PFAS Removal from Foam Fractionation Enhanced Soil Washing Leachate : Evaluation of Sedimentation, Coagulation and Flocculation

Sammanfattning

Per- and polyfluoroalkyl substances (PFAS) are a group of persistent pollutants. PFAS pose a significant risk to the environment and human health due to their low degradability and biomagnification factor. Remediation of PFAS-contaminated soils is particularly challenging, conventional treatment methods are often insufficient for complete removal and are associated with high economic costs. The aim of this study is to evaluate the use of sedimentation, the conventional coagulant (PAX XL 100) and the PFAS-specific flocculant (PerfluorAd) for the removal of particles and PFAS from soil washing leachate. Single-step foam fractionation enhanced soil washing was used to transfer PFAS into aqueous phases of foam and leachate. The generated leachate was treated using sedimentation, coagulation and flocculation where laboratory-scale experiments were conducted to evaluate removal efficiencies for the selected compounds. Samples were analyzed using ultra performance liquid chromatography. The results show that foam fractionation effectively removed PFAS from the soil to the foam, leaving a residual fraction in the leachate. Sedimentation alone had negligible effects on PFAS removal efficiency, suggesting that most compounds were present in dissolved form, but had moderate effects on particle removal. The addition of PAX XL 100 achieved near-complete removal of particles and a limited PFAS removal (≈18% for PFOS). The combination of PAX XL 100 and PerfluorAd resulted in a near-complete removal of PFOS (≈100%) and improved removal of PFHpA and PFHxS at different dosages. The findings of this study demonstrate that a multi-step treatment is required for an effective PFAS-remediation of contaminated soils. However, the generated sludge during the coagulation and flocculation process highlights the need for appropriate sludge management.