Abstract

Soils contaminated with per- and polyfluoroalkyl substances (PFASs) are an important source for impacting drinking water delivery systems and surface water bodies world-wide, posing an urgent risk to human health and environmental quality. However, few treatment techniques have been tested for PFAS-contaminated soil hotspots. This study investigated the possibility of thermal desorption as a possible technique to remediate soils contaminated with multiple PFASs. Two fortified soils (∑9PFAS ≈ 4 mg kg-1) and one field-contaminated soil (∑9PFAS ≈ 0.025 mg kg-1) were subjected to a 75-min thermal treatment at temperatures ranging from 150 to 550°C. Soil concentrations of PFASs showed a significant decrease at 350°C, with the ∑9PFAS concentration decreasing by, on average, 43% and 79% in the fortified and field contaminated soils, respectively. At 450°C, >99% of PFASs were removed from the fortified soils, while at 550°C the fraction removed ranged between 71 and 99% for the field contaminated soil. In the field contaminated soil, PFAS classes with functional groups of sulfonates (PFSAs) and sulfonamides (FOSAs) showed higher removal than the perfluoroalkyl carboxylates (PFCAs). Thus thermal desorption has the potential to remove a wide variety of PFASs from soil, although more studies are needed to investigate the cost-effectiveness, creation of transformation products, and air-phase vacuum filtration techniques.

Highlights

  • Per- and polyfluoroalkyl substances (PFASs) are a large group of partially or completely fluorinated organic compounds that vary in structure and chemical properties and are generally persistent to thermal, chemical, and biological degradation [1, 2]

  • Comparing the fortified clay and loamy sand soils, at 350 ̊C perfluoroalkyl carboxylates (PFCAs) and FOSA were removed to >99%, while the PFAS classes with functional groups of sulfonates (PFSAs) showed removal ranging between 51% (PFHxS) and 66% (PFOS)

  • Previous studies have shown that PFSAs are more strongly sorbed than PFCAs to soil and sediments [49,50,51], which might result in lower desorption potential for PFSAs

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Summary

Introduction

Per- and polyfluoroalkyl substances (PFASs) are a large group of partially or completely fluorinated organic compounds that vary in structure and chemical properties and are generally persistent to thermal, chemical, and biological degradation [1, 2]. Concerns have been raised because of their ubiquitous distribution in the environment, high persistency, bioaccumulation potential, and adverse effects on humans and biota [3,4,5,6,7,8]. A common point source is the unregulated usage of PFAS-containing aqueous film-forming foams (AFFFs) at firefighter. Thermal desorption as a high removal remediation technique for soils contaminated with PFASs

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