ZIF-8-incorporated thin-film nanocomposite (TFN) nanofiltration membranes: Importance of particle deposition methods on structure and performance

The incorporation of functional nanomaterials is a promising technique to enhance or develop novel material properties, such as improvement of permeability and selectivity related to water purification and reuse. Herein, ZIF-8 nanoparticles were used to prepare the thin-film nanocomposite (TFN) membranes via both two-step in situ growth and one-step blending interfacial polymerization (IP) methods. The primary purpose was to investigate specific effects of different preparation methods and ZIF-8 nanoparticles on the structure and properties of TFN membranes. The results show that ZIF-8 nanoparticles increased the negative charge, roughness, and hydrophilicity of the polyamide rejection layer. The effects of one-step blending method on the TFN membrane characteristics were limited as compared to the two-step in situ growth method. The effective incorporation of ZIF-8 nanoparticles into TFN membranes increased the water permeability of TFN-ZIF-0.64 to 20.8 ± 0.62 L·m−2·h−1·bar−1 and enhanced the Na2SO4 rejection to 94.2 ± 3.4%, which is approximately 1.3 times increase in water permeability and 8.0% rise in rejection than those of TFC membrane. Comparatively, two-step in situ growth ZIF-8-modified TFN membranes displayed ultrahigh rejection of typical anionic dyes, demonstrating superior NF performance.