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Evaluation of a Solidification/Stabilization Process for PFAS Contaminated Soils
Citation:
Barth, E., J. McKernan, D. Bless, D. Cutt, S. Hartzell, AND K. Dasu. Evaluation of a Solidification/Stabilization Process for PFAS Contaminated Soils. PNLL DOE REMPLEX Summit, N/A, N/A, November 08 - 12, 2021.
Impact/Purpose:
This study evaluated the addition of a sorbent to PFAS contaminated soil samples and then evaluating the addition of cement to physically immobilize the soil. The presentation will discuss the results and other issues.
Description:
PFAS contaminated sites remedy decisions may involve the consideration of some form of a containment technology such as an in-situ immobilization process. A bench-scale study involving granular activated carbon (GAC), an activated carbon-clay blend, modified clay, biochar, and an iron (Fe)-amended biochar were evaluated as a potential sorbent for use in an in-situ stabilization/solidification process. In addition to sorbent addition, physical solidification of the contaminated soil was achieved by adding cement as a binding agent. Results from the initial sorption experiments indicated that GAC was slightly more effective than the other sorbents in sorption performance for a 3,000 µg/L solution containing a mixture of the six selected PFAS analytes (500 µg/L concentration each of shorter- and longer-chain alkyl acids), and was the only sorbent further evaluated in the immobilization study. While the GAC, activated carbon-clay blend, and modified clay sorbents showed similar sorption performance for the longer chain analytes tested, both the activated carbon-clay blend and modified clay, exhibited slightly less sorptive capacity than GAC for the shorter-chain alkyl acids. Immobilization effectiveness was evaluated on soils obtained from two PFAS contaminated sites by soil leachability testing using the Environmental Protection Agency’s Method 1312, Synthetic Precipitation Leaching Procedure (SPLP). For the majority of the detected PFAS soil analytes, the addition of GAC sorbent (chemical stabilization) substantially reduced the leachability of PFAS compounds from the contaminated soil samples, and the addition of cement as a physical binding agent (solidification) further decreased leachability for many of the PFAS compounds. Overall immobilization of PFAS analytes that were detectable in the leachate from two PFAS contaminated soils ranged from 87.1% to 99.9%. Therefore, it may be reasonable to consider that the laboratory testing results may have application to further pilot or limited field scale studies within a broader suite of PFAS contaminated site treatment options that are currently available for addressing contaminated soils.