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

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.