Mixed-matrix membranes (MMMs) for CO 2 /N 2 separation were prepared by incorporating nickel-substituted ZIF-8 (Zn/Ni-ZIF-8) into a polyether-block-amide (PEBA2533) polymer, in which the Zn and Ni ions in Zn/Ni-ZIF-8 have different affinities for CO 2 based on π-complexation; these MMMs exhibited exceptional molecular sieving properties compared to ZIF-8-PEBA MMMs. Scanning electron microscopy revealed that Zn/Ni-ZIF-8 nanoparticles were small and uniformly distributed within the PEBA, and attenuated total reflectance Fourier-transform infrared spectroscopy revealed good interfacial compatibility between the Zn/Ni-ZIF-8 and PEBA; consequently these MMMs exhibited excellent mechanical properties . The 10% Zn/Ni-ZIF-8-PEBA MMM showed a high CO 2 permeability of 321 Barrer, and a CO 2 /N 2 selectivity of 42.8 at 2 bar; these values were much higher than those of the 10% ZIF-8-PEBA MMM (266 Barrer and 33.8, respectively). We assume that different metal-ion affinities towards CO 2 resulted in the asymmetric adsorption/desorption behaviour of these MMMs, which led to a significantly higher permselectivity for the Zn/Ni-ZIF-8-PEBA MMM. The MMM loaded with 10% Zn/Ni-ZIF-8 exhibited long-term CO 2 -separation-performance stability under mixed-gas conditions, with a CO 2 permeability of 282 Barrer and a CO 2 /N 2 selectivity of 42.7. Moreover, the permselectivity of the 10% Zn/Ni-ZIF-8-PEBA MMM under pure-gas condition surpassed Robeson's upper bound reported in 2008.
Yang Zhang,Siru Zhou,Zhenglei Li,Haoquan Zhang,Meng Zhang,Jun Wang,Lingling Chen,Hongwei Zhang
Pore forming agent or hydrophilic additives are necessary for the optimization of membrane pore structure and surface physicochemical properties. Although it has been demonstrated that the blending additives tends to locate around membrane pore walls due to segregation and this would further leach out in practical operations, the impact of additives fate on membrane pore structure as well as sieving performance is almost overlooked in literatures. In this study, five kinds of Pluronic copolymers with different molecular architectures were employed for casting PSF UF membranes, and the fate of these copolymers in membrane matrix was explored by combing FTIR and XPS spectra with TG analysis . More importantly, the evolutions of membrane mean pore radius (r*) and radius distribution (σ) after additive leaching were quantitatively investigated based on the modified Steric Pore Model (SPM). In passive solute sieving experiments, the increment of r* and σ possessed positive correlation with the degree of polymerization (DP) of EO segments within the corresponding additive. The results of thermoporosimetry and saline filtration experiments further evidenced that such a correlation should be attributed not only to the steric hindrance of EO segment, but also to its hydration ability. Moreover, the intrinsic polymer geometry (r ST ) was also a crucial factor for understanding the evolutions of membrane pore structure during additive leaching. Especially for membranes having small r ST , both the isopropanol (IPA) treatment and poly-dopamine (PDA) decoration experiments suggested that pore enlargement and the generation of new small cavities would occur simultaneously during additive leaching, making the prediction complicated. Finally, we proposed that the relative synthetic aperture (RSA) could serve as a complementary indicator for understanding and describing the pore enlargement behavior of a blended UF membrane. In an industrial point of view, it also offers a new way to evaluate and predict the long-term performance and stability of a blending modified porous membrane.
The efficiency of the hemodialysis membrane has been widely improved by blending small molecular additives and modifying the membrane surface for patients with chronic or acute kidney disease. However, a qualified sieving property, flux, and hemocompatibility are intractable to give consideration simultaneously, while the elution of small-molecular additives and modifiers easily cause coagulation, complement activation, etc. Fortunately, the BCP methoxy polyethylene glycol-polyethersulfone-block-methoxy polyethylene glycol (mPEG -b- PES -b- mPEG) based membranes exhibiting great potential for sieving in middle molecular toxin and compatibility between mPEG -b- PES -b- mPEG and PES, is nearly unfeasible elution during hemodialysis, by reason of including bounded hydrophilic segments by chemical bonds. Here, the mPEG -b- PES -b- mPEG is synthesized to fabricate the membranes, including blend membranes and BCP membrane. As a result, the blend membranes have shown an increasing flux, hemocompatibility, and sieving of lysozyme with the increasing cooperation of mPEG-b-PES-b-mPEG, the block copolymer (BCP) mPEG -b- PES -b- mPEG membrane has shown better balance than the blend membranes in flux, sieving, and hemocompatibility. Besides, for exploring further possibilities, the typical blend membrane M4 (mPEG- b -PES- b -mPEG: 20%, PES: 5%) and BCP membrane M5 (mPEG- b -PES- b -mPEG: 25%) are post tailored by ethanol at 50 °C for 2 h. This process leading the typical membranes to an efficient flux (M5-P: 442.22 L m −2 h −1 ) and sieving performances (M5-P: the urea and lysozyme sieving of 96.43% and 74.97%) due to the effect of ethanol at the micro-molecular chain movements and microspheres transfer. Our work presents BCP mPEG -b- PES -b- mPEG a promising future in hemodialysis membranes according to the superior performances of flux and sieving.
危险品化学品经营许可证（带存储）