Multicomponent PFAS sorption and desorption in common commercial adsorbents: Kinetics, isotherm, adsorbent dose, pH, and index ion and ionic strength effects

Anthony C Umeh; Masud Hassan; Maureen Egbuatu; Zijun Zeng; Md Al Amin; Chamila Samarasinghe; Ravi Naidu

doi:10.1016/j.scitotenv.2023.166568

Multicomponent PFAS sorption and desorption in common commercial adsorbents: Kinetics, isotherm, adsorbent dose, pH, and index ion and ionic strength effects

Sci Total Environ. 2023 Dec 15:904:166568. doi: 10.1016/j.scitotenv.2023.166568. Epub 2023 Aug 24.

Authors

Anthony C Umeh¹, Masud Hassan², Maureen Egbuatu², Zijun Zeng², Md Al Amin², Chamila Samarasinghe¹, Ravi Naidu³

Affiliations

¹ Global Centre for Environmental Remediation (GCER), The University of Newcastle, Callaghan, NSW 2308, Australia; crcCARE, The University of Newcastle, Callaghan, NSW 2308, Australia.
² Global Centre for Environmental Remediation (GCER), The University of Newcastle, Callaghan, NSW 2308, Australia.
³ Global Centre for Environmental Remediation (GCER), The University of Newcastle, Callaghan, NSW 2308, Australia; crcCARE, The University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: ravi.naidu@newcastle.edu.au.

PMID: 37633378
DOI: 10.1016/j.scitotenv.2023.166568

Abstract

The adsorption and desorption of 9 PFAS, including 3 perfluoroalkyl sulphonic and 6 perfluoroalkyl carboxylic acids, in artificial groundwater was investigated using 3 commercial adsorbents that comprised a powdered activated carbon (PAC), a surface-modified organoclay (NMC+_n), and a carbonaceous organic amendment (ROAC). Sorption kinetics and isotherms of PFAS, as well as the effects of adsorbent dose, pH, index ion and ionic strength on PFAS adsorption and desorption were investigated. Sorption of multicomponent PFAS in the adsorbents was rapid, especially for NMC+_n and ROAC, regardless of PFAS chain length. The sorption and (and especially) desorption of PFAS in the adsorbents was impacted by the pH, index ion, and ionic strength of simulated groundwater, especially for the short chain PFAS, with only minimal impacts on NMC+_n and PAC compared to ROAC. Although the potential mineral and charged constituents of the adsorbents contributed to the adsorption of short chain PFAS through electrostatic interactions, these interactions were susceptible to variable groundwater chemistry. Hydrophobic interactions also played a major role in facilitating and increasing PFAS sorption, especially in adsorbents with aliphatic functional groups. The desorption of PFAS from the adsorbents was below 8 % when the aqueous phase was deionised water, with no measurable desorption for NMC+_n. In contrast, the desorption of short chain PFAS in simulated groundwater increased substantially (30-100 %) in the adsorbents, especially in ROAC and NMC+_n, but more so with ROAC. In general, the three adsorbents exhibited strong stability for the long chain PFAS, especially the perfluoroalkyl sulphonic acids, with minimal to no sorption reversibility under different pH and ionic composition of simulated groundwater. This study highlights the importance of understanding not only the sorption of PFAS in groundwater using adsorbents, but also the desorption of PFAS, which may be useful for decision making during the ex-situ and in-situ treatment of PFAS-contaminated groundwater.

Keywords: Adsorbents; Groundwater; Ionic chemistry; Short and long chain PFAS mixtures; Sorption and desorption; pH.