Ionic and pH responsive thin film composite hollow fiber nanofiltration membrane for molecular separation

Ionic and pH responsive thin film composite (TFC) membrane is prepared by interfacial polymerization of lysine and trimesoyl chloride on the out surface of poly (m-phenylene isophthalamide) hollow fiber membrane. Hydrophilicity and strong negative charge of the TFC membrane are obtained by introducing a large amount of carboxylic groups in the cross-linked polyamide network, endorsing the ionic and pH response of the TFC membrane in terms of flux and rejection. The TFC membrane shows almost 100% rejection for Eriochrome black T, with a flux of 35.8 L/m2h (0.2 MPa) at low pH and salt concentration. However, the rejection decreases to 95.8%, and the flux increases more than three times at high pH and salt concentration due to the shift of the interaction in the polyamide network from hydrogen bonding to static-electric repulsion. The responsive TFC membrane also shows great performance in separation of dye-salt mixture and dye mixture.