Journal of Membrane Science最新文献

In the present work, a series of crosslinked polybenzimidazole (PBI) anion exchange membranes (AEMs) were prepared via the vinyl-based in-situ crosslinking method. The crosslinked AEMs (PcPBI-x-C) had simultaneously improved dimensional stability, mechanical properties and chemical stability compared to the pre-crosslinked AEM (PcPBI). The effect of different crosslinker structures including rigid benzene ring, flexible alkanes and flexible alkanes containing hydrophilic imidazolium on the performance of AEMs was systematically investigated. As results, the swelling ratio of the PcPBI-Vbc-C membrane containing rigid benzene ring crosslinked structure was reduced by 49.8 % (from 22.1 % to 11.1 %), the tensile strength of PcPBI-Im-C membrane containing flexible hydrophilic imidazolium crosslinked structure increased by 33.5 % (from 48.1 MPa to 64.2 MPa) and the elongation at break by 115.2 % (from 28.9 % to 62.2 %). PcPBI-x-C crosslinked AEMs had conductivities of 87.6–98.7 mS/cm at 80 °C, their conductivity retentions were 72.5–82.4 % after immersion in 2 M KOH solution for 2400 h. Furthermore, the anion exchange membrane water electrolysis (AEMWE) with PcPBI-Im-C as AEM could be stably operated for 100 h at the current density of 200 mA/cm², indicating that PBI AEMs containing flexible hydrophilic imidazolium crosslinked structure possess great potential for application in AEMWE.

To develop highly conductive membranes for VRFB, triphenyl quaternary phosphonium cationic groups were introduced into unique adamantane-containing poly(aryl ether ketone) to prepare TAPEK membranes. The selective swelling-induced microphase separation strategy was also adopted to strengthen membrane conductivity. The quaternary phosphonium groups give the membrane the Donnan repulsion effect, so the TAPEK membrane exhibits low area resistance and a good barrier to cross-mixing vanadium ions. The TAPEK-100 membrane exhibited a low area resistance of 0.12 Ω cm⁻², lower than the current state-of-the-art Nafion212 membrane (0.14 Ω cm⁻²). TAPEK membranes were used for VRFB for the first time, and the TAPEK-100 exhibited excellent energy efficiency in VRFB (EE=91.0 % at 80 mAcm⁻², EE=85.1 % at 200 mAcm^−2, EE=80.36 % at 280 mAcm⁻², and EE=79.32 % at 300 mAcm⁻²). TAPEK membrane showed insufficient stability in in-situ and ex-situ stability tests. The battery efficiency of VRFB with TAPEK-90 membrane dropped significantly after more than 823 cycles in the cycling test. Given the high conductivity of TAPEK membranes, more work related to enhancing the stability of quaternary phosphonium groups-containing membranes needs further study.

Coupling photocatalysis with membrane separation technology becomes one pioneering method to solve the membrane fouling. In this study, Ag@SnS photocatalyst was synthesized and blended with polyvinylidene fluoride (PVDF) to fabricate Ag@SnS/PVDF composite membranes via non-solvent induce phase separation (NIPS) method. The results show that with the addition of Ag@SnS, water flux of Ag@SnS/PVDF hybrid membranes increases due to the enhanced membrane hydrophilicity and increased porosity. The optimal hybrid membrane (MAS-2) exhibits the rejection rate of 97.0 % and 95.4 % for BSA and HA accompanied with a water permeance of 578.5 L m⁻² h⁻¹ bar⁻¹. Moreover, MAS-2 membrane reveals excellent self-cleaning ability by photodegradation of HA on membrane surface, and its flux recovery rate (FRR) can achieve 91.7 % after UV irradiation and 95.8 % after 3 h natural sunlight irradiation via photocatalysis regeneration. The heterostructure of Ag@SnS can assist separation of photoinduced electrons and holes by transferring photoinduced electrons to Ag nanoparticles with enhanced photocatalytic activity. After three cycles, the FRR can still reach around 90.0 %, revealing its outstanding cleaning ability. Therefore, the Ag@SnS/PVDF membranes have a foreseeable potential in the field of water treatment due to its high flux performance, self-cleaning ability via photocatalysis process.

It is well known that crosslinking poly(ethylene oxide) (PEO) membranes exhibit high CO₂/N₂ solubility selectivity, and are suitable for separating CO₂ from flue gas. However, the high CO₂/N₂ selectivity is temperature sensitive and decreases rapidly with increasing temperature. To overcome this deficiency, imidazolium-based amino acid ionic liquids (AAILs) are introduced into the PEO membranes. A series of (AAILs-PEO)/PAN thin-film composite (TFC) membranes were prepared by a polymerization-induced self-assembly process. Due to the hydrogen and Coulomb interactions between the imidazolium ring of AAILs and the ether groups of PEO monomers, the morphology of the selective layer changed from micellar to granular upon the introduction of the AAILs into the PEO membranes, while the chain-segment flexibility and interspacing of the PEO are also changed. Compared with the original PEO/PAN TFC membrane, the (AAILs-PEO)/PAN TFC membranes show much higher CO₂/N₂ selectivity, which increases from ∼41 to ∼ 74. In addition, the AAILs show strong hydrophilicity, which leads to a significant increase in CO₂/N₂ selectivity under the wet-gas feed, reaching ∼105. Compared with the original PEO/PAN TFC membranes with CO₂/N₂ selectivity of ∼10 at 70 °C, the (AAILs-PEO)/PAN TFC membranes show the selectivity of ∼30, coupled with CO₂ permeance of ∼1300 GPU at 70 °C. Under the 40: 60 mixtures of CO₂: N₂, which is a common lime kiln exhaust gas, by using the (AAILs-PEO)/PAN TFC membrane, the CO₂ concentration on the downstream side can reach over 90 % at 20 °C and over 70 % at 70 °C, respectively, under a pressure ratio of 5.

The optimal operating temperature for contemporary perfluoro-sulfonic acid (PFSA)-based proton exchange membranes (PEMs) is identified to range from 60 to 80 °C. However, operating at temperatures exceeding this threshold could offer substantial advantages. Therefore, the development of PEMs that can maintain performance at elevated temperatures is imperative. This study introduces novel SUS composite proton exchange membranes with a three-layer architecture. These membranes feature a central UIO-66-NH${}_2$/Nafion composite layer (U), bordered by sulfonated carbon-nanotubes/Nafion composite layers (S) on both sides. The SUS PEMs demonstrate improved proton conductivity, long-term stability, fuel cell efficiency, and gas barrier properties. Notably, at the elevated temperature of 145 °C, attributable to enhanced water retention capabilities, these membranes exhibit significant proton conductivity, reaching 0.428 S cm⁻¹. For fuel cell evaluations, the SUS PEMs exhibited optimal performance (0.940 W cm⁻²) at the elevated temperature of 115 °C. These improvements are attributed to the dense S layer, which regulates diffusion rates of both water and gas molecules, and the U layer, which serves as a water reservoir due to its high retention capacity. These conclusions have been validated through computational simulations and further supported by positron annihilation spectroscopy.

To tackle the challenges of phosphoric acid (PA) leakage and suboptimal proton transfer efficiency in PA-polybenzimidazole (PBI) high-temperature proton exchange membranes (HTPEMs), this research has pioneered the development of a novel porous silicon material, DP/S15, which has been tailored through organic phosphonic acid modification. S15 or DP/S15 was utilized to fabricate PBI composite membranes and subjected these membranes to a thorough examination of their properties. The integration of DP/S15 into the membrane matrix notably enhanced acid uptake and facilitated the formation of a robust and extensive proton transportation network. This was largely attributable to the synergistic interaction between the organic phosphonic acid groups in DP/S15 and PA. As a result, the membranes incorporating DP/S15 exhibited a host of commendable properties, most notably their substantial mechanical strength, which registered at 89.80 MPa with undoped PA and 13.10 MPa with doped PA. Furthermore, theoretical analyses lent credence to the efficient adsorption between DP/S15 and phosphoric acid. Consequently, the composite membranes delivered superior performance metrics, evident in their high conductivity (reaching 57.7 mS cm⁻¹ at 160 °C) and excellent PA retention capabilities (up to 89.5 %). Of paramount significance was the performance of the single fuel cell equipped with the PA-DP/S15-PBI composite membrane, which achieved a peak power density of 672.29 mW cm⁻². This figure impressively surpassed that of the pure PBI membrane by 262.23 mW cm⁻². In light of these promising outcomes, the PA-DP/S15-PBI composite membrane harbors significant potential for deployment in HT-PEMFCs.

Metal organic framework (MOF)-polymer composite solid electrolyte membrane with novel microstructure is expected to show attractive prospect for solid state lithium metal batteries. But the reported MOF were usually regarded as an entirety in composite solid electrolyte resulting in tradeoff between ionic conductivity and lithium dendrite inhibition ability. Herein, MOF-polymer composite membrane with vertically aligned channels and ultrathin MOF layer is proposed to decrease lithium ion transportation resistance obtained by simple phase inversion and in situ coordinated growth methods. The vertically aligned highways can decrease tortuous pathways and intensify ion conduction. The embedded ultrathin MOF layer on membrane surface leads to homogeneous plating/stripping of lithium. This novel structured MOF-polymer composite solid electrolyte exhibits improved ionic conductivity of 0.55 mS cm⁻¹ at 22 ° C and lithium ion transference number of 0.87. Furthermore, the Li/Li symmetrical cell shows stable lithium plating/stripping performance for 1100 h at 0.1 mA cm⁻² and 0.1 mA h cm⁻². LiFePO₄/MOF-polymer/Li coin battery demonstrates good rate capability and cycling performance with capacity retention of 82 % after 100 cycles at 0.2C and the pouch cell can light up the “DLUT” blue light lamp under folding and cutting states. This work encourages a new avenue to develop composite solid electrolytes with ion transportation highways and uniform distribution plane for solid lithium metal batteries.

The management of hypersaline brine is a critical challenge to achieving a circular water economy. Traditional brine treatment technologies mainly rely on thermal evaporation, which requires intensive energy, cost, and/or areal footprint. Electrodialytic crystallization (EDC) has been recently developed as a novel process that enables brine crystallization without evaporation. However, the potential effects of mineral scaling and organic fouling on the performance of EDC have not been revealed. In this study, we systematically investigated mineral scaling and organic fouling in EDC. We demonstrate that the ion transport and crystallization efficiencies of EDC are generally unaffected by a variety of mineral scalants and organic foulants, despite an increase of energy consumption in the presence of humic acid. Further, EDC is shown to be less susceptible to gypsum scaling than RO, mainly due to the difference in concentration polarization between these two membrane processes. To mitigate gypsum scaling in an assumptive EDC-RO treatment train towards zero liquid discharge (ZLD), polyacrylic acid (PAA) is employed as an antiscalant that prevents gypsum scaling in RO while not adversely affecting EDC performance at relatively low concentration. Our study unravels the behaviors of EDC when treating feedwater with high scaling and fouling potentials, providing valuable insights for understanding mineral scaling and organic fouling when applying an ED-based technology for hypersaline brine treatment towards ZLD.

Preferred orientation control represents a crucial step for performance enhancement of MOF membranes. Nevertheless, their sustainable preparation remains a significant challenge. In this work, we fabricated highly (110)-oriented ZIF-8 membranes through supercritical fluid (SCF)-assisted epitaxial growth of oriented seed layer. Benefiting from unique physicochemical properties and intrinsic chemical inertness of supercritical CO₂, preferential orientation originated from the seed layer could be well maintained during epitaxial SCF processing; moreover, both unreacted ligands and discharged CO₂ could be efficiently recovered, resulting in zero pollutant emission. Our ZIF-8 membrane exhibited ideal C₃H₆/C₃H₈ selectivity of 91.8. To the best of our knowledge, this represented the first report of the preparation of highly oriented ZIF-8 membrane with such high C₃H₆/C₃H₈ selectivity; more importantly, our study demonstrated that SCF processing represented an effective protocol for orientation modulation of MOF membranes towards superior separations.