA) and long chain (C8-C10: PFOA, PFNA, PFDA) PFCAs were selected as a representative homologous series. Surface tensions were measured to characterize surface activities of the selected PFCAs. Miscible-displacement column experiments were conducted for each of the PFCAs to characterize the magnitudes of air-water interfacial adsorption under transport conditions. The transport of the long-chain PFCAs exhibited greater retardation than the short-chain PFCAs. Air-water interfacial adsorption (AWIA) was the predominant source of retention (≥63%) for the long-chain PFCAs. Conversely, AWIA contributed less to retention than did solid-phase sorption for the short-chain PFCAs, with the former contributions ranging from 4% to 40%. Direct examination of the breakthrough-curve profiles as well as mathematical-modeling results demonstrated that transport of the two longest-chain PFCAs was influenced by nonlinear AWIA, whereas that of the shorter-chain PFCAs was not. This disparate behavior is consistent with the input concentration used for the transport experiments in comparison to the respective surface activities and critical reference concentrations of the different PFCAs. Quantitative-structure/property-relationship (QSPR) analysis was applied to characterize the influence of molecular size on air-water interfacial adsorption. The logs of the air-water interfacial adsorption coefficients (K_ia) determined from the transport experiments are a monotonic function of molar volume, consistent with prior QSPR analyses of surface-tension measured values. The K_ia values determined from the transport experiments are very similar to those measured from surface-tension data, indicating that the transport experiments produced robust measurements of AWIA.

Keywords: Air-water interfacial adsorption; Chain length; PFAS; PFCAs; Retention; Sorption.

MeSH terms

Adsorption
Culture Media
Fluorocarbons*
Porosity
Surface Tension
Water*

Substances

Culture Media
Fluorocarbons
Water

Grants and funding

P42 ES004940/ES/NIEHS NIH HHS/United States