Controllable Preparation of Ppta/Pems/Ppy Composite Nanofiltration Membranes for Multi-Environmental Desalination Performance

Abstract

A PPTA/PEMs/PPy composite nanofiltration membrane was fabricated by layer-by-layer (LBL) assembly of polyelectrolyte multilayers [poly (allylamine hydrochloride)/poly (styrene sulfonate) (PAH/PSS)] on a porous Poly (p-phenylene terephthamide) (PPTA) ultrafiltration membrane, followed by chemical vapor deposition (CVD) of polypyrrole (PPy) using pyrrole (Py) and ferric chloride (FeCl3). Controlling PEMs layer count and charge properties enabled precise structural tuning. SEM, AFM, FTIR, contact angle, and zeta potential analyses confirmed enhanced surface microstructure, hydrophilicity, and charge characteristics in the composite membrane compared to the PPTA substrate. At three PEMs layers (PAH/PSS)3, the membrane demonstrated optimal desalination performance under 0.8 MPa, achieving high permeability and stable rejection rates (~2% decline after 10 hours) for 5g/L Na2SO4. Stability tests under harsh conditions (80°C, pH=2, pH=13) revealed minimal permeability loss while maintaining near-constant salt rejection. Compared to prior PPTA/PPy membranes, the PPTA/PEMs/PPy composite exhibited superior permeability (demonstrated a minimum enhancement of 18%) and rejection rates (>95% for divalent salts) in high-salinity wastewater, alongside robust thermal stability and chemical resistance. The PEMs interlayer enhanced structural integrity and charge distribution, forms a gradient pore structure integrated with the PPy surface layer, mitigating concentration polarization and fouling. These results highlight the membrane’s potential for treating saline wastewater under extreme thermal and pH conditions, offering a scalable design strategy for advanced nanofiltration systems in industrial desalination applications. The work provides critical insights into optimizing polyelectrolyte-assisted interfacial engineering for durable separation membranes.

Keywords: PPTA, PEMs, Chemical Vapor Deposition (CVD), Acid and Alkali Resistance, High-Temperature Resistance