Membrane Material Research Articles

Application of Fabric Phase Sorptive Extraction as a Green Method for the Analysis of 10 Anti-Diabetic Drugs in Environmental Water Samples

Due to the increased prevalence of diabetes, the consumption of anti-diabetic drugs for its treatment has likewise increased. Metformin is an anti-diabetic drug that is commonly prescribed for patients with type 2 diabetes and has been frequently detected in surface water and wastewaters, thus representing an emerging contaminant. Metformin can be prescribed in combination with other classes of anti-diabetic drugs; however, these drugs are not sufficiently investigated in environmental samples. Fabric phase sorptive extraction (FPSE) has emerged as a simple and green method for the extraction of analytes in environmental samples. In this study, FPSE coupled with a high-performance liquid chromatography diode array detector (HPLC-DAD) was employed for the simultaneous analysis of different classes of anti-diabetic drugs (metformin, dapagliflozin, liraglutide, pioglitazone, gliclazide, glimepiride, glargine, repaglinide, sitagliptin, and vildagliptin) in environmental water samples. Four different fabric membranes were synthesized but the microfiber glass filter coated with sol-gel polyethylene glycol (PEG 300) was observed to be the best FPSE membrane. The parameters affecting the FPSE process were optimized using a combination of one-factor-at-a-time processes and the design of experiments. The FPSE was evaluated as a green extraction method, based on green sample preparation criteria. The FPSE-HPLC-DAD method achieved acceptable validation results and was applied for the simultaneous analysis of anti-diabetic drugs in surface and wastewater samples. Glimepiride was detected below the quantification limit in both lake and river water samples. Dapagliflozin, liraglutide, and glimepiride were detected at 69.0 ± 1.0 μg·L−1, 71.9 ± 0.4 μg·L−1, and 93.9 ± 1.3 μg·L−1, respectively, in the city wastewater influent. Dapagliflozin and glimepiride were still detected below the quantification limit in city wastewater effluent. For the hospital wastewater influent, metformin and glimepiride were detected at 1158 ± 21 μg·L−1 and 28 ± 0.8 μg·L−1, respectively, while only metformin (392.6 ± 7.7 μg·L−1) was detected in hospital wastewater effluent.

Improvement of Sound-Absorbing Wool Material by Laminating Permeable Nonwoven Fabric Sheet and Nonpermeable Membrane

Thin sound-absorbing materials are particularly desired in space-constrained applications, such as in the automotive industry. In this study, we theoretically analyzed the structure of relatively thin glass wool or polyester wool laminated with a nonpermeable polyethylene membrane and a permeable nonwoven fabric sheet. We also measured and compared the sound-absorption coefficients of these samples between experimental and theoretical values. The sound-absorption coefficient was derived using the transfer matrix method. The Rayleigh model was applied to describe the acoustic behavior of glass wool and nonwoven sheet, while the Miki model was used for polyester wool. Mathematical formulas were employed to model an air layer without damping and a vibrating membrane. These acoustic components were integrated into a transfer matrix framework to calculate the sound-absorption coefficient. The sound-absorption coefficients of glass wool and polyester wool were progressively enhanced by sequentially adding suitable nonwoven fabric and PE membranes. A sample approximately 10 mm thick, featuring permeable and nonpermeable membranes as outer layers of porous sound-absorbing material, achieved a sound-absorption coefficient equivalent to that of a sample occupying 20 mm thickness (10 mm of porous sound-absorbing material with a 10 mm back air layer).

Smart next-gen drying solution: A study of design, development and performance evaluation of IoT-enabled IR-assisted refractance window dryer

Refractance window drying is a technique that has great potential to dry commodities, with better quality at an affordable cost. However, there is still a lack of awareness regarding its use and implementation in academic curricula as well as in industry. This study aims to design and develop a low-cost and effective Internet of Things (IoT) enabled Infrared (IR) assisted refractance window dryer. The effect of different flexible materials used as membranes with the same thickness was also investigated. Then, experiments were conducted on papaya pulp to study the performance of the developed dryer. The drying time (reduced moisture content up to 4%) was observed for the papaya pulp sample by employing Low-density polyethylene (LDPE), Polypropylene (PP), Polytetrafluoroethylene (PTFE), White Polyethylene Terephthalate (W-PET) and Transparent polyethylene terephthalate (T-PET) material as a membrane were 300, 330, 360, 330, and 300 min respectively. After thoroughly testing membrane materials properties, it is concluded that the T-PET membrane has superior thermal, mechanical, and optical properties. After an exhaustive examination of the marketplace scrutiny, the payback period was found to be 0.55 years.

MONOCRYSTALLINE DIAMOND MEMBRANES WITH A THICKNESS OF 10 MICRONS, MANUFACTURED BY PLASMA ETCHING

New applications of high-quality synthetic diamond in sensors and integrated photonic circuits, which are being rapidly developed nowdays, often demand freestanding diamond membranes with a thickness of about 10 microns as a substrate. However, the process of thin single-crystal diamond membranes fabrication, as well as their subsequent processing are challenging due to the high hardness, chemical resistance and brittleness of the material. Our work demonstrates a method for creating freestanding diamond membranes mounted on a thick diamond substrate using reactive ion etching of single-crystalline diamond wafers in plasma with mechanical protective masks. The optimal thickness of a diamond wafer for membranes etching is determined in the range from 100 to 120 µm with mandatory plane-parallel polishing of the sides. We experimentally studied the interaction of RF discharge SF6 based plasma with diamond surface during deep etching with mechanical protective masks of various shapes. It was found that the use of thick masks leads to an uneven rate of diamond etching over the entire area of the formed membrane. We have assessed ion sputtering resistance of various mask materials in SF6 based plasma, and found the most promising mask materials for deep diamond etching (steel, copper, diamond). We have fabricated diamond membranes with a thickness of 11,5 µm (and more), mounted on a durable 60 µm (and more) thick frames, and studied their characteristics. After etching membrane surface roughness was less than 25 nm, and the unevenness of their thickness did not exceed 20%. Also, we compare different methods for controlling the depth of diamond etching and the thickness of the resulting membranes, including mechanical measurements, IR spectral reflectometry, optical profilometry and electron microscopy. For citation: Golovanov A.V., Yun M.I., Bondarenko M.G., Prosin A.A., Tarelkin S.A. Monocrystalline diamond membranes with a thickness of 10 microns, manufactured by plasma etching. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 10. P. 55-64. DOI: 10.6060/ivkkt.20246710.1y.

Techno-Economic Analysis of a Carbon Molecular Sieve-Based Xylene Isomer Purification Process.

The separation and purification of xylene isomers is critical to the production of polyethylene terephthalate (PET). These separations are complex to operate and demand tremendous amounts of energy and thus are an opportunity for reducing industrial energy consumption. Membranes provide a low-energy footprint technology with simpler operation, and recently, membrane materials have been developed that are capable of separating xylene isomers. While these materials have demonstrated the ability to separate xylenes, they have yet to be commercially deployed. This work conducts a techno-economic analysis (TEA) to provide insight on the commercial attractiveness of a p-xylene selective carbon molecular sieve (CMS) membrane from both a cost and energy standpoint. This TEA was conducted through the pairing of a Maxwell-Stefan transport framework for rigid microporous materials with process modeling. Single-stage organic solvent reverse osmosis (OSRO) and pervaporation processes were used to evaluate the effects of recovery, selectivity, and diffusivity on the energy intensity and cost of the xylene separation. The final analysis used two systems, a single pervaporation stage followed by two OSRO stages, which was compared against a three-stage OSRO cascade. These were benchmarked against the commercial Parex process. We estimate that the membrane processes have the potential to enable impressive cost savings compared to the Parex process. While both systems outperformed the Parex process in terms of cost, the pervaporation/OSRO hybrid process was able to achieve the lowest cost of all due to its reduced membrane surface area compared to standalone OSRO. These findings demonstrate the potential of membrane systems in the field of difficult small molecule solvent separations.

Preparation and properties of bio-based PA56/SiO2–NH2 composite nanofiber membranes for high efficiency oil-water separation

With the continuous development of environmental protection and resource recycling demands, the development of bio-based separation membrane materials has increasingly attracted attention. Bio-based polyamide 56 (PA56), exhibiting excellent hydrophilicity, spinnability, and mechanical properties, is expected to complement and replace traditional separation membrane materials. In this study, the electrospinning preparation and structural control of PA56 nanofiber membranes were achieved through the optimization of PA56 content and mixed solvent ratios. The study found that when the PA56 content was 16 wt% and the formic acid to acetone ratio in the mixed solvent was 8:2, the nanofiber diameter distribution was the most uniform. Building on this, amino-functionalized modified silica (SiO2–NH2) nanoparticles were introduced to prepare PA56/SiO2–NH2 composite nanofiber membranes featuring a cobweb-like nanofiber network and micro-nodule structure. The effects of the addition of SiO2–NH2 nanoparticles on the morphology, structure, and properties of the fiber membranes were studied. The results indicate that the control of the mixed solvent ratio and the addition of SiO2–NH2 nanoparticles led to the formation of a cobweb-like nanofiber network and micro-nano nodular structure on the nanofiber surface, enhancing the hydrophilicity of PA56 nanofiber membranes. The M − 3 membrane with a nanoparticle addition amount of 0.8 wt% exhibited high hydrophilicity and underwater superoleophobic properties, achieving efficient separation of stable oil-in-water emulsions with a separation efficiency of 99.8 %. This work provides a new bio-based membrane material and its preparation method for treating oily wastewater using the membrane separation method.

Fabrication of ultrafiltration membrane with antibacterial properties by blending Ag/UiO-66-NH2 and bamboo cellulose

Cellulose is a widely available organic substance that forms membranes with excellent hydrophilicity and biocompatibility. However, it is prone to biological contamination because its surface is conducive towards the accumulation of biologically active substances, which has hindered its application potential. In this work, an antimicrobial cellulose-based membrane (Ag/UiO-66-NH2@BCM) with high water flux, high retention rate, and good hydrophilicity was prepared. At an optimal blend ratio of 1 wt% Ag/UiO-66-NH2, the membrane exhibited significant improvements, including a 31% increase in pure water flux, a Bovine Serum Albumin retention rate of 99.6%, and a water flux recovery of 97.4%. Crucially, the membrane demonstrated potent antibacterial, showcasing its broad-spectrum antimicrobial properties. Investigations into the ability of Ag/UiO-66-NH2@BCM to remove Pb2+, Cd2+, and Cr6+ ions from a water column revealed that the maximum adsorption capacity of the monolayer was 405, 390, and 328 mg/g, respectively. The composite membrane demonstrated broad-spectrum and highly effective antimicrobial properties, along with efficient removal of heavy metal ions. The proposed method can be utilized to prepare other composite membranes for water treatment and other fields of membrane separation technology.

Computational Analysis of Permeance Prediction for Gas Separation Membrane Using Countercurrent Flow Model

Gas separation polymeric membranes have gained significant attention in various industries, including gas processing, petrochemicals, and environmental applications. Accurately predicting the permeance of these membranes is crucial for optimizing their design and performance. This paper presented a numerical prediction model for the permeance of a binary gas mixture under various process conditions, using only algebraic equations to minimize the calculation effort. The model considers input parameters such as feed and permeate flow rates, feed pressure, feed and permeate mole fraction, and membrane area. It demonstrates the behavior of permeance and selectivity in this study. The study also presented two case studies that utilize predicted selectivity to model counter-current flow and compare the results with experimental data from the literature. The first case study involves recovering helium from natural gas using an asymmetric high-flux membrane. The second case study separates air using nano-porous carbon as the membrane material. The numerical analysis successfully accurately predicted the permeance of gas separation polymeric membranes. The model accounted for variations in membrane thickness, feed composition, and operating conditions, providing valuable insights into the overall performance of the membrane system. It also allowed for the optimization of membrane design and operational parameters to enhance separation efficiency and productivity. The study showcased the effectiveness of numerical techniques in accurately predicting membrane performance. The developed model can be a valuable tool for membrane designers and engineers, enabling them to optimize the design and operation of gas separation systems.

Biomimetic mineralization of collagen from fish scale to construct a functionally gradient lamellar bone-like structure for guided bone regeneration

Wide used guided bone regeneration (GBR) membrane materials, such as collagen, Teflon, and other synthesized polymers, present a great challenge in term of integrating the mechanical property and degradation rate when addressing critical bone defects. Therefore, inspired by the distinctive architecture of fish scales, this study utilized epigallocatechin gallate to modify decellularized fish scales following biomimetic mineralization to fabricate a GBR membrane that mimics the structure of lamellar bone. The structure, physical and chemical properties, and biological functions of the novel GBR membrane were evaluated. Results indicate that the decellularized fish scale with 5 remineralization cycles (5R-E-DCFS) exhibited a composite and structure similar to natural bone and had a special functionally gradient mineral contents character, demonstrating excellent mechanical properties, hydrophilicity, and degradation properties. In vitro, the 5R-E-DCFS membrane exhibited excellent cytocompatibility promoting Sprague-Dawley (SD) rat bone marrow mesenchymal stem cell proliferation and differentiation up-regulating the expression of osteogenic-related genes and proteins. Furthermore, in vivo, the 5R-E-DCFS membrane promoted the critical skull bone defects of SD rats repairment and regeneration. Therefore, this innovative biomimetic membrane holds substantial clinical potential as an ideal GBR membrane with mechanical properties for space-making and suitable degradation rate for bone regeneration to manage bone defects.

Effects of electrode/electrolyte materials on heavy-metal removal in industrial wastewater with flow capacitive deionization method

The expansion of industrial facilities poses a significant environmental risk due to the generation of extensive wastewater containing complex components that effluent human health. Flow-electrode Capacitive Deionization (FCDI) technology has emerged as a promising solution for wastewater treatment due to its unlimited adsorption capacity and continuous long-term operations compared to conventional systems. This study investigates the efficiency of the FCDI system in purifying industrial wastewater by extracting complex heavy metal ions, intending to achieve complete recycling and zero discharge. Different electrolyte/electrode materials were investigated to achieve high removal efficiency, including electrolytes such as sodium chloride (NaCl) and sodium sulfate (Na2SO4), and electrodes such as active carbon (AC) and C65 carbon black (C65 CB) used in lithium-ion batteries. We found that the innovative combination of Na2SO4 electrolyte with 0.1 g of C65 CB exhibited an exceptional salt removal efficiency of 90 %, surpassing NaCl electrolyte which showed 68 % efficiency. Additionally, we observed higher adsorption with C65 CB slurry compared to AC when using Na2SO4 electrolyte. To deepen our insights, Molecular Dynamics (MD) simulations were conducted to explore heavy metal ions interactions with electrode/electrolyte and membrane materials under an electric field. The results indicated that Ni2+ ions had the highest passage rate of 80 % across the membrane, followed by Cr2+, Cu2+, and Zn2+. Furthermore, superior adsorption of Ni2+ ions onto the C65 CB electrode was noted, contributing to enhanced charge transfer and overall conductivity. Furthermore, we evaluated the economic and environmental implications associated with implementing the FCDI system in practical. This study presents a novel approach by using C65 carbon black (CB) with Na2SO4 as the electrolyte, indicating high adsorption efficiency at low carbon loading electrode. This combination offers a cost-effective and sustainable solution for improving complex heavy metal ion removal in FCDI systems. Overall, our study’s findings significantly contribute to offering crucial insights into optimizing FCDI technology for efficient heavy metal ions removal in industrial wastewater treatment using lithium-ion battery anode/cathode electrode material.

Supramolecular Interfacial Assembly: Integrating Supramolecular Hosts into Polymeric Membranes through an Aqueous Interface

Efficient incorporation of supramolecular hosts in polymeric membranes can impart the overall matrix with new properties for a range of cutting‐edge applications. Here, we introduce a Supramolecular Interfacial Assembly (SIA) method for the fabrication of polymeric membranes featuring embedded macrocycles. Through harnessing the quasi‐liquid nature of the concentrated polymer solution, SIA orchestrates the homogenous spreading of macrocycles in an aqueous layer on its surface, leading to the creation of an interface between “water/water” phases, subsequently forming a cross‐linked membrane driven by supramolecular electrostatic interactions. Remarkably, compared to the traditional interfacial polymerization, SIA adheres to a “green” paradigm without the need for organic solvents. The resultant composite membrane exhibits superior performance in organic solvent nanofiltration (OSN), owing to the precise molecular sieving property provided by the macrocycles with well‐defined permanent cavities. This fabrication method holds great promise for the innovative design of composite membranes, which can greatly impact the production of smart membrane materials for advanced technology applications in the future.

Supramolecular Interfacial Assembly: Integrating Supramolecular Hosts into Polymeric Membranes through an Aqueous Interface.

Efficient incorporation of supramolecular hosts in polymeric membranes can impart the overall matrix with new properties for a range of cutting-edge applications. Here, we introduce a Supramolecular Interfacial Assembly (SIA) method for the fabrication of polymeric membranes featuring embedded macrocycles. Through harnessing the quasi-liquid nature of the concentrated polymer solution, SIA orchestrates the homogenous spreading of macrocycles in an aqueous layer on its surface, leading to the creation of an interface between "water/water" phases, subsequently forming a cross-linked membrane driven by supramolecular electrostatic interactions. Remarkably, compared to the traditional interfacial polymerization, SIA adheres to a "green" paradigm without the need for organic solvents. The resultant composite membrane exhibits superior performance in organic solvent nanofiltration (OSN), owing to the precise molecular sieving property provided by the macrocycles with well-defined permanent cavities. This fabrication method holds great promise for the innovative design of composite membranes, which can greatly impact the production of smart membrane materials for advanced technology applications in the future.

Study on photocatalytic degradation and antibacterial properties of conjugated microporous polymers/TiO2 composite membranes

Conjugated microporous polymers (CMPs) are widely used in the field of photocatalysis due to their unique conjugated structures and various synthesis methods. Herein, we report the design and synthesis of conjugated microporous polymers hollow spheres (CMPs-HS) superhydrophilic modified by acetylcysteine (CMPs-HS-S) and compounded with the inorganic semiconductor material titanium dioxide (CMPs-HS-S/TiO2) for efficient photocatalytic degradation. To facilitate recycling, the composite membrane material was prepared by combining the materials mentioned above with PVDF membrane. The composite membrane materials had good hydrophilic and photocatalytic properties. Under visible light, the degradation rate of tetracycline (TC) (10 mg/L 180 min) reached 90 %, and the bactericidal rates for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 89 % and 99.99 %, respectively. The efficient photocatalytic performance of the composite membranes could be attributed to the hollow sphere structure of CMPs and the role of TiO2 as a photogenic electron transfer platform. Additionally, the hydrophilicity of the membrane also helped to accelerate the occurrence of photocatalytic reactions. After electron paramagnetic resonance (EPR) detection, h+, 1O2 and O2− were proved to be important reactive substances, which played a major role in degradation. These studies reflect the versatility of CMPs-based photocatalysts and provide a new idea for the future development of CMPs-based photocatalysts.

Nacre-inspired graphene oxide/polyethyleneimine-based ultra-thin heterogeneous superwetting membrane for highly stable separation of oil-in-water emulsions

Since the massive discharge of oily wastewater seriously affects both humans and natural development, the performance of conventional membrane materials in terms of interfacial stability and antifouling in the treatment of surfactant-containing emulsified oily wastewater is a major challenge. In this work, a novel nacre-inspired graphene oxide/polyethyleneimine-based ultra-thin chemically heterogeneous superwetting membrane was fabricated through vacuum-assisted self-assembly and post-modification methods for oil-in-water emulsion separation. The nacre-inspired heterogeneous membrane exhibited superhydrophilicity, underwater superoleophobicity (underwater oil contact angle was 157.7°), excellent crude oil adhesion resistance, high acid/alkaline stability, outstanding salt resistance, and good mechanical properties (Young’s modulus 1391.7 MPa). The heterogeneous membranes showed separation efficiencies of more than 99.9 % for a range of oil-in-water emulsions. The high-value membranes could achieve the permeances of 917–1256 L m−2h−1 bar−1 for pure water and 339.7–577 L m−2h−1 bar−1 for emulsion through a dead-end filter device, with the optimal long-term stable permeance only decreasing by 30.0 % compared to the initial value. After six test cycles, the membrane’s antifouling and self-cleaning properties were enhanced by constructing heterogeneous superwetting properties, and the flux recovery rate remained at 96.5 %. All of these results indicated that this method provides new ideas for the design and fabrication of highly stable and antifouling membrane materials.

Constructing multi-path channels in graphene oxide-based membrane for high-efficiency oil/water separation

Graphene oxide (GO) membranes have demonstrated significant potential for effective wastewater treatment; however, their tortuous and irregular water transport pathways through stacked nanosheets pose considerable challenges. In this study, we present a novel approach for fabricating faveolate-structured graphene oxide nanomesh (GONM) membranes, enhanced by the in situ growth of Co(OH)2 nanosheets to facilitate oil–water separation. The incorporation of in-plane pathways through the porous GONM, alongside the enlargement of interlayer pathways from Co(OH)2 growth, significantly improves water permeance. The nanopores present in the holey GONM reduce diffusion pathways, while intercalation of Co(OH)2 nanosheets increases channel sizes and stabilizes the GONM structure. By manipulating the mass ratio between GONM and cobalt salt, we optimized the membrane, achieving an exceptional water permeance of 224.2 L m-2h−1 bar−1, surpassing GO membranes. Additionally, the resultant membranes exhibit remarkable underwater anti-oil adhesion performance and efficient separation capabilities for a wide variety of oil-in-water emulsions, with separation efficiencies exceeding 99.1 %. This work provides valuable insights into the intentional manipulation of surface topography and hierarchical nanochannels in membrane materials, paving the way for high-efficiency water treatment solutions.

Fabrication and characterization of low-cost ceramic membranes from coal fly ash and natural sand

Coal fly ash, an industrial solid waste product, and natural sand, a commonly available and inexpensive natural material, were used to fabricate ceramic membranes that are both affordable and sustainable. These ceramic membranes were fabricated by the uniaxial compaction technique using a manual hydraulic pressing machine. The effects of various fabrication parameters such as the sintering temperature and the amount of natural sand utilized, on the properties of the resulting ceramic membranes were extensively evaluated. X-ray fluorescence (XRF) analysis of the starting materials confirmed the presence of SiO2 and Al2O3, two key inorganic materials required for the fabrication of ceramic membranes. Heavy metals present in the raw coal fly ash were leached out prior to the fabrication process. The coal fly ash and natural sand were mixed in different proportions and the fabricated ceramic membranes were characterized using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), and Thermogravimetric analysis (TGA). The properties of the optimized membranes were further studied to ascertain their mechanical strength, chemical stability, porosity, water absorption, water permeability, and shrinkage behaviour. The membrane fabricated with 20 wt% sand content and at 1000 °C sintering temperature had pore size of 0.64 µm and 34.7 % porosity, exhibited good mechanical strength (7.71 MPa), and exceptional chemical stability. The membrane also showed a remarkable water permeability of 32.23 L/m2/h. This study showed that natural sand and coal fly ash can be efficiently employed to develop a multifunctional filtration membrane with adjustable properties that can be utilized in water purification.

Fabrication of flexible multifunctional graphene-based composite membrane with improved hydrophobicity and thermal conductivity characters for thermal management

The lifetime of electronic devices in complex environments is affected by the impact of high temperature water vapor on their performance. Equipping electronic devices with superhydrophobic properties and improved thermal conductivity will be the strategy of the future. In this paper, a surface material with high thermal conductivity and superhydrophobic properties is explored to address the problem of electronic device failure caused by heat and water vapor. To solve this problem, anti-temperature superhydrophobicity can be obtained by spraying alumina/nano-silicon carbide/thermoplastic elastomer composite powder (Al2O3/nano-SiC/SEBS) modified with 1 H,1 H,2 H,2H-perfluorooctyltriethoxysilane (POTS) on graphene membranes. A spherical Al2O3/nano-SiC composite superhydrophobic coating (ASS-GM) was formed on the surface of graphene-based composite membranes by spraying method. The results showed that the optimal ratio was m(Al2O3): m(SiC) = 8:1, and the static water contact angle of the coating was 162 ± 2.5°, and the surface energy was reduced. The ASS-GM significantly improves the thermal conductivity and superhydrophobicity of graphene-based composite membranes, achieving a double improvement in performance. The coating also offers excellent self-cleaning and antifouling properties compared to other materials. The ASS-GM is able to maintain a certain hydrophobicity angle (156 ± 1.5°) in harsh environments. This work provides practical applications for electronic coatings, which are important for improving the overall reliability and durability of electronic products.

Hydrogen Separation Membranes: A Material Perspective

The global energy market is shifting toward renewable, sustainable, and low-carbon hydrogen energy due to global environmental issues, such as rising carbon dioxide emissions, climate change, and global warming. Currently, a majority of hydrogen demands are achieved by steam methane reforming and other conventional processes, which, again, are very carbon-intensive methods, and the hydrogen produced by them needs to be purified prior to their application. Hence, researchers are continuously endeavoring to develop sustainable and efficient methods for hydrogen generation and purification. Membrane-based gas-separation technologies were proven to be more efficient than conventional technologies. This review explores the transition from conventional separation techniques, such as pressure swing adsorption and cryogenic distillation, to advanced membrane-based technologies with high selectivity and efficiency for hydrogen purification. Major emphasis is placed on various membrane materials and their corresponding membrane performance. First, we discuss various metal membranes, including dense, alloyed, and amorphous metal membranes, which exhibit high hydrogen solubility and selectivity. Further, various inorganic membranes, such as zeolites, silica, and CMSMs, are also discussed. Major emphasis is placed on the development of polymeric materials and membranes for the selective separation of hydrogen from CH4, CO2, and N2. In addition, cutting-edge mixed-matrix membranes are also delineated, which involve the incorporation of inorganic fillers to improve performance. This review provides a comprehensive overview of advancements in gas-separation membranes and membrane materials in terms of hydrogen selectivity, permeability, and durability in practical applications. By analyzing various conventional and advanced technologies, this review provides a comprehensive material perspective on hydrogen separation membranes, thereby endorsing hydrogen energy for a sustainable future.

Multi-hierarchical structured PTFE membrane for liquid desiccant dewatering via membrane distillation

Poly (tetrafluoroethylene) (PTFE) can be used for robust separation membranes owing to its exceptional chemical and thermal stabilities. Simultaneously achieving construction of hierarchical pore structures and re-entrant surface microstructures during the fabrication of PTFE membrane holds significant importance in addressing the issues of low flux and membrane wetting in membrane distillation (MD). Herein, we proposed a flexible method for manufacturing hierarchically structured PTFE membrane by combining electrospinning/spraying with sintering/welding. The present approach facilitated the controlled fabrication of a superhydrophobic PTFE membrane with slippery surface (exhibiting a water contact angle of 153.5°, and an ultralow sliding angle of 7.5°) without using fluoride-based solvents or external nanoparticles. Moreover, the anti-wetting mechanism and performance stability of the PTFE membranes in MD were thoroughly investigated. In liquid desiccant regeneration experiments, the 20 wt% LiCl solution was successfully concentrated to 28.64 wt%. Furthermore, the PTFE membrane demonstrated a stable flux (>30 kg m−2 h−1) and relatively low permeate conductivity (<15 μs cm−1) during treating simulated seawater for 30 h. The present work offers a new approach to fabricate multi-hierarchical structured superhydrophobic membranes for desalination and regeneration of liquid desiccants.

TFE Terpolymers: Once Promising - Are There Still Perspectives in the 21st Century? Part II: Processing, Properties, Applications.

Tetrafluoroethylene (TFE) terpolymers have emerged as advantageous substitutes for polytetrafluoroethylene (PTFE). Therefore, they are being considered as alternatives to PTFE in many application areas. The advantages of TFE terpolymers include their facile processability at elevated temperatures, their solubility in some polar organic solvents, their inertness against aqueous acids, aqueous bases and a large number of mostly nonpolar organic solvents, their low dielectric constant, their low refractive index as well as useful electro- and thermochemical properties. This review on TFE terpolymers focuses on their processing including shaping and surface modification as well as on selected properties including wettability, dielectric properties, mechanical response behavior, chemical stability, and degradability. Applications including their use as elastomeric sealing material, liner and cladding layer as well as their use as material for membranes, microfluidic devices, photonics, photovoltaics, energy storage, energy harvesting, sensors, and nanothermitic composites will be discussed. The review concludes with a discussion of the future potential of TFE terpolymers and scientific challenges to be addressed by future research on TFE terpolymers.