| Zeolitic Imidazolate Framework-8 (ZIF-8) was synthesized in methanol with 2-methylimidazole as an organic linker and Zn (NO3)2 as metal ions source at room temperature. The structure and formation process of ZIF-8 were characterized by FTIR, XRD, TEM and TG. The results showed that ZIF-8 crystals were formed at the initial stage quickly, and they gradually grew up to form hexagon and dodecahedron in 3D. A fundamental understanding of ZIF-8 structural evolution would facilitate the preparation of functional metal-organic framework phases with controlled crystal size and morphology.TFC membranes with ZIF-8 were prepared by interfacial polymerization of TMC and PIP with dispersing ZIF-8 nanoparticles in PIP aqueous phase. The special wetability, surface charge and porosity of ZIF-8 have great influence on interfacial polymerization of polyamide and influence the property of NF membrane. The effects of ZIF-8 concentration on Na2SO4 rejection and water flux of TFC membranes were studied. The surface morphology and chemical structures of composite membranes were observed by scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier Transform infrared spectroscopy (FTIR). Resistance to chlorine and thermal stability of the membrane were also studied.The separation data showed that 0.02 (w/v%) membrane modified with ZIF-8 presented highest performance in terms of the rejections of Na2SO4 was 98.7%, and water flux was increased to 46.2 L/m2.h at 0.6 MPa. EDS of membrane cross-section showed that the thickness of polyamide film was about 80 nm. By comparing the Zn mapping of TFC membranes, illustrated that adding 0.05 (w/v%) ZIF-8 produced a slight aggregates on the surface of membrane and the aggregates were become more seriously as adding 0.5 (w/v%) ZIF-8. Moreover, this high performance remained stable for long-term testing during 600 min and even temperature reaching to 70℃. |
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