Enhanced removal of perfluorooctane sulfonic acid and perfluorooctanoic acid via polyelectrolyte functionalized ultrafiltration membrane: Effects of membrane modification and water matrix

[Display omitted] •PAH/PAA modification resulted in membrane MWCO and porosity reductions.•30 % increase in PFOS and PFOA removal compared to unmodified UF due to size exclusion.•Coexistence of cations and HA caused significantly higher removal of PFOS and PFOA.•Size/charge exclusion of PFOS-cation-PFOS, PFOS-cation-HA, PFOA-cation-HA complexes. This study investigated the mechanisms of removal of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) using polyelectrolyte (PE) functionalized ultrafiltration (UF) membranes, performed through a fluidic method of layer-by-layer (LbL) deposition of polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) multilayer coatings. The effects of source water composition (humic acids [HA] and cations [Ca2+ and Mg2+]) on PFOS and PFOA removal efficiency by the functionalized membrane were determined. PAH/PAA modification resulted in approximately 38 % and 9.2 % reduction in membrane molecular weight cut-off (MWCO) and porosity, respectively, leading to approximately 30 % increase in the removal of PFOS and PFOA primarily due to size exclusion. The presence of only HA led to 10–12 % higher removal of PFOS/A when compared to DI water; however, an increase in HA concentration did not further influence their removal efficiency. The coexistence of cations and HA resulted in significantly higher removal of PFOS and PFOA (up to 23 % higher for PFOS). Further enhancement of PFOS removal (14 % higher) was observed when cation concentrations were doubled, attributable to the interactions of PFOS/A with the source water components and the functionalized membrane, resulting in enhanced size and charge exclusion of macromolecular complexes including PFOS-cation-PFOS, PFOS-cation-HA, and PFOA-cation-HA.