In-situ Sequestration of Perfluoroalkyl Substances Using Polymer-Stabilized Powdered Activated Carbon
By Chen Liu, James Hatton, William A Arnold, Matt Francis Simcik, Kurt D Pennell
May 12, 2020
Remediation of groundwater impacted by per- and polyfluoroalkyl substances (PFAS) is particularly challenging due to the strength of the carbon-fluorine bond and the need to achieve extremely low drinking water health advisory levels. Previous studies have shown that activated carbon is an effective sorbent for removal of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in conventional water treatment systems. The objective of this study was to evaluate the delivery and sorptive capacity of an aqueous suspension containing powdered activated carbon (PAC) stabilized with polydiallyldimethylammonium chloride (polyDADMAC). Batch reactor studies demonstrated substantial adsorption of PFOA and PFOS by 100-mesh Darco® PAC, with maximum capacities of 306 mg/g and 340 mg/g, respectively. In columns packed with 40-50 mesh Ottawa sand, injection of a PAC (1,000 mg/L) + polyDADMAC (5,000 mg/L) suspension created a sorptive region that increased subsequent PFOA and PFOS retention by three orders of magnitude relative to untreated control columns, consistent with the mass of retained PAC. Experiments conducted in a heterogenous aquifer cell further demonstrated the potential for stabilized-PAC (S-PAC) to be an effective in situ treatment option for PFAS-impacted groundwater.