High-performance nanofiltration of outer-selective thin-film composite hollow-fiber membranes via continuous interfacial polymerization

• Outer-selective thin film composite membrane was synthesized via continuous interfacial polymerization. • The processing parameters were optimized to obtain the defect-free thin film composite membranes. • The water flux reached 48 LMH/bar with salt rejection of 99.6%. Outer-selective thin film composite (TFC) hollow fiber membranes have the advantages of fiber blockage with less pressure drop and high surface area module. This work highlights novel strategies to design continuous interfacial polymerization that can allow mass production, performance controllability, and small margin of error in performance. Processing parameters were symmetrically optimized to maximize high water flux and salt rejection using poly(piperazine-amide) TFC membranes. For further improving the membrane performance, polyvinyl alcohol was incorporated for an interlayer, thereby having the water flux of 48 LMH/bar and the salt rejection (Na 2 SO 4 ) of 99.6%. The system can be used in a variety of applications such as reverse osmosis, forward osmosis, or gas separations by simply replacing the monomers.