Conference on Environmental Science and Technology

This study investigated the regeneration of PFAS-laden granular activated carbons (GACs) by microwave (MW) irradiation. Two commercially available GACs (bituminous coal based GAC [BCGAC] and lignite coal based GAC [LCGAC]) were saturated with perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) and then irradiated at different MW conditions. The performance of MW regeneration for PFAS-saturated GACs was assessed by evaluating the variation of GAC adsorption capacity (regeneration efficiency, RE) and weight loss percentage (WL). Moreover, the effect of MW irradiation on GAC textural properties (e.g., surface area and pore volume) was examined through N2 adsorption isotherms. Additionally, five successive ad- sorption/regeneration cycles were carried out at the MW operational condition that allowed to reach the target temperature (T > 600 °C) while minimizing the WL. Both GACs exhibited a strong ability to convert MW irradiation into a rapid temperature increase (~150 °C min −1 at 500 W). The highest values of RE ( > 90%) for both PFOA- and PFOS-saturated GACs were obtained at MW irradiation conditions that employed short regeneration time (3 min) and optimal temperature. Indeed, the highest RE did not occur at the highest temperatures ( > 750 °C) due to the damage of GAC porous structure, particularly for LCGAC. After five cycles, the observed values of RE (~65%) and a moderate weight loss ( < 7%) demonstrated the good performance of MW irradiation for regenerating PFOA- and PFOS-saturated BCGAC. Defluorination of PFAS during microwave regeneration of PFAS-laden GACs was also investigated. Under the optimal conditions (653 ◦C/min, 65–70 % moisture), fluoride recovery ranged from 91–99 % for PFOA, PFOS, PFBA, and PFBS-laden GACs. The obtained findings pointed out that MW irradiation is a promising alternative regeneration technique for PFAS-laden GAC that reach over 90 % PFAS defluorination.