Granular activated carbon (GAC) filters are widely used to treat PFAS-contaminated waters. Although GAC works very well for the removal of long-chain PFAS (carbon chain length ≥ C7), the removal of short chain PFAS (&lt;C7) is short-lived due to their low hydrophobicity, and as a result their breakthrough occurs early from GAC columns. Furthermore, the sorption of short-chain PFAS is strongly influenced by the presence of co-contaminants, including the presence of long-chain PFAS. In this study, we performed controlled batch adsorption experiments to understand the competition between short- and long-chain PFAS for sorption onto F400 GAC (Calgon Carbon). Since GAC filtration is also commonly combined with advanced oxidation processes (AOPs) and coagulation/flocculation systems for removal of PFAS, we additionally evaluated the impacts of residual oxidants (H2O2) and polymers (PolyDADMAC and/or CPAM) typically employed in AOPs and coagulation processes, respectively, on the uptake process of PFAS. Our result indicates that sorption of short-chain PFAS was significantly suppressed by the presence of long-chain PFAS, and the effect was more prominent at elevated concentration. Our ongoing research is further studying the impact of co-existing H2O2 and cationic polymers on the sorption of PFAS using a combination of batch and column (RSSCT) experiments.

Competition between short-chain and long-chain per- and polyfluoroalkyl substance (PFAS) during sorptive removal by granular activated carbon

ACS Fall 2021

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