Remediation of per- and polyfluoroalkyl substances contaminated soil using air-driven fluidized-bed non-thermal...

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants that pose significant ecological and human health risks. This study investigated the effectiveness of a fluidized-bed non-thermal plasma (NTP) system for the remediation of PFAS-contaminated soils, in which compressed air serves as the working gas to sustain the discharge and fluidize the soil particles, enabling direct plasma-soil interaction under atmospheric pressure. Seven representative PFAS compounds, including legacy perfluorocarboxylic acids (PFCAs, C5-C9) and novel hexafluoropropylene oxide (HFPO) oligomer acids (HFPO-DA and HFPO-TA), were evaluated to achieve effective removal performance in an environmentally friendly and cost-efficient manner. Under optimized conditions, the plasma system achieved high removal efficiencies, with near-complete removal of long-chain PFCAs and substantial removal of HFPO oligomers. Machine learning analysis using Extreme Gradient Boosting (XGBoost) indicated that working gas composition was the most influential factor in PFAS removal. Integrated mechanistic investigations, including optical emission spectroscopy, radical scavenging experiments, and density functional theory (DFT) calculations, clarified that e^-, OH•, and NO₂• act as the primary reactive species responsible for C-F bond cleavage. Moreover, the Ecological Structure-Activity Relationship (ECOSAR) model predicted lower acute toxicity and reduced bioaccumulation factor for most degradation products relative to the parent compounds. These findings demonstrate the potential of fluidized-bed plasma systems as an efficient and environmentally friendly strategy for remediating PFAS-contaminated soils.