(79a) Superfine Activated Carbon-Functionalized Adsorptive Thin-Film Nanocomposite Membranes for Selective Pfas Removal from Water

Due to the widespread production and use of per- and poly-fluoroalkyl substances (PFAS), as well as their ability to move and persist in the environment; surveys conducted by the Centers for Disease Control and Prevention (CDC) show significant human exposure to PFAS. The membrane filtration and adsorption process are the two main effective separation and removal methods for PFAS removal from water, where each technique possesses a unique capability. Thin-film composite (TFC) nanofiltration (NF) membranes showed an acceptable (<90%) removal of PFAS. However, the presence of rejected PFAS in the concentrate stream needs another separation process. In this study, we report the fabrication of adsorptive thin-film nanocomposite (TFN) NF membranes functionalized with super fine ( <100 nm) activated carbon (SFAC) for enhanced perfluorooctanesulfonic acid (PFOS) removal by adsorption during the water filtration. The NF membrane was fabricated on a poly (ether sulfone) (PES) support layer with a polyamide (PA) selective layer functionalized by immobilization of AC inside the PA via interfacial polymerization. The isotherm adsorption of SPAC showed 93% removal of PFOS in DI water. The bare NF membrane showed 12 (L.m^-2.h^-1.bar^-1) water permeability, around 60% NaCl rejection, more than 99% salt MgSO4 rejection, and 90% PFAS removal. The functionalized SFAC-TFN membranes, showed similar PFOS removal, but the dominant mechanism appeared to be adsorption instead of rejection. SFAC-TFN-0.5 membranes (the TFN membrane functionalized with the optimal amount of 0.5 wt.% SFAC) showed a PFOS removal of 94 %, with more than 80% being adsorption and an increased permeability of 22 (L.m^-2.h^-1.bar^-1) compared to the bare TFC. The rejection of PFOS in presence of humic acid is also observed to study the selectivity of PFOS on the adsorptive membrane. In addition, the SFAC-TFN-0.5 showed acceptable re-generability without sacrificing the membrane performance.