Preparation of <scp>PPTA</scp>/<scp>PA</scp>/<scp>PEMs</scp> Composite Nanofiltration Membranes With Multilayer Structure for Thermal Wastewater Treatment

ABSTRACT In this study, a multilayer PPTA/PA/PEMs composite nanofiltration (NF) membrane was fabricated through sequential processes. First, a polyamide (PA) separation layer was constructed on a Poly (p‐phenylene terephthamide) (PPTA) substrate via interfacial polymerization (IP). Subsequently, polyacrylamide hydrochloride (PAH) and polystyrene sulfonic acid (PSS) were alternately deposited on the PA layer using layer‐by‐layer (LBL) assembly, forming polyelectrolyte multilayers (PEMs). The PAH‐terminated membrane (M4.5) demonstrated 97% retention for CaCl 2 and 98% for methylene blue (cationic dye) at 25°C, while the PSS‐terminated membrane (M3) achieved 98% retention for Na 2 SO 4 and 97% for eosin Y (anionic dye) under identical conditions. Thermal stability tests across 25°C–65°C revealed retention rates exceeding 90% for M3and M4.5. Prolonged operation of M4.5 with CaCl 2 solution at 65°C for 80 h resulted in minimal efficiency loss, confirming robust thermal resistance. This performance is attributed to the synergistic combination of the thermally stable PPTA and the multilayer‐engineered PA‐PEMs structure, which effectively suppresses pore deformation under thermal stress. This study presents a novel preparation strategy for heat‐resistant composite NF membranes, demonstrating exceptional application potential in the treatment of conventional textile dyeing and printing wastewater under high‐temperature conditions.