Benchmarking of Commercial Reverse Osmosis and Nanofiltration Membranes for Ultrashort‐, Short‐, and Long‐Chain Perfluoroalkyl and Polyfluoroalkyl Substance Rejection

Reverse osmosis (RO) and nanofiltration (NF) processes are considered "best available technologies" by the US Environmental Protection Agency for perfluoroalkyl and polyfluoroalkyl substance (PFAS) remediation from water. While these processes are industry standard for applications such as desalination, commercial membranes are typically tailored to said applications, so different membrane products may show differing PFAS rejection behavior based on proprietary manufacturing methods or surface modifications. Additionally, there are limited studies reporting rejection trends of ultrashort-chain (USC) compared to short-chain (SC) and long-chain (LC) PFAS. This work benchmarks a total of 13 commercial RO or NF membranes for eight PFAS, spanning all size classes, under standardized conditions for rejection performance. A comparison of overall PFAS rejection across the membranes showed statistically significant differences in performance, indicating that membranes do not uniformly reject PFAS equally and highlighting the role of membrane chemistry on performance. A strong positive correlation between measured salt rejection and overall PFAS rejection was found. Lastly, USC and SC species were found to have similar rejection while LC species showed significantly higher rejection. These findings emphasize the importance of membrane selection when designing a system for PFAS remediation and provide new insight into PFAS rejection behavior relative to other species and salts.