A group-contribution model for predicting the physicochemical behavior of PFAS components for understanding environmental fate

Song-Thao Le; Tohren C G Kibbey; Kela P Weber; William C Glamore; Denis M O'Carroll

doi:10.1016/j.scitotenv.2020.142882

A group-contribution model for predicting the physicochemical behavior of PFAS components for understanding environmental fate

Sci Total Environ. 2021 Apr 10:764:142882. doi: 10.1016/j.scitotenv.2020.142882. Epub 2020 Oct 14.

Authors

Song-Thao Le¹, Tohren C G Kibbey², Kela P Weber³, William C Glamore¹, Denis M O'Carroll⁴

Affiliations

¹ School of Civil and Environmental Engineering, Water Research Centre, University of New South Wales, Sydney, NSW 2052, Australia.
² School of Civil Engineering and Environmental Science, University of Oklahoma, Norman, OK 73019, USA.
³ Environmental Sciences Group, Royal Military College of Canada, Kingston, ON, Canada.
⁴ School of Civil and Environmental Engineering, Water Research Centre, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: d.ocarroll@unsw.edu.au.

PMID: 33127153
DOI: 10.1016/j.scitotenv.2020.142882

Abstract

The factors controlling per- and polyfluoroalkyl substances (PFAS) environmental fate remains the subject of considerable debate and study. As surfactants, PFAS readily partition to interfaces, a property that controls their transport and fate. A group contribution model is developed to predict the extent to which PFAS partitions to the air-water interface. Langmuir adsorption and Szyszkowski equation parameters were fitted to literature air-water surface tension data for a range of PFAS and conventional hydrocarbon surfactants. This approach enabled the prediction of the impact of the hydrophilic head group, and other molecular components, on PFAS interfacial partitioning in instances when PFAS data are unavailable but analogous hydrocarbon surfactant data are available. The model was extended to predict a range of parameters (i.e., solubility, critical micelle concentration (CMC), K_D, K_oc and K_ow) that are used to predict PFAS environmental fate, including long-range PFAS transport and in multimedia models. Model predictions were consistent with laboratory and field derived parameters reported in the literature. Additionally, the proposed model can predict the impact of pH and speciation on the extent of PFAS interfacial partitioning, a potentially important feature for understanding the behaviors of some ionizable PFAS, such as fluorinated carboxylic acids. The proposed model provides a conceptually straightforward method to predict a wide range of environmental fate parameters for a wide range of PFAS. As such, the model is a powerful tool that can be used to determine parameters needed to predict PFAS environmental fate.

Keywords: Air-water interface; Interfacial partition coefficient; Multimedia model; PFAS; Standard free energy of adsorption; Surface tension; Surfactants.