Perfluoroalkyl substances (PFAS) are known as forever chemicals in the water system. Utilities are using granular activated carbons (GACs) to remove the PFAS from the water system. Used GACs are reusable to remove PFAS upon regeneration of GAC. But current conventional techniques (i.e., thermal and chemical regeneration) are not economically feasible to regenerate PFAS-exhausted GAC because those methods decrease the capacity of GAC. While regenerating GAC, it is necessary to keep their adsorption capacity retained/intact. Here, a new technique (microwave (MW) irradiation) was used to regenerate PFAS-exhausted GAC. Two commercially available coal-based GACs were saturated with perfluorobutanoic acid (PFBA), perfluorooctanoic acid (PFOA), perfluorobutane sulfonic acid (PFBS), and perfluorooctane sulfonic acid (PFOS) and then irradiated at different MW conditions. The performance of MW regeneration for selected PFAS-saturated GACs was assessed by evaluating the variation of GAC adsorption capacity (regeneration efficiency, RE) and weight loss percentage (WL). Five successive adsorption/regeneration cycles were carried out at the MW operational condition that allowed to reach the target temperature (T&gt;600 °C) while minimizing the WL. For PFOA- and PFOS-saturated GACs, the highest values of RE were obtained at MW irradiation conditions that employed a short regeneration time and optimal temperature. Indeed, the highest RE did not occur at the highest temperatures (&gt;750 °C) due to the damage of the GAC porous structure. After five cycles, the observed values of RE (~65%) and a moderate weight loss (&lt;7%) demonstrated the good performance of MW irradiation for regenerating PFAS saturated. The obtained findings pointed out that MW irradiation is a promising alternative regeneration technique for PFAS-saturated GAC.

Regeneration of PFAS-exhausted granular activated carbons by microwave irradiation

ACS Fall 2021

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