Per- and polyfluoroalkyl substances (PFASs), used since the 1940s, are persistent
and carcinogenic pollutants. Water is a major exposure route; effective removal is
essential. While nanofiltration (NF) and reverse osmosis (RO) are effective but costly,
ultrafiltration (UF) membranes offer advantages such as lower cost and higher flux,
but their relatively large pore size makes them ineffective for PFAS compounds like
perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Since PFAS
removal depends on both pore size and surface properties, this study investigates
the effect of polyelectrolyte multilayer coatings using poly(allylamine hydrochloride)
(PAH) and poly(acrylic acid) (PAA) on the zeta potential of UF membranes. Pristine
UF membranes showed limited performance (UP150: ~2% for both PFOS and PFOA; UP020:
34.4% PFOS, 24.1% PFOA), while coating significantly enhanced removal (coated UP150:
45.3% PFOS, 43.4% PFOA; coated UP020: 77.8% PFOS, 73.3% PFOA). The modified UF membranes
achieved PFAS removal efficiencies significantly closer to NF membranes, though still
below those of RO (e.g., BW30XLE: up to 91.0% PFOS, 88.3% PFOA; NP030: up to 81.0%
PFOS, 79.3% PFOA). Findings emphasize the importance of membrane surface charge and
suggest that modified UF membranes offer a promising, low-cost alternative for PFAS
removal under low-pressure conditions.
