Tannic acid-metal interlayers enhance permeance and antibiotics/NaCl separation efficiency of polyamide nanofiltration membranes

The assembly of metal ions and phenols has been widely exploited for surface modification of materials. In this work, polyamide (PA) composite nanofiltration membranes with different types of tannic acid-metal (TA/M n+ ) interlayers were fabricated. TA/transition metal interlayers endowed the PA composite membranes with enhanced water permeability and improved separation of antibiotics from NaCl. Among various TA/M n+ -PA membranes, TA/Al 3+ -PA membrane possessed increased pore size, augmented surface roughness, and reduced negative potential, exhibiting the most outstanding performance with a high-water flux of 8.94 L·m −2 ·h −1 ·bar −1 (429 % enhancement compared to PA membrane) and an excellent selective factor of 9.75 (589 % improvement over the PA membrane) for ciprofloxacin (CIP) and NaCl, successfully breaking the trade-off between permeability and selectivity. Moreover, this membrane displayed 89.92 % Na 2 SO 4 rejection and 94.10 % CIP rejection in the CIP/Na 2 SO 4 mixture. In addition, the TA/M n+ -PA membranes presented superior anti-fouling ability compared to the PA membrane. This study aims to explore the effects of different TA-metal interlayers on the performance of PA composite membranes and the underlying mechanisms, thereby offering more effective guidance for the application of such interlayered composite membranes.