Competitive adsorption of PFAS on granulated activated carbon and ion exchange resins: Effects of co-existing PFASs, DOM, and phosphate

Effective removal of per- and polyfluoroalkyl substances (PFAS) form contaminated waters remains a significant treatment challenge in remediation facilities due to their structural heterogenicity, high aqueous mobility, and frequent occurrence as complex multi-component mixtures. Although granular activated carbon (GAC) and ion exchange resins (IER) are widely used for PFAS treatment, their performance is strongly influenced by water-matrix composition and competitive adsorption among PFAS, which can accelerate breakthrough and reduce adsorption capacity. Consequently, treatment performance assessments and capacity estimates may remain uncertain under multi-component conditions. Accordingly, this study evaluates how structurally diverse PFAS compete during adsorption and displacement in single- and multi-solute systems. This unified comparison clarifies how GAC and IER chemistry influence PFAS competitive behavior. Coexisting organic and inorganic constituents, dissolved organic matter (DOM) and phosphate, were incorporated to simulate realistic water matrices and to quantify their influence on PFAS competition and displacement. Results revealed that PFAS chain length and functional group chemistry governed the competitive hierarchy, with sulfonates generally exhibiting greater surface stability and removal efficiency than carboxylates. In addition, the results demonstrated distinct surface-dependent competitive behavior across the studied sorbents. GAC exhibited pronounced inhibition and displacement of PFAS in the presence of dissolved organic matter, whereas IER maintained relatively higher selectivity toward PFAS but was more susceptible to phosphate-induced displacement, highlighting the distinct matrix sensitivities of the two sorbents. These findings provide critical insight into PFAS treatment in multi-component systems and emphasize the importance of water-matrix specific design considerations to improve treatment efficiency, particularly for short-chain PFAS.