Advanced Membranes最新文献

Silica membranes have been successfully practiced for solvent dehydration and emerged as an exciting platform for gas separations (such as H₂/CO₂) due to their unique porous structures for molecular sieving, tunable chemistries, and excellent thermal and chemical stability. This review aims to provide a comprehensive update on the advancement of silica membranes for gas and liquid separations in the last decade. First, we summarize various techniques to fabricate membranes (particularly those at low temperatures) and describe the effect of processing parameters on the membrane structures. Second, penetrant transport mechanisms and molecular dynamic simulations are presented to elucidate the structure-properties relationship. Third, we highlight state-of-the-art silica membranes with promising separation properties for gases, vapors, and liquids and various engineering strategies to improve hydrothermal stability, production scalability, and separation performance. Finally, we provide perspectives on the future development of these membranes for practical applications.

Catalytic membrane reactors have the advantages of allowing the selective removal of products, avoiding the separation procedure of powder catalysts from the reaction mixture, intensifying the diffusion of reactants in the catalytic region, and integrating different reactions in one unit. Catalytic membrane reactors have been widely applied in the fields related to carbon peaking and carbon neutrality, including the capture and utilization of carbon dioxide, hydrogen production, and hydrogenation reaction. This review summarizes the design and fabrication of catalytic membrane reactors, with the focus on the capture and efficient utilization of carbon dioxide, hydrogen production and efficient liquid-phase hydrogenation. The design of membrane materials, catalyst materials and catalytic membranes, and the operation of catalytic membrane reactors are discussed respectively. Finally, the perspectives and future challenges of catalytic membrane reactors for carbon peaking and carbon neutrality are forecasted.

Because of the greenhouse effect, there is a pressing need to restrict and reduce CO₂ emissions. Post-combustion capture technology is a type of widely used technologies for CO₂ capture. Compared to the standalone CO₂ capture processes such as absorption and cryogenic separation, hybrid CO₂ capture processes demonstrate improved separation efficiency and capacity for the overall performance. Membrane separation is a great candidate for process hybridization with other CO₂ capture processes. Three categories of hybrid processes consisting of membrane technology, i.e., in-series, parallel and integrated configurations, have been applied for CO₂ capture. This paper mainly reviews the recent research progresses on the process development as well as the techno-economic analyses of the hybrid processes corresponding to these configurations. Furthermore, the perspectives on future directions of hybrid CO₂ capture processes are discussed to facilitate its research and practical applications.

With the development of membrane separation technology, some traditional separation and purification methods have been replaced by membrane technology. Compared to traditional method, the membrane method has the advantages of small footprint, low energy consumption, safe operation and high removal rate. At present, membrane degassing has become a crucial step in ultra-pure water production for semiconductor industries, and it is also used in ink bubble removal and various wastewater treatment. This paper summarizes the advantages of membrane degassing compared with other gas-liquid separation methods, and introduces polymeric membrane materials used for degassing and their merits and drawbacks. The greatest challenge encountered in membrane degassing is the resistance to wetting phenomenon. This paper provides solutions to wetting phenomenon, which increases the possibility of widespread application of membrane degassing technology and the adaptability of membrane degassing technology to more demanding use scenarios. Finally, the application scenarios of membrane degassing technology are summarized and future prespectives are provided.

Sustainable production methods for polymer membrane fabrication are gaining attention due to concerns about the toxicity of conventional fossil-derived solvents in the production process. In addition, the promotion of using chemicals from renewable source for synthesis processes among industries and researches has increased to decelerate resource depletion. As such, more benign and bio-renewable solvents, dihydrolevoglucosenone (Cyrene™) and 2-methyltetrahydrofuran (2-MeTHF), have been proposed as replacements for traditional fossil-derived solvents, n-hexane and dimethylformamide (DMF). In this work, a life cycle assessment (LCA) was employed to quantitatively evaluate the environmental impacts of using the aforementioned bio-renewable solvents versus fossil-derived solvents for fabricating 1 ​g of polymer membrane. The analysis adopted a cradle-to-gate perspective and assessed three endpoint impact categories: Human health, Ecosystems and Resources. Despite lower environmental impacts for producing bio-renewable solvents, using such solvents to fabricate membranes displayed a higher environmental impact score in all endpoint categories. This discrepancy was attributed to the lower yield of the membrane fabrication process when using bio-based solvents. This indicated that further work is needed to optimise membrane fabrication so that the benefits of using bio-based solvents can be maximised.

Polyethersulfone (PES) polymers are useful for a variety of membranes' bio-related applications. However, due to its failure to satisfy certain performance and biocompatibility standards, PES requires further surface modification. Herein, we report a facile and flexible method of PES membrane modification by combining the synthesis of silicon oxide nanoparticles grafted with polyvinylpyrrolidone (PVP) as hydrophilic macromolecules via reversible addition fragmentation chain-transfer polymerization (RAFT) and aminated polyethersulfone. The blending of polyethersulfone-modified membranes with SiO₂@PVP and aminated polyethersulfone results in a robust, hydrophilic, and biocompatible surface. This research work uniquely uses this strategy to stabilize the existence of the hydrophilic modifiers (SiO₂@PVP and aminated polyethersulfone) within the membrane matrix. Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) are used to analyze the prepared polymer brush and the modified membranes. The modified membranes demonstrate high pure water flux at 345 ​L ​m⁻² ​h⁻¹ and bovine serum albumin (BSA) rejection at 98 ​%. The prepared membranes also show favorable hydrophilicity with a contact angle of 46.8° compared with pristine polyethersulfone at 79°. Furthermore, the modified membranes demonstrate an acceptable degree of blood biocompatibility according to partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), and fibrinogen (FIB) concentration analysis. Based on inductively coupled plasma optical emission spectroscopy (ICP-OES), the silicon nanoparticle leaching in permeate is in a safe range. Accordingly, the modified polyethersulfone membrane is safe and suitable for hemodialysis and bio-related applications.

Refinery gas contains abundant H₂ and a small amount of C₁–C₄ hydrocarbons. Here, we propose a condensability sieving strategy to realize preferential permeation of hydrocarbons over H₂ by developing halogen-induced porous coordination polymer (PCP) mixed matrix membranes (MMMs) that display condensability sieving gas transport. The 4-Cl-PCP, 5-Cl-PCP and 5-Br-PCP are synthesized by using Zr⁴⁺ and X-isophthalic acid (where X ​= ​4-Cl or 5-Cl or 5-Br) exhibit increased gas adsorption capacity with the increase in carbon number of the feed gas, but with almost no H₂ adsorption. MMMs containing the PCPs with different charge distributions enhance condensability sieving selectivity and inhibit diffusion selectivity. The permeances of the MMMs originated from condensability sieving are consistent with the polarizability-dependent adsorption of the PCP. The selectivity of the obtained MMMs for n-C₄H₁₀/H₂, C₃H₈/H₂, C₂H₆/H₂, and CH₄/H₂ achieve ∼40, ∼15, ∼5, and ∼2, respectively, exhibiting promising applications in refinery gas purification owing to their lower energy consumption compared with H₂-preferential permeation membranes.

In response to global efforts to combat climate change, many research efforts have contributed to upgrading cryogenic distillation, an energy-intensive petrochemical operation, especially for olefin/paraffin separation. Metal-organic framework (MOF) membranes can be a competitive candidate for this purpose. In this work, we reviewed the main progress of MOF membranes for olefin/paraffin separations, with the main focus on the potential of ZIF-8 for C₃H₆/C₃H₈ separation. Membranes of other potential materials, including covalent organic framework (COF) for olefin/paraffin separation, were also reviewed in detail. We then projected our views on searching for next-generation materials for high-performance olefin/paraffin separations. Finally, a guide of future research perspectives was provided to enable the first membrane of olefin/paraffin separation to be commercialized.

The selective transport of water/ions through conventional forward osmosis (FO) membranes is largely impeded by solution-diffusion and internal concentration polarization (ICP). Herein, we report a novel air nanobubbles (ANBs) incorporated sandwich-structured carbon nanotube membrane (CNM) for highly permeable and stable FO desalination by taking advantage of the nanofluidic transport at the solid/liquid/vapor interface. Fluorinated multi-walled carbon nanotubes (F-MWCNTs) were assembled as the superhydrophobic interlayer between a hydrophilic cellulose acetate (CA) layer and a hydrophilic polyacrylonitrile (PAN) nanofibrous layer. The trapped ANBs in the superhydrophobic F-MWCNT layer crucially regulated the continuous water flow and effectively prevented salt diffusion. When tested with DI water as feed solution (FS) and 1 ​M NaCl as draw solution (DS), the ANBs incorporated sandwich-structured CNM achieved high water flux (158.0 ​L ​m⁻² ​h⁻¹) and ultralow reverse salt flux (0.4 ​g ​m⁻² ​h⁻¹) simultaneously, far beyond the state-of-the-art FO membranes. The PAN nanofibrous layer well protected the entrapped ANBs to allow a more durable FO performance. An ANBs-regulated nanofluidic flow model was proposed to elucidate selective water/salt transport mechanism. This work revealed the feasibility of ANBs incorporated membranes for osmosis-driven processes.

Covalent Organic Frameworks (COFs) have attracted significant interest as promising separation membrane materials for their well-organized porous system and highly ordered crystalline structure. However, compared with the molecular and ionic separation in liquid phase, the advance of the COF membrane in gas separation has been relatively slow. To achieve desirable gas separation performance, the pore size of the COF membrane is expected to be regulated into the gas molecule-selective region, and also the tuning of pore enviroment is of importance. This review focuses on the key progress of the pore regulation strategies for the COF membrane towards gas separation. We highlight the different design concepts for selective gas transport channels, and introduce the specific applications to elucidate the structure-performance relationship of the COF membrane. We discuss the critical challenges and opportunities faced by the COF membranes in the field of gas separation, aiming at guiding the direction of the future efforts and promoting their development.