Remediation of PFAS-Contaminated Soil and Granular Activated Carbon by Smoldering Combustion

This study explored smoldering combustion for remediating polyfluoroalkyl substance (PFAS)-impacted granular activated carbon (GAC) and PFAS-contaminated soil. GAC, both fresh and PFAS-loaded, was employed as the supplemental fuel supporting smoldering in mixtures with sand (≈175 mg PFAS/kg GAC-sand), with PFAS-spiked, laboratory-constructed soil (≈4 mg PFAS/kg soil), and with a PFAS-impacted field soil (≈0.2 mg PFAS/kg soil). The fate of PFAS and fluorine was quantified with soil and emission analyses, including targeted PFAS and suspect screening as well as hydrogen fluoride and total fluorine. Results demonstrated that exceeding 35 g GAC/kg soil resulted in self-sustained smoldering with temperatures exceeding 900 °C. Post-treatment PFAS concentrations of the treated soil were near (2 experiments) or below (7 experiments) detection limits (0.0004 mg/kg). Further, 44% of the initial PFAS on GAC underwent full destruction, compared to 16% of the PFAS on soil. Less than 1% of the initial PFAS contamination on GAC or soil was emitted as PFAS in the quantifiable analytical suite. Results suggest that the rest were emitted as altered, shorter-chain PFAS and volatile fluorinated compounds, which were scrubbed effectively with GAC. Total organic fluorine analysis proved useful for PFAS-loaded GAC in sand; however, analyzing soils suffered from interference from non-PFAS. Overall, this study demonstrated that smoldering has significant potential as an effective remediation technique for PFAS-impacted soils and PFAS-laden GAC.