Per- and polyfluoroalkyl substances (PFASs) continue to pose substantial risks to environments and human health, making effective treatment approaches a priority. Using strongly basic water at temperatures and pressures near the critical point, hydrothermal alkaline treatment (HALT) has been shown to completely degrade and mineralize PFASs in water and aqueous soil slurries. Here, we have extended the application of HALT for treatment and potential regeneration of granular activated carbon (GAC) sorbents contaminated with PFASs. Mass balance experiments, where a predetermined mass of perfluorooctane sulfonate (PFOS) was pre-loaded onto GAC prior to treatment, showed that HALT achieved &gt;99% removal of PFOS and &gt;96% defluorination after treatment. Experiments conducted with field-spent GAC obtained from a recent pilot study also demonstrated effective treatment of a wide range of perfluoroalkyl acids, including both PFOS and perfluorooctanoic acid (PFOA). Similar adsorption isotherms for PFASs were measured for virgin and HALT-treated GAC, indicating that adsorption properties were retained following treatment. It follows that HALT may be an alternative to conventional off-site thermal regeneration.

Regeneration potential of spent granular activated carbon using hydrothermal alkaline treatment (HALT) for the destruction of adsorbed PFASs

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