Analyzing the Release of Per- and Polyfluoroalkyl Substances from Spent Granular Activated Carbons by Standard Leaching Procedures

Abstract

The recent national primary drinking water regulation for per- and polyfluoroalkyl substances (PFAS) is expected to drive a nationwide increase in granular activated carbon (GAC) usage in water treatment facilities across the United States. Proper management of PFAS-laden GAC waste streams is essential to prevent potential recontamination. This study systematically evaluates PFOA and PFOS leaching from four commercial GACs using three standard batch leaching procedures. Our findings indicate that PFOA leached 1–2 orders of magnitude more than PFOS across all GAC types and leaching procedures. In general, PFAS leaching was more notable for alkaline leaching conditions, especially for wood-based GAC. Additionally, real groundwater spiked with an 8 PFAS mixture was used to load GAC for leaching propensity demonstration, and similar conclusions were reached, where leaching was generally greater for shorter-chain and more hydrophilic PFAS. PFBA exhibited the highest leaching (10.4%), followed by GenX (0.91%) and PFBS (0.75%), while minimal desorption (<0.02%) was observed for long-chain PFOA, PFOS, PFOSA, and PFNA. The study concluded that a complex interplay of multiple interactions between the GAC surface, PFAS molecules, and constituents of leaching solutions controls leaching.