Modeling PFAS Rejection by NF/RO Membranes: A Critical Review and Research Needs

Nanofiltration (NF) and reverse osmosis (RO) membranes are typically highly effective for the rejection of per- and polyfluoroalkyl substances (PFAS), but existing studies have primarily focused on a small subset of compounds. Since the properties of individual PFAS vary and the rejection characteristics of NF and RO membranes likewise vary, a model that can predict PFAS rejection by membranes with specific properties would give water treatment practitioners more confidence in knowing that their choice of membrane treatment today would be effective for other PFAS of concern in the future. In this review, the state of the science of NF and RO rejection models is discussed, along with the unique physicochemical aspects of membranes and PFAS that impact membrane rejection. Finally, research is recommended to advance the state of membrane transport modeling by combining mechanistic, statistical, and system-level modeling methods to achieve predictive models without onerous input requirements.