Improving PFAS Rejection by Ultrafiltration Membranes via Polyelectrolyte Multilayer Coating

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent, carcinogenic pollutants with water as a primary exposure route.
• Conventional methods like nanofiltration (NF) and reverse osmosis (RO) are effective but expensive for PFAS removal.
• Ultrafiltration (UF) membranes are cost-effective with high flux but generally ineffective for PFAS due to larger pore sizes.

Purpose of the Study:

• To investigate the impact of polyelectrolyte multilayer coatings on UF membrane performance for PFAS removal.
• To assess the modification of UF membrane surface properties, specifically zeta potential, using poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA).
• To evaluate the effectiveness of modified UF membranes as a low-cost alternative for PFAS remediation.

Main Methods:

• Modification of pristine UF membranes (UP150 and UP020) with polyelectrolyte multilayers (PAH/PAA).
• Characterization of membrane surface properties, including zeta potential.
• Testing PFAS removal efficiency using perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) as target contaminants.

Main Results:

• Pristine UF membranes exhibited low PFAS removal (e.g., UP150: ~2%, UP020: 24.1-34.4%).
• Coated UF membranes showed significantly enhanced PFAS removal (coated UP150: 43.4-45.3%, coated UP020: 73.3-77.8%).
• Modified UF membranes approached the performance of NF membranes, demonstrating improved efficacy for PFOS and PFOA removal.

Conclusions:

• Membrane surface charge plays a critical role in PFAS removal efficiency.
• Polyelectrolyte multilayer coatings effectively enhance UF membrane performance for PFAS removal.
• Modified UF membranes present a promising, economical low-pressure alternative for treating PFAS-contaminated water.