Development of MXene-Based Nanofiltration Membranes With Improved Hydrophilicity and Separation Performance via Tannic Acid/PEI Crosslinking

This study developed a novel thin-film nanocomposite (TFN) membrane using vacuum-assisted deposition and surface chemical crosslinking by integrating MXene nanosheets with a tannic acid (TA) and polyethyleneimine (PEI) crosslinked network onto a PVDF substrate. A series of tests were conducted to characterize the chemical structure and surface morphology of the membranes, as well as to measure the concentrations of dye wastewater and saline solutions before and after filtration. The results showed that the introduction of the phenol-amine network altered the surface properties of the MXene layers, reducing the water contact angle to 49.8° and resulting in a negative zeta potential in the pH range 4–10. The optimized TFN-2 membrane achieved 100% removal of cationic dyes (methylene blue, malachite green, crystal violet), with rejection rates of 98.52%, 97.12%, and 100% for methylene blue, Congo red, and Coomassie brilliant blue G, respectively, and also exhibited certain salt ion rejection capability. Moreover, the introduction of the phenol-amine network significantly enhanced the oxidative stability of MXene. The TFN-2 membrane maintained stable flux and removal efficiency during 12 h of continuous operation and retained excellent separation performance after 90 days of storage. This study provides a new approach for developing high-performance separation membranes.