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Research article - Peer-reviewed, 2020

The Adsorption of Per- and Polyfluoroalkyl Substances (PFASs) onto Ferrihydrite Is Governed by Surface Charge

de Campos Pereira, Hugo; Berggren Kleja, Dan; Sjöstedt, Carin; Ahrens, Lutz; Klysubun, Wantana; Gustafsson, Jon Petter

Abstract

An improved quantitative and qualitative understanding of the interaction of per- and polyfluoroalkyl substances (PFASs) and short-range ordered Fe (hydr)oxides is crucial for environmental risk assessment in environments low in natural organic matter. Here, we present data on the pH-dependent sorption behavior of 12 PFASs onto ferrihydrite. The nature of the binding mechanisms was investigated by sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy and by phosphate competition experiments. Sulfur K-edge XANES spectroscopy showed that the sulfur atom of the head group of the sulfonated PFASs retained an oxidation state of +V after adsorption. Furthermore, the XANES spectra did not indicate any involvement of inner-sphere surface complexes in the sorption process. Adsorption was inversely related to pH (p < 0.05) for all PFASs (i.e., C-3-C-5 and C-7-C-9 perfluorocarboxylates, C-4, C-6, and C-8 perfluorosulfonates, perfluorooctane sulfonamide, and 6:2 and 8:2 fluorotelomer sulfonates). This was attributed to the pH-dependent charge of the ferrihydrite surface, as reflected in the decrease of surface zeta-potential with increasing pH. The importance of surface charge for PFAS adsorption was further corroborated by the observation that the adsorption of PFASs decreased upon phosphate adsorption in a way that was consistent with the decrease in ferrihydrite zeta-potential. The results show that ferrihydrite can be an important sorbent for PFASs with six or more perfluorinated carbons in acid environments (pH <= 5), particularly when phosphate and other competitors are present in relatively low concentrations.

Published in

Environmental Science and Technology
2020, volume: 54, number: 24, pages: 15722-15730

Authors' information

Swedish University of Agricultural Sciences, Department of Soil and Environment
Swedish University of Agricultural Sciences, Department of Soil and Environment
Swedish University of Agricultural Sciences, Department of Soil and Environment
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Klysubun, Wantana
Synchotron Light Research Institute (SLRI)
Gustafsson, Jon Petter (Gustafsson, Jon-Petter)
Swedish University of Agricultural Sciences, Department of Soil and Environment
Gustafsson, Jon Petter (Gustafsson, Jon-Petter)
Royal Institute of Technology (KTH)

UKÄ Subject classification

Organic Chemistry
Environmental Sciences related to Agriculture and Land-use
Environmental Sciences

Publication Identifiers

DOI: https://doi.org/10.1021/acs.est.0c01646

URI (permanent link to this page)

https://res.slu.se/id/publ/109994