Journal of Membrane Science最新文献

Mono-valent selective ion-exchange membrane, as the core component of selective electrodialysis (SED), has received extensive attention. In this work, we report a mono-valent selective anion-exchange membrane (AEM), which was fabricated with distorted poly(aryl ether sulfone) and decorated with bifunctional side-chains providing anion exchange groups and hydrophobic segments. By tuning the length of the hydrophobic side-chains, the nanophase separation within AEMs was finely tuned, evidenced by an ionic cluster size of about 0.47 nm from SAXS analysis. The optimized AEM (PAES-TA-7 AEM) shows a very low water swelling ratio of 6.4 %, signaling good dimensional stability. The perm-selectivity ($P_{{SO}_4^{2–}}^{{Cl}^{–}}$) of PAES-TA-7 AEM during ED reached 107 at 2.5 mA∙cm⁻² (ion flux: 2.69 × 10⁻⁸ mol cm⁻² s⁻¹ at 90 min) significantly exceeding that of the commercial Neosepta ACS (11; 2.08 × 10⁻⁸ mol cm⁻² s⁻¹). It is inferred that the ion channels, resulting from nanophase separation between the side-chains and the backbone, as well as the free volume cavity created by the distorted backbone, significantly contribute to the smooth transport of the Cl⁻ ions through the AEM with less resistance. As a result, it is believed that this work offers a useful strategy to advance the monovalent anion-selective membranes.

Amine-rich facilitated transport membranes (FTMs) attract great interest in intensifying the membrane-based CO₂ separation processes. The high-molecular-weight polyvinylamine (PVAm) polymers containing fixed-site carriers of the amino groups were used to prepare highly CO₂-permeable membranes. The sterically hindered PVAm polymers of poly(N-methyl-N-vinylamine) and poly(N-isopropyl-N-vinylamine) were obtained by functionalization of PVAm to provide superior CO₂ solubility. By loading the mobile carriers of amino acid salt (AAS) and CO₂-philic graphene oxide (GO), the prepared FTMs render enhanced CO₂ permeance and CO₂/N₂ selectivity. The d-spacing of 8.8 Å and the ultramicropores of 3.5 Å from GO nanosheets provide the combination of both selective surface flow and molecular sieving mechanisms to achieve improved CO₂ permeance and CO₂/N₂ selectivity. In addition, the intercalation of GO hinders N₂ transport through the membrane due to a longer pathway, while the mobile carriers of AAS introduced into the PVAm matrix facilitate CO₂ transport through the selective layer. Therefore, the CO₂/N₂ selectivity of the prepared FTMs was significantly enhanced to 171 based on the intensified carrier-driving transport mechanism. It can be concluded that amine-rich membranes based on both fixed and mobile carriers of the amino groups together with intercalated GO can synergistically improve the CO₂/N₂ separation performance, and be potentially applied for CO₂ capture from flue gas.

Aqueous organic redox flow batteries (AORFBs) have become a promising electrochemical energy storage technology due to their low cost, high safety, and sustainability. As key components of emerging AORFBs, membranes face challenges such as scarcity of available membranes and high prices. Moreover, currently available membranes have low battery performance because these membranes are not optimized for specific AORFBs. In this work, a new cation exchange membrane sulfonated anthrone-containing poly(aryl ether ketone) (SAnPEK) membrane was prepared for the first time and achieved significantly improved performance in (SPr)₂V/K₄[Fe(CN)₆] AORFBs. SAnPEK membrane has excellent selectivity and high mechanical strength (>50 MPa). SAnPEK membranes exhibit high conductivity in 1 M NH₄Cl solution. For example, SAnPEK-4 membranes exhibit low surface resistance (0.176 Ωcm²) in 1 M NH₄Cl solution, which is significantly better than Nafion117 (1.02 Ωcm²) and Nafion212 membranes (0.276 Ωcm²). SAnPEK membrane exhibtis impressive performance in (SPr)₂V/K₄[Fe(CN)₆] AORFB. The SAnPEK-4 membrane exhibits high coulombic efficiency (CE) and excellent energy efficiency (EE) (CE = 99.1 %, EE = 83.4 % at 100 mAcm⁻²), and the EE for SAnPEK-4 membrane is significantly better than that for the Nafion117 membrane (CE = 99.3 %, EE = 62.4 %) and Nafion212 membrane (CE = 99.1 %, EE = 80.8 %, 100 mAcm⁻²). In addition, the SAnPEK-4 membrane exhibits excellent cycle stability over 3000 cycles in AORFB. As a high-performance, easy-to-prepare, low-cost cation exchange membrane, SAnPEK membranes have good application potential in AORFBs.

In this study, various electrospun and electrosprayed fibrous membranes from polyethersulfone (PES) and polyvinylpyrrolidone (PVP) were fabricated, to which a common solvating extractant tri-n-octylphosphine oxide (TOPO) was incorporated. Such TOPO-involved PES membranes were attempted to selectively clear p-cresol, one of trace amounts of small uremic toxins, from simulated serum via hydrogen bonding. Morphological and physicochemical properties of the as-synthesized fibrous membranes were first studied. Batch tests displayed that the equilibrium of p-cresol adsorption on all fibrous membranes were attained within 2 h. Analysis of adsorption isotherms of p-cresol by the Langmuir equation revealed that the adsorption was improved in the presence of TOPO; moreover, the distribution state of TOPO powders along the fibers played an important role in membrane performance. Among the six as-prepared TOPO-incorporated membranes, the highest adsorption capacity of p-cresol in simulated serum at 37^oC and pH 7.4 reached to be 21.7 mmol per gram of TOPO. The operational stability of as-prepared fibrous membranes was evaluated by checking their adsorption ability, membrane weight, water contact angle, structural changes by SEM imaging, and PVP dissolution using UV–Vis spectroscopy, both before and after exposure to PBS solution. Crossflow permeation-adsorption of a multicomponent mixture (0.46 mmol/L of p-cresol, 1.33 mmol/L of creatinine, and 38.3 mmol/L of urea) for 4 h indicated that the prepared membranes yielded a high selectivity toward p-cresol against creatinine and urea of 21.2–43.0 and 10.8–18.5, respectively. Hemolysis tests and viability measurements of both human umbilical vein endothelial cells and THP 1 monocytic leukemia cells demonstrated that the proposed configurations of the TOPO-incorporated fibrous membranes were hemo- and bio-compatible. Our results on the composition and systematic design of these fibrous membranes suggested that they can serve as an advanced hemoperfusion unit, maintaining high p-cresol removal and bio-compatibility. These well-designed membrane-based devices could be connected in series with the conventional hemodialysis devices to further improve the overall removal of small uremic toxins.

Nanofiltraion (NF) membranes are promising candidates for overcoming critical global issues of access to clean water. However, current NF membranes are hampered by the trade-off between the water permeability and selectivity as well as the fouling propensity. In this work, a facile surface decoration simultaneously combined with solvent activation strategy was adopted for the NF membrane modification via simply immersing membrane into the polyoxometalates (POMs) ethanol solution. The introduction of POMs by coordination assembly increases the membrane hydrophilic and electronegativity, and the ethanol loosens the membrane selective layer, leading to the enhanced membrane perm-selectivity and anti-organic fouling property. The permeance and Na₂SO₄ rejection of the optimized modified NF membrane are 14.90 ± 0.21 LMH/bar and 99.20 ± 0.38 %, which are ∼20 % and more than 3 % increments compared with those of the control membrane, respectively. The modified NF also reveals a lower permeance decline as well as a higher flux recovery toward both positive and negative charged foulants. In addition, benefiting from the biocidal activity of the POMs, the membrane anti-biofouling property is also significantly improved under an extremely low loading of POMs. More importantly, the chemical stability of the modified NF membrane is reinforced due to the protection from the introduced POMs. Our work contributes to revitalizing the prospect of developing NF membranes with excellent filtration performance and antifouling property.

Sterile filtration is one of the critical steps in the production of lipid nanoparticle (LNP)-based biotherapeutics. However, LNP fouling can limit the overall capacity of the sterilizing-grade filter. Effective design and control of this unit operation enables a robust manufacturing process. The objective of this study was to examine the sterile filtration of mRNA-LNP through the dual-layer Sartopore 2 XLG membrane during both constant flux and constant transmembrane pressure (TMP) filtration experiments. The complete pore blockage model effectively described the fouling behavior at constant TMP, with the rate of pore blockage decreasing with increasing TMP. However, a novel modification of the complete pore blockage model was needed to describe the fouling behavior during constant flux operation, with the rate of pore blockage found to be a function of both the instantaneous TMP and the TMP gradient. This new model successfully describes the TMP profiles during constant flux operation at multiple fluxes and the flux profiles during constant TMP operation at multiple TMPs, all using the same model parameters. These findings establish a foundational framework that mathematically describes the fouling behavior of mRNA-LNP and can be used to design and optimize sterile filtration processes for this class of biotherapeutic.

Two-dimensional (2D) materials-based membranes with artificial transfer channels have shown significant potential for selective separation. However, the challenges such as uncontrollable interlayer spacing and undesirable molecular sieving capabilities of 2D channels have impeded their further application in separation. Inspired by biological selectivity transport channels with proper steric and affinity sites, herein we have designed biomimetic 2D selective transport channels based on a ZIF-L nanosheet membrane. In this design, the UiO-66-NH₂ nanoparticles tune the appropriate interlayer confinement and compensate for laminate framework defects of 2D selectivity transport channels, the artificial imprinting recognition sites establishes the essential chemical environment for specific separation. As a result, the obtained MOFs nanosheet based membranes with imprinted recognition sites (MN-IMs) exhibited enhanced permeation flux (J = 1.0847 × 10⁻³ and 1.0423 × 10⁻³ mg min⁻¹ cm⁻²) and permselectivity (α = 3.77 and 4.10), outperforming state-of-the-art similar technologies. Besides, the composite MOFs demonstrated good photoinduced self-recovery ability, which also enables MN-IMs to have long-lasting selective separation performance (the separation efficiency is 90.76 %) in the continuous separation process. This study introduces a novel design strategy for developing sophisticated 2D materials-based membranes and offers new insights into the precise separation of specific molecules.

The use of carbonized polymers has ushered in a new class of materials with profound implications for the gas separation industry. This study explored the transformation of polyvinylidene fluoride (PVDF) into microporous carbon structures coated onto ceramic substrates, enabling in situ growth of carbon molecular sieve (CMS) materials over hollow fibers. This material featured more robust CMS membranes than alumina and demonstrated exceptional capability in vital gas separations, particularly for CO₂/CH₄. This novel approach increased the selectivity for gases and exhibited remarkable aging resilience, so the material is a compelling candidate for high-performance gas separations. Furthermore, after 31 days, the weathered carbon dioxide membrane exhibited a slight permeability drift from 234.88 barrers to 195.35 barrers, while the CO₂/CH₄ ratio increased from 24.21 to 57.14, surpassing the Robeson 2008 upper bound. The PVDF-derived supported hollow fiber carbon membranes provide a blueprint for designing membranes for carbon capture. With the high packing density of the hollow fiber membrane and improved mechanical strength of the supported carbon membrane, this approach overcame the high fabrication costs and brittleness of other carbon membranes. In addition, the entire process for preparation of the PVDF carbon films is easily scaled up and has great potential for future practical application.

Dense metal membranes are widely studied due to their promising performance in hydrogen separation. In this work, the low-cost dense iron (Fe) hollow fiber membranes (FeHFMs) were developed via the phase inversion and high-temperature sintering method. By tuning the preparation conditions, two typical gas-tight hollow fibers referred to as the sandwich- and honeycomb-structured membranes were successfully synthesized. H₂ permeation behavior was well described by Sieverts equation based on the solution-diffusion mechanism. The sandwich-structured FeHFMs had an H₂ flux of up to 7.51 mmol m⁻² s⁻¹ when operated at a temperature of 850 °C. In comparison, the honeycomb-structured FeHFMs further enhanced the H₂ flux by a factor of 3.2 due to the optimized membrane morphology with only one single dense iron layer. The developed FeHFMs showed superior H₂ permeation stability in thermal shock tests (40 h) and long-term stability tests (120 h). This work also expanded the potential application horizons of the FeHFMs, which can be easily tailored into porous or dense structures by tuning the sintering conditions.

Recently, low-energy forward osmosis (FO) technology has been employed in the lithium concentration stage during the extraction of lithium from brine sources. The interlayer FO membrane is renowned for its exceptional structural characteristics; however, challenges remain in selecting suitable interlayer materials and exploring their control mechanisms on amine monomers. As interlayer materials, traditional 3D nanomaterials are prone to detachment, while traditional 2D materials without micropores can increase the transmission resistance of water molecules. This study introduces a novel FO membrane utilizing Zr-BTB nanosheets with 5.4 Å micropores as the interlayer material. Based on detection and simulation calculations, it was found that the increase in steric hindrance and interaction forces jointly slowed the diffusion of amine monomers in the presence of the Zr-BTB interlayer. This results in a thinner separation layer, facilitating water transport. The interlayer also plays crucial roles in preventing defective pore formation in the separation layer and assisting in intercepting salt ions. The Zr-BTB interlayer membrane exhibited a water flux of 29.14 L m⁻² h⁻¹ and a reverse salt flux of 0.16 g m⁻² h⁻¹, which are superior to those of many FO membranes reported in the field. The prepared membrane also has excellent performance in lithium concentration applications, and its separation mechanism was explored by MD simulations.