Enhanced water permeance of a polyamide thin-film composite nanofiltration membrane with a metal-organic framework interlayer

Constructing an interlayer between porous substrate and polyamide (PA) film is an effective strategy to overcome the ubiquitous trade-off between permeability and selectivity, which are both important properties for nanofiltration performance. In this study, a poly(sodium 4-styrenesulfonate) (PSS) assisted interfacial synthesis method was proposed to fabricate a zeolitic imidazolate framework-8 (ZIF-8) interlayer between the PA film and microporous poly(ether sulfone) (PES) membrane. The addition of PSS to Zn2+ containing aqueous solution was able to stabilize the ZIF-8 layer formed at the water/n-hexane interface and benefited the homogeneous loading of ZIF-8 on the substrate with effective coverage of the macrovoids. The surface of ZIF-8 loaded PES membrane became smoother and more negatively charged, providing improved conditions for interfacial polymerization to form a thin, loose, and defect-free PA film. The pure water permeance of the TFC membrane containing modified ZIF-8 interlayer was 9.6 L m-2 h-1·bar-1, twice that of the pristine TFC membrane. Meanwhile, its rejection of sodium sulfate, rhodamine B, and acid fuchsin was well maintained. The introduction of ZIF-8 interlayer via the PSS assisted interfacial synthesis method was a promising technique to fabricate high-performance NF membrane for water treatment.