Measurement of Aqueous Diffusivities for Perfluoroalkyl Acids

Schaefer, Charles E.; Drennan, Dina M.; Tran, Danielle; García, Raymmah Aleyda; Christie, Emerson; Higgins, Christopher P.; Field, Jennifer A.

doi:10.1061/(asce)ee.1943-7870.0001585

Cited by 37 publications

(38 citation statements)

References 23 publications

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“…Here we take

L

as the length of the computational domain. The aqueous diffusion coefficient

D_{0}

is obtained from measured values reported in Schaefer et al (). The above parameters employed for the simulations in the present work are summarized in Table .…”

Section: Data and Parametersmentioning

confidence: 99%

A Mathematical Model for the Release, Transport, and Retention of Per‐ and Polyfluoroalkyl Substances (PFAS) in the Vadose Zone

Guo

Zeng

Brusseau

2020

Water Resources Research

124

119

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Per‐ and polyfluoroalkyl substances (PFAS) are emerging contaminants of critical concern. As surfactants, PFAS tend to accumulate at air‐water interfaces and may stay in the vadose zone for long times before contaminating groundwater. Yet not well understood, the extent of retention in the vadose zone has critical implications for risk management and remediation strategies. We present the first mathematical model that accounts for surfactant‐induced flow and solid‐phase and air‐water interfacial adsorption. We apply the model to simulate PFOS (a PFAS compound of primary concern) transport in the vadose zone at a model fire‐training area site impacted by aqueous film‐forming foam (AFFF). Air‐water interfacial adsorption is shown to have a significant impact—amplified by the low water content due to gravity drainage—total retardation factors range from 233 to 1,355 for the sand and 146 to 792 for the soil used in the study. The simulations illustrate it can take several decades or longer for PFOS to reach groundwater. Counterintuitively, the lower water content in the sand—due to stronger drainage and weaker capillary retention—leads to retardation factors greater than for the soil. Also, most PFOS is adsorbed at air‐water interfaces with only 1–2% in the aqueous phase. The implications include (1) fine‐texture materials could have lower retardation factors than sand due to higher retained water content, (2) soil PFAS concentrations are likely to be orders of magnitude higher than those in groundwater at source zones. Both implications are consistent with recent field observations at hundreds of AFFF‐impacted sites.

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“…Here we take

L

as the length of the computational domain. The aqueous diffusion coefficient

D_{0}

is obtained from measured values reported in Schaefer et al (). The above parameters employed for the simulations in the present work are summarized in Table .…”

Section: Data and Parametersmentioning

confidence: 99%

A Mathematical Model for the Release, Transport, and Retention of Per‐ and Polyfluoroalkyl Substances (PFAS) in the Vadose Zone

Guo

Zeng

Brusseau

2020

Water Resources Research

124

119

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“…These include media bulk densities (ρ b ), solute dispersivities (α o ), solute diffusivities (D o ), linear sorption coefficients (K d ), K L,aw values, and Γ max values for each PFAS solute. Diffusivities were derived from the recent work of Schaefer et al [51]. K d values were the interpolated values provided by Guelfo and Higgins [15].…”

Section: Example Simulation-1d Transport Transient Flow Condition Homogeneous Profilementioning

confidence: 99%

A Modified HYDRUS Model for Simulating PFAS Transport in the Vadose Zone

Silva

Šimůnek

McCray

2020

Water

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The HYDRUS unsaturated flow and transport model was modified to simulate the effects of non-linear air-water interfacial (AWI) adsorption, solution surface tension-induced flow, and variable solution viscosity on the unsaturated transport of per- and polyfluoroalkyl substances (PFAS) within the vadose zone. These modifications were made and completed between March 2019 and May 2019, and were implemented into both the one-dimensional (1D) and two-dimensional (2D) versions of HYDRUS. Herein, the model modifications are described and validated against the available literature-derived PFAS transport data (i.e., 1D experimental column transport data). The results of both 1D and 2D example simulations are presented to highlight the function and utility of the model to capture the dynamic and transient nature of the temporally and spatially variable interfacial area of the AWI (Aaw) as it changes with soil moisture content (Θw) and how it affects PFAS unsaturated transport. Specifically, the simulated examples show that while AWI adsorption of PFAS can be a significant source of retention within the vadose zone, it is not always the dominant source of retention. The contribution of solid-phase sorption can be considerable in many PFAS-contaminated vadose zones. How the selection of an appropriate AawΘw function can impact PFAS transport and how both mechanisms contribute to PFAS mass flux to an underlying groundwater source is also demonstrated. Finally, the effects of soil textural heterogeneities on PFAS unsaturated transport are demonstrated in the results of both 1D and 2D example simulations.

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“… a Perfluorinated carbon chain length. b Measured diffusion coefficient by Schaefer et al c Theoretical diffusion coefficient determined by the Hayduk-Laudie equation …”

Section: Introductionmentioning

confidence: 99%

Facing the Challenge of Poly- and Perfluoroalkyl Substances in Water: Is Electrochemical Oxidation the Answer?

Radjenović

Duinslaeger

Avval

et al. 2020

Environ. Sci. Technol.

142

103

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Electrochemical treatment systems have the unique ability to completely mineralize poly-and perfluoroalkyl substances (PFASs) through potential-driven electron transfer reactions. In this review, we discuss the state-of-the-art on electrooxidation of PFASs in water, aiming at elucidating the impact of different operational and design parameters, as well as reported mechanisms of PFAS degradation at the anode surface. We have identified several shortcomings of the existing studies that are largely limited to smallscale laboratory batch systems and unrealistic synthetic solutions, which makes extrapolation of the obtained data to real-world applications difficult. PFASs are surfactant molecules, which display significant concentrationdependence on adsorption, electrosorption, and dissociation. Electrooxidation experiments conducted with high initial PFAS concentration and/or in high conductivity supporting electrolytes likely overestimate process performance. In addition, the formation of organohalogen byproducts, chlorate and perchlorate, was seldom considered. Nevertheless, the first step toward advancing from laboratory-scale to industrial-scale applications is recognizing both the strengths and limitations of electrochemical water treatment systems. More comprehensive and rigorous evaluation of novel electrode materials, application of scalable proof-of-concept studies, and acknowledgment of all treatment outputs (not just the positive ones) are imperative. The presence of PFASs in drinking water and in the environment is an urgent global public health issue. Developments made in material science and application of novel threedimensional, porous electrode materials and nanostructured coatings are forging a path toward more sustainable water treatment technologies and potential chemical-free treatment of PFAS-contaminated water.

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Measurement of Aqueous Diffusivities for Perfluoroalkyl Acids

Cited by 37 publications

References 23 publications

A Mathematical Model for the Release, Transport, and Retention of Per‐ and Polyfluoroalkyl Substances (PFAS) in the Vadose Zone

A Mathematical Model for the Release, Transport, and Retention of Per‐ and Polyfluoroalkyl Substances (PFAS) in the Vadose Zone

A Modified HYDRUS Model for Simulating PFAS Transport in the Vadose Zone

Facing the Challenge of Poly- and Perfluoroalkyl Substances in Water: Is Electrochemical Oxidation the Answer?

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