Green sorption media for the removal of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) from water

This study investigated the removal of selected per- and polyfluoroalkyl substances (PFAS) from water via two green sorption media (IFGEM-7 and AGEM-2). Both selected green sorption media recipes contain sand (85-91%) and clay (3-4%), in addition to recycled iron (Fe) (5-7.5%) or aluminum (Al) (4.5% in AGEM-2 only). Batch and column studies were integrated and performed using the prescribed green sorption media recipes to determine their efficiencies in removing two most targeted PFAS, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). In the batch test, while the removal efficiencies of PFOS ranged from 27 to 46% and 23 to 42%, those for PFOA ranged from 6 to 16% and 5 to 18% when using IFGEM-7 and AGEM-2, respectively. The higher removal of PFOS than PFOA observed in both IFGEM-7 and AGEM-2 batch tests could be attributed to higher media affinity for sulfonate groups of PFOS when compared to the carboxylate groups of PFOA. In the column study, the initial removal (within 1 h) by IFGEM-7 was greater than 99% for PFOS and 28% for PFOA. When comparing different dynamic adsorption models, it appears that the non-linear equations could better describe the trend of experimental data compared to the linear forms of the Modified Dose Response model. Life expectancy calculations, performed for demonstration purposes of field applications, suggested that if IFGEM-7 were to be applied in a downflow filter box to treat a hypothetical volume of 60,000 L of water during an emergency response, and it may last for 1506 h (62.8 d) and 4.2 h for a target removal of 80% of PFOS and PFOA, respectively.