Supercritical CO2 Regeneration of Spent Ion Exchange Resins and Regenerant Destruction -- Towards Zero PFAS Waste

Per- and polyfluoroalkyl substances (PFAS) are commonly removed from wastewater matrices using ion-exchange resins (IXRs). This practice generates PFAS-laden solid waste, requiring disposal of spent sorbent and introducing long-term liability. We demonstrate a closed-loop strategy for treating spent macroporous and gel-type sorbents that integrates supercritical CO2 (scCO2)-enabled regeneration with end-of-life regenerant treatment. The scCO2-amended with ethanol and HCl achieves rapid and near-complete regeneration of PFOA-loaded resins, RE% = 99.7 ± 0.1% at T = 75°C and a 60 min contact time, without compromising their structure or surface functional groups, thus enabling repeated adsorption-regeneration cycles. The PFAS-rich regenerant is then fully mineralized in a continuous-flow supercritical water oxidation (SCWO) system, where the regenerant's chemical energy enables the reactor's autogenic operation, eliminating secondary waste streams. Integrating rapid PFAS extraction and downstream PFAS destruction enables the reuse of IXR sorbents and reduces treatment costs, material consumption, and long-term environmental liability in PFAS remediation.