High Adsorption Pearl-Necklace-Like Composite Membrane Based on Metal-Organic Framework for Heavy Metal Ion Removal

The zeolitic imidazolate framework-67 (ZIF-67)-based pearl-necklace-like composite membranes are prepared by in situ intergrown on the surface of 2-methylimidazole/cellulose acetate (MIM/CA) electrospun nanofibers for the first time. With the aid of MIM, the ZIF-67 nanocrystals successfully grow throughout the composites and attach to the fibers just like the pearls in necklace. The incubation time of ZIF-67 has a significant influence on the structures and properties of the composites. And with an approximate saturation of ZIF-67 nanocrystals, the integrated composites achieve a much higher surface area of 463.1 m2 g(-1), which is as dozens of times as that of pure MIM/CA electrospun nanofibers (6.9 m2 g(-1)). In addition, the composites performed a high Cu(II) and Cr(VI) adsorption of 18.9 mg g(-1) and 14.5 mg g(-1), respectively. The adsorption data are well fitted with the pseudo-second-order kinetics. Moreover, adsorption mechanism is also discussed, and the electrostatic adsorption and ions exchange contribute to the high adsorption of Cu(II) and Cr(VI), and the existence of Cr(III) indicates that the Cr(VI) ions are partially reduced to Cr(III) during the adsorption. Therefore, the fabricated metal organic framework-composite membrane with special pearl-necklace-like is a promising environmental material for removing heavy metal ions from water.