Mixed matrix membranes (MMMs) can significantly improve gas separation performance, but the type and state of the filler in the membrane matrix are key indicators for the development of MMMs. Therefore, in this work, 6FDA-DAM/ODA (1:1), metal–organic frameworks (MOFs) with different particle sizes (UiO-66 and UiO-66-NH2) were synthesized, and then MOFs were doped into 6FDA-DAM/ODA to prepare MMMs. The effects of the dopant materials and their particle sizes on the gas separation performance of the membranes were investigated by testing the permeability of the MMMs to H2, CO2, CH4, and N2. When the dopant material was UIO-66, the permeability and selectivity of MMMs for each gas were significantly improved compared with that of the original membrane; when the dopant material was 300 nm UIO-66-NH2 with a loading of 10 wt %, the permeability performance and the CO2/CH4 selectivity increased from 44.1 to 57.2 compared with that of the original membrane. The permeation performance for CO2, N2, and H2 and the selectivity for CO2/N2, H2/N2, and H2/CH4 were also significantly improved. In terms of comprehensive separation performance, doping 300 nm UiO-66-NH2 was better than doping 70 and 400 nm UiO-66-NH2 and also showed excellent performance in 50:50 (vol/vol) CO2/CH4 binary mixed gas separation. This work provides an idea for the fabrication of MMMs for high-performance gas separation.
Extra-corporeal membrane oxygenation (ECMO) systems can perform the roles of the human heart and lungs to realize extra-corporeal oxygenation of blood. This system mainly depends on the gas-blood exchange membrane, the quality of which impacts the oxygenation performance. Currently, the most widely used gas-blood exchange membrane is made of poly(4-methyl-1-pentene) (PMP) hollow fibers. However, plasma leakage often occurs during clinical applications, which decreases the oxygenation performance and the service life and may endanger the patient's life in serious cases. In this work, Hyflon AD/PMP hollow fiber composite membranes were prepared by coating Hyflon AD on the surfaces of PMP hollow fibers to form ultra-thin, dense layers. Compared the plasma leakage time of the composite membrane with that of the pristine PMP membrane, the Hyflon AD60 layer showed great improvement in anti-leakage performance. The Hyflon AD60/PMP hollow fiber composite membrane possessed lower platelet adhesion and protein adhesion than that of the PMP membrane, indicating better blood compatibility of the Hyflon AD60 membrane. Cytotoxicity experiments were conducted to further confirm the biosafety of Hyflon AD60 as a blood contact medical membrane material. Gas permeance and oxygenation performance of the Hyflon AD60/PMP hollow fiber composite membrane were tested to ensure gas exchange efficiency during the gas separation process. Therefore, the optimized Hyflon AD60/PMP hollow fiber composite membrane has potential for clinical use.
Membrane fouling can be efficiently mitigated by the vibration of the piezoelectric membrane stimulated by AC signals, but it is still a challenge to fabricate piezoelectric membranes with great efficiency, low energy-consumption, and no harm to the environment during its preparation. The present work provides a new approach to poly(vinylidene fluoride) (PVDF) membranes with piezoelectric properties by directly poling β-phase PVDF membranes using green diluents, which revealed better piezoelectric properties than poling α-phase PVDF membranes. Basically, absolute β-phase crystals of PVDF membranes were induced over thermally induced phase separation with the addition of Acetyl tributyl citrate (ATBC)/ionic liquid ([BMIM]PF6), which are regarded as green and environment-friendly diluents. To endow the piezoelectric property to the β-phase PVDF membrane, a poling process was necessarily conducted. The effect of the poling process on the membrane structure, morphologies, properties, and performances was investigated. Meanwhile, a vibration test for both of the poled and unpoled membranes was performed in an excitation of the alternating signal. The results demonstrated that the poling process positively endowed the piezoelectric property to the PVDF membranes. The membrane structure, morphologies, and performances of the membranes were also changed to some extent by the poling process. Additionally, filtrations of the poled membrane both with and without electrical signals were carried out to test their antifouling performance on the CaCO3 suspension system and BSA solution, respectively. It was observed that the stable flux of the membranes notably improved when subjected to an electrical AC signal. Thus, it depicted that the piezoelectric PVDF membrane directly poled from the β-phase possesses a promising antifouling performance due to its high piezoelectric vibration.
In this paper, modified membranes containing β-cyclodextrin (β-CD) and heparin coatings were prepared on the surface of poly-4-methyl-1-pentene (PMP) hollow fibrous membrane using the high strength adhesion of polydopamine (PDA). In this paper, β-CD was added to increase the hemocompatibility of the PMP hollow fibrous membranes and the stability of the heparin coating. The uniformity of the heparin coating with β-CD addition was better than that of the groups without β-CD. After seven days of saline rinsing, the surface of the modified membranes with β-CD addition still had a large amount of heparin present, which was more stable compared to the control group. After surface modification, the modified membrane changed from hydrophobic to hydrophilic. Importantly, the protein adsorption, platelet adhesion, and hemolysis rates of the modified membranes were significantly reduced compared with the pristine membranes. The APTT values were also significantly increased. The results showed that the modified membranes with the addition of β-CD had better hydrophilicity, can maintain the stability of heparin coating for a long time, and finally showed good hemocompatibility.
Abstract In this paper, ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate was the first time successfully utilized as single solvent in preparing the PVDF membrane with a good performance by N-TIPs method. The effects of quenching temperature and hydrophilic additive content on the morphology, permeability, and strength of the membranes were studied. All the prepared PVDF membranes were proved to be a pure β phase by FTIR and XRD, possessing a narrow pore size distribution. By adjusting quenching temperature and additive content, membranes with a flux of 383.2 L/m 2 h and concentrated pore diameter of 26 nm obtained.
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