Work

Towards Zero-Waste PFAS Treatment Train: Regeneration of Ion Exchange Resins in Supercritical CO 2 Coupled with Supercritical Water Oxidation

Year: 2026

Type: preprint

Abstract: Ion-exchange resins (IXRs) are often used to remove PFAS from aqueous matrices; however, spent media generate secondary waste that must be disposed of. We demonstrate a waste-treatment strategy that combines IXR regeneration in a supercritical carbon dioxide (scCO 2 ) environment followed by destruction of PFAS-containing regenerants via supercritical water oxidation (SCWO). Screening of co-solvent formulation showed that HCl-amended ethanol/water mixture effectively extracted PFOA from both macroporous and gel-type resins marketed for single use. Macroporous IXR maintained sorbent capacity over five adsorption-regeneration cycles. Further optimization identified conditions for solvent reduction: an EtOH/H 2 O/HCl regenerant yielded regeneration efficiencies of ~97.6% for the gel-type and 99.7% for the macroporous resins within 60 minutes at flow rates corresponding to 9 BV. Comparison of the regenerant’s water content provided insights into the regeneration mechanism, progressing via (i) ion exchange in an H 2 O-rich hydration layer at the IXR surface followed by (ii) PFOA transport in the scCO 2 /EtOH-rich gas-like bulk flow. Downstream SCWO treatment of the regenerant shows complete PFOA defluorination. This treatment train advances sustainable PFAS management by combining sorbent reuse, reduced demand for non-toxic organic solvents, and end-of-life treatment of concentrated PFAS residuals.

Source: ChemRxiv

DOI: 10.26434/chemrxiv-2026-kzxwg/v2