Investigation of an immobilization process for PFAS contaminated soils

Area of Science:

• Environmental Engineering
• Geochemistry
• Remediation Technologies

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants.
• In-situ solidification/stabilization (ISS) is a potential treatment for PFAS-contaminated soils.
• Effective sorbent materials are crucial for the chemical stabilization phase of ISS.

Purpose of the Study:

• To evaluate sorbent materials for chemical stabilization of PFAS in soils.
• To assess the combined effectiveness of sorbent treatment and cement solidification for PFAS immobilization.
• To determine the applicability of laboratory findings to field-scale remediation.

Main Methods:

• Phase 1: Bench-scale sorption experiments using six PFAS compounds and five sorbents (GAC, activated carbon-clay blend, modified clay, biochar, Fe-amended biochar, Ottawa sand).
• Phase 2: Chemical stabilization with the most effective sorbent (GAC) followed by cement solidification of two PFAS-contaminated soils.
• Immobilization effectiveness evaluated via EPA Method 1312 Synthetic Precipitation Leaching Procedure (SPLP).

Main Results:

• Granular activated carbon (GAC) demonstrated superior sorption performance for a mixture of short- and long-chain PFAS compared to other sorbents.
• GAC treatment significantly reduced PFAS leachability from contaminated soils.
• Cement solidification further decreased leachability for some PFAS compounds, with overall immobilization ranging from 87.1% to 99.9%.

Conclusions:

• GAC is a viable sorbent for the chemical stabilization of PFAS-contaminated soils.
• The combination of GAC and cement offers a promising approach for in-situ PFAS immobilization.
• Results support further pilot or field-scale studies for PFAS-contaminated site remediation.