Gas Separation Membranes Research Articles

Polyvinyl Alcohol/Zr-based Metal Organic Framework Mixed-matrix Membranes Synthesis and Application for Hydrogen Separation

Membrane gas separation is an environmentally friendly and economical method used to separate valuable gases, industrial process gas wastes, and carbon dioxide from mixed gases. The most important part of this method is the membranes. Gas separation membranes are expected to have high separation and permeability performance, high mechanical strength, easy and fast production capability, and low prices. Polymer-based membranes are mostly preferred depending on the ease of modification capability. In this study, a zirconium-based metal organic framework (Zr-MOF, MIL-140 A) was synthesized and used as a filler within polyvinyl alcohol (PVA) matrix for the selective separation of hydrogen (H2) from carbon dioxide (CO2). The effect of MIL-140 A addition on the mechanical, structural, and morphological properties of PVA was evaluated. The MIL-140 A significantly improved the mechanical strength of the membrane. According to the gas separation results, the increasing concentration of MIL-140 A increased the selective separation performance of the nanocomposite membrane. The highest mechanical strength (43.1 MPa) and best film-forming ability were obtained with 3 wt% MIL-140 A loaded membrane. The ideal H2/CO2 selectivity and hydrogen permeability were obtained as 5.6 and 944 Barrer, respectively at 2 bar feed pressure and room temperature. The highest ideal H2/CO2 selectivity was obtained as 6.3 with the H2 permeability of 959 Barrer when the MIL-140 A ratio was 4 wt%.

Advanced and sustainable manufacturing methods of polymer-based membranes for gas separation: a review

The fabrication of membranes for gas separation presents challenges that hinder their deployment as a truly sustainable technology. This review systematically explores the evolution and advancements in materials and manufacturing methods of polymer-based membranes, with a keen emphasis on sustainability and efficiency. The review delineates a broad spectrum of manufacturing techniques, ranging from traditional methods to cutting-edge approaches such as layer-by-layer assembly, and green synthesis, highlighting their implications for environmental sustainability, performance enhancement, scalability, and economic viability. Key findings indicate a significant shift towards greener solvents, bio-based polymers and processes that reduce waste and costs. Critical analysis uncovers a growing focus on understanding the life cycle of membranes and developing strategies for end-of-life such as recycling and the use of biodegradable materials, underscoring the commitment of the community to minimizing environmental footprints.

Molecular design of free volume structure in thermally rearranged polybenzoxazole membranes for gas separation studied by positron annihilation

AbstractIn this work, 2,2‐bis(3‐amino‐4‐hydroxyphenyl) hexafluoropropane (APAF) was used as the fixed diamine monomer, and 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA), 3,3′,4,4′‐biphenyltetracarboxylic diandhydride (BPDA) and pyromellitic dianhydride (PMDA) were selected as four different dianhydride monomers, respectively, to prepare the thermally rearranged polybenzoxazole (TR‐PBO) gas separation membranes with different structures via a thermal rearrangement reaction at 450°C. The microstructure of TR‐PBO membranes was investigated using X‐ray diffraction and positron annihilation spectroscopy. All the TR‐PBO membranes exhibit bimodal free volume structure, containing ultramicropores (<0.7 nm) and micropores (<2 nm) with size of 3.6–4.6 and 7.6–8.4 Å, respectively. As the steric hindrance of the bridging groups in the dianhydride monomers increases, the radius and number of pores in the membranes increases, leading to an increase in fractional free volume (FFV). The pure gas permeation test shows a positive correlation between gas permeability and FFV in the TR‐PBO membranes, indicating that an increase in FFV is favorable for the diffusion of gas molecules. Particularly, the ultramicropores play a decisive role on the gas selectivity. All the TR‐PBO membranes exhibit excellent gas permeaselectivity. Among them, the H2/CH4 separation performance of APAF‐6FDA and APAF‐ODPA membranes approaches the 2008 Robeson upper bound, which is due to the high number of both micropores and ultramicropores. Our results demonstrate that the free volume structure of polymer membranes can be designed by selecting monomers with different structures and utilizing thermal rearrangement reactions, allowing for the preparation of gas separation membranes with high permeability and selectivity.

Pore-filled composite membranes for water vapor separation: Bench-scale advancements and semi-empirical modeling

Efficient scale-up processes of gas separation membranes require a thorough assessment of performance across various parameters. Semi-empirical modeling based on theory and empirical data is an attractive approach to predict the required performance. Despite numerous studies on the performance of gas separation membranes depending on internal parameters such as morphology and geometry, relatively few studies on performance dependent on external parameters have been reported. In this study, we propose semi-empirical modeling for the performance of membranes as a function of external parameters using a bench-scale pore-filled composite membranes for water vapor separation. As external parameters, we selected temperature, pressure, relative humidity (RH), and feed flow rate. These parameters influence water vapor permeance, water flux, and RH reduction, which are theoretical indicators of the performance of water vapor separation membranes. A power regression analysis was used to find the power of individual parameters (Y = Coefficient (k) ∙ Xpower), and a multiple linear regression analysis (finite power law model, Y = k ∙ X1α ∙ X2β…) was used to develop a semi-empirical model with the correlations of these parameters. The modeling values closely coincided with measured values, suggesting the effectiveness of the proposed modeling. This method is expected to simplify the prediction of membrane performance, offering valuable insights for potential scale-up processes.

Synergistic effect of combining UiO-66 nanoparticles and MXene nanosheets in Pebax mixed-matrix membranes for CO2 capture

The use of membrane-based gas separation has garnered significant interest owing to its cost-effectiveness, outstanding performance and positive environmental impact. The performance of gas separation membranes can be considerably enhanced by mixed-matrix membranes (MMMs), but poor interactions between additives and membrane matrix and the agglomeration of highly incorporated fillers in MMMs limit the benefits of overcoming tradeoff effect. Therefore, the regulation of the state of fillers in membrane matrix is a crucial indicator in the development of MMMs. In this study, MXene (Ti3C2Tx) nanosheets and UiO-66 nanoparticles were prepared and used as fillers, in combination with a Pepax-1657 matrix, to synthesize MMMs for CO2-gas separation. As-prepared MMMs were used for the separation; the large pores (0.5–0.6 nm) of UiO-66 served as a highway to enhance CO2 permeability, and MXene nanosheets were used as selective channels to achieve high selectivity via the terminal polar surface groups of MXene. The combination of UiO-66 and MXene not only enhanced the selectivity, but also increased the solubility and diffusivity via selective CO2 adsorption and the tortuous pathway provided by MXene nanosheets. As a result, adding MXene and UiO-66 to Pebax helped MMMs overcome the tradeoff effect. MMMs loaded with 10 wt% MXene/UiO-66 exhibited a CO2 permeability coefficient of 214.6 Barrer and an ideal CO2/N2 selectivity coefficient of 102. Dual filler-containing MMMs showed enhanced CO2 permeability coefficient and CO2/N2 selectivity in comparison to pristine Pebax and individual nanofiller-added membranes. In this study, the combination of 2D MXene and UiO-66 nanoparticles exerted a synergistic effect in improving the CO2 separation efficiency of MMMs. This research provides a novel route for fabricating high-performance MMMs in the separation of CO2.

Enhanced interaction of CO2 with TCNQ-modified CuO nanoparticle-infused PEO matrix: A novel approach in gas transport technology

We developed a composite membrane based on polyethylene oxide (PEO), achieving high CO2 selectivity, by incorporating 7,7,8,8-tetracyanoquinodimethane (TCNQ)-modified CuO nanoparticles into the PEO matrix. The addition of TCNQ helps in evenly distributing the CuO nanoparticles throughout the membrane, preventing them from clumping together. This treatment not only enhances the dispersion of CuO particles but also imparts a positive charge to their surface, which is beneficial for increasing the selectivity for CO2 over N2. The extent of this surface charge modification on the CuO nanoparticles was evaluated using X-ray photoelectron spectroscopy (XPS), while the synergy between the polymer and the additives was verified through Fourier-transform infrared (FT-IR) spectroscopy studies. The combination of CuO nanoparticles in the membrane contributes to both barrier and carrier effects, enhancing the gas selectivity. This is further aided by the intrinsic properties of PEO, a rubber-like polymer known for its good gas permeance. As a result of these combined effects, the PEO/CuO/TCNQ membrane exhibited a remarkable CO2 selectivity of 393 and a CO2 permeance of 3.9 gas permeation unit (GPU). The superior separation performance of this membrane can be ascribed to three main factors: enhanced solubility due to the oxide layer on the particle surfaces and in the polymer matrix, improved transport efficiency via reversible interactions thanks to the positively charged surface, and the effective barrier provided by the nanoparticles against N2 transport. These findings are expected to contribute significantly to future studies on the surface modification of metal nanoparticles and in the field of gas separation membranes.

Interfacially initiated polymerization of epoxides: A thin-film synthesis platform for XLPEO gas separation membranes

Crosslinked poly (ethylene oxide) (XLPEO) membranes are leading candidates for membrane post-combustion carbon capture, because of their high CO2/N2 selectivity and CO2 permeability. However, their crosslinked nature makes it difficult to process them into thin films through conventional coating techniques. In this study, interfacially initiated chain growth polymerization of epoxides is used to circumvent the XLPEO processing challenge whilst allowing in-situ crosslinking. The interfacial design strategy yields intrinsically crosslinked, epoxide-based PEO (eXLPEO) thin-film composite gas separation (GS) membranes consisting fully of CO2-philic ether bonds. An eXLPEO selective layer made from poly (ethylene glycol) diglycidyl ether was successfully deposited on a PAN support and, after introduction of densification steps and a PDMS sealing, gas selective membranes were obtained. Synthesis-structure-performance analysis revealed that multiple reaction condition combinations result in highly selective membranes with a tunable chemical structure. The best performing membranes showed CO2/N2 separation factors of 58 at 35 °C, with a stable operation at pressures from 2 to 10 bar, and retaining a separation factor of 30 at 65 °C. However, all membranes had a low CO2 permeance (<10 GPU), probably due to pore impregnation of the support layer. This work demonstrates for the first time the viability of interfacial polymerization for the synthesis of thin film eXLPEO GS membranes.

A Short Review of Advances in MOF Glass Membranes for Gas Adsorption and Separation.

The phenomenon of melting in metal-organic frameworks (MOFs) has recently garnered attention. Crystalline MOF materials can be transformed into an amorphous glassy state through melt-quenching treatment. The resulting MOF glass structure eliminates grain boundaries and retains short-range order while exhibiting long-range disorder. Based on these properties, it emerges as a promising candidate for high-performance separation membranes. MOF glass membranes exhibit permanent and accessible porosity, allowing for selective adsorption of different gas species. This review summarizes the melting mechanism of MOFs and explores the impact of ligands and metal ions on glassy MOFs. Additionally, it presents an analysis of the diverse classes of MOF glass composites, outlining their structures and properties, which are conducive to gas adsorption and separation. The absence of inter-crystalline defects in the structures, coupled with their distinctive mechanical properties, renders them highly promising for industrial gas separation applications. Furthermore, this review provides a summary of recent research on MOF glass composite membranes for gas adsorption and separation. It also addresses the challenges associated with membrane production and suggests future research directions.

Intrinsically Microporous Polyimides Derived from 2,2'-Dibromo-4,4',5,5'-bipohenyltetracarboxylic Dianhydride for Gas Separation Membranes.

This work aims to expand the structure-property relationships of bromo-containing polyimides and the influence of bromine atoms on the gas separation properties of such materials. A series of intrinsically microporous polyimides were synthesized from 2,2'-dibromo-4,4',5,5'-bipohenyltetracarboxylic dianhydride (Br-BPDA) and five bulky diamines, (7,7'-(mesitylmethylene)bis(8-methyldibenzo[b,e][1,4]dioxin-2-amine) (MMBMA), 7,7'-(Mesitylmethylene)bis(1,8-dimethyldibenzo[b,e][1,4] dioxin-2-amine) (MMBDA), 4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-diamine (TBDA1), 4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-3,9-diamine (TBDA2), and (9R,10R)-9,10-dihydro-9,10-[1,2]benzenoanthracene-2,6-diamine (DAT). The Br-BPDA-derived polyimides exhibited excellent solubility, high thermal stability, and good mechanical properties, with their tensile strength and modulus being 59.2-109.3 MPa and 1.8-2.2 GPa, respectively. The fractional free volumes (FFVs) and surface areas (SBET) of the Br-BPDA-derived polyimides were in the range of 0.169-0.216 and 211-342 m2 g-1, following the order of MMBDA > MMBMA > TBDA2 > DAT > TBDA1, wherein the Br-BPDA-MMBDA exhibited the highest SBET and FFV and thus highest CO2 permeability of 724.5 Barrer. Moreover, Br-BPDA-DAT displayed the best gas separation performance, with CO2, H2, O2, N2, and CH4 permeabilities of 349.8, 384.4, 69.8, 16.3, and 19.7 Barrer, and H2/N2 selectivity of 21.4. This can be ascribed to the ultra-micropores (<0.7 nm) caused by the high rigidity of Br-BPDA-DAT. In addition, all the bromo-containing polymers of intrinsic microporosity membranes exhibited excellent resistance to physical ageing.

Combining Interpretable Machine Learning and Molecular Simulation to Advance the Discovery of COF-Based Membranes for Acid Gas Separation

Combining Interpretable Machine Learning and Molecular Simulation to Advance the Discovery of COF-Based Membranes for Acid Gas Separation

Polynorbornenes with carbocyclic substituents: A perspective approach to highly permeable gas separation membranes

Gas transport properties of two sets of polynorbornenes bearing carbocyclic substituents of different nature (cyclohexyl, norbornyl, phenyl groups, and framed oligocyclic moieties) were systematically studied. The influence of side chain carbocyclic substituents on gas permeability and separation selectivity for CO2-containing gas pairs and gaseous hydrocarbons was evaluated. It was found that the presence of carbocyclic moieties in side chains of polynorbornenes promotes the increase in gas permeability similarly to that of SiMe3 groups, with this effect being enhanced by the increase in the number of cycles in the substituents. As a result, P(CO2) of the metathesis polymer with pentacene-based substituents is equal to 1200 Barrer. Studied polynorbornenes with carbocyclic substituents displayed promising gas separation selectivities: CO2/N2 separation selectivity up to 41 (above the 2008 upper bound in the Robeson diagram) and solubility-controlled hydrocarbon separation selectivity up to 16 for the n-butane/methane gas pair. For the polymer with pentacene-based substituents, the separation of the mixture of hydrocarbons and aging were studied. The studies revealed that the mixed gas C4/C1 separation selectivity of this polymer reaches 4, and a two-time reduction of permeability occurs in 8.5 months. Therefore, the incorporation of carbocyclic groups in the side chains of polynorbornenes can be considered as an efficient strategy for the design of polymeric gas separation membrane materials.

Rarefied gas flow in functionalized microchannels

The interaction of rarefied gases with functionalized surfaces is of great importance in technical applications such as gas separation membranes and catalysis. To investigate the influence of functionalization and rarefaction on gas flow rate in a defined geometry, pressure-driven gas flow experiments with helium and carbon dioxide through plain and alkyl-functionalized microchannels are performed. The experiments cover Knudsen numbers from 0.01 to 200 and therefore the slip flow regime up to free molecular flow. To minimize the experimental uncertainty which is prevalent in micro flow experiments, a methodology is developed to make optimal use of the measurement data. The results are compared to an analysis-based hydraulic closure model (ACM) predicting rarefied gas flow in straight channels and to numerical solutions of the linearized S-model and BGK kinetic equations. The experimental data shows that if there is a difference between plain and functionalized channels, it is likely obscured by experimental uncertainty. This stands in contrast to previous measurements in smaller geometries and demonstrates that the surface-to-volume ratio of 0.4 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}m-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document} seems to be too small for the functionalization to have a strong influence and highlights the importance of geometric scale for surface effects. These results also shed light on the molecular reflection characteristics described by the TMAC.

Advancement of membrane separation technology for organic pollutant removal.

In the face of growing global freshwater scarcity, the imperative to recycle and reuse water becomes increasingly apparent across industrial, agricultural, and domestic sectors. Eliminating a range of organic pollutants in wastewater, from pesticides to industrial byproducts, presents a formidable challenge. Among the potential solutions, membrane technologies emerge as promising contenders for treating diverse organic contaminants from industrial, agricultural, and household origins. This paper explores cutting-edge membrane-based approaches, including reverse osmosis, nanofiltration, ultrafiltration, microfiltration, gas separation membranes, and pervaporation. Each technology's efficacy in removing distinct organic pollutants while producing purified water is scrutinized. This review delves into membrane fouling, discussing its influencing factors and preventative strategies. It sheds light on the merits, limitations, and prospects of these various membrane techniques, contributing to the advancement of wastewater treatment. It advocates for future research in membrane technology with a focus on fouling control and the development of energy-efficient devices. Interdisciplinary collaboration among researchers, engineers, policymakers, and industry players is vital for shaping water purification innovation. Ongoing research and collaboration position us to fulfill the promise of accessible, clean water for all.

Graphene in gas separation membranes—State-of-the-art and potential spoors

Graphene and derivatives have been frequently used to form advanced nanocomposites. A very significant utilization of polymer/graphene nanocomposite was found in the membrane sector. The up-to-date overview essentially highpoints the design, features, and advanced functions of graphene nanocomposite membranes towards gas separations. In this concern, pristine thin layer graphene as well as graphene nanocomposites with poly(dimethyl siloxane), polysulfone, poly(methyl methacrylate), polyimide, and other matrices have been perceived as gas separation membranes. In these membranes, the graphene dispersion and interaction with polymers through applying the appropriate processing techniques have led to optimum porosity, pore sizes, and pore distribution, i.e., suitable for selective separation of gaseous molecules. Consequently, the graphene derived nanocomposites brought about numerous revolutions in high performance gas separation membranes. The structural diversity of polymer/graphene nanocomposites has facilitated the membrane selective separation, permeation, and barrier processes especially in the separation of desired gaseous molecules, ions, and contaminants. Future research on the innovative nanoporous graphene-based membrane can overcome design/performance related challenging factors for technical utilizations.

Nanoporous Ti3C2O2 monolayer towards high permeance and selectivity for CO2/N2 separation: CO2-MXene interaction tuning

MXene, as a new gas separation membrane, has good stability and suitable pore topological structures to mitigate the greenhouse effect caused by excessive CO2 emission. However, the large quadrupole and polarizability of CO2 make it a strong interaction with MXene, thus leading to a strong solubility and weak diffusivity of CO2. Here, we design nanoporous Ti3C2O2 monolayers (YmXn) with exposed C atoms that could tune CO2-Ti3C2O2 interaction so as to improve gas separation performance by density functional theory and molecular dynamics simulation. The scope of “Cut-off” size is obtained by analyzing the gas separation state from un-permeation to permeation. Results reveal that nanoporous Ti3C2O2 membranes achieve both outstanding CO2 selectivity and permeance. The best-performance Y3X3-Ti possesses CO2 permeance of 1.01 × 10-4 and 2.56 × 10-5 mol s−1 m−2 Pa−1 for equimolar gas mixtures and flue gases, respectively, and both the CO2/N2 selectivity reach 100 %. The gas separation mechanism is dominated by diffusion selectivity rather than solution selectivity in nanoporous Ti3C2O2. The dynamic processes of gas permeation, including the center of mass, mean square displacement, and radial distribution function of the gases, are precisely investigated. The electrostatic repulsion between the C atoms in the channel of the membrane and CO2 follows the sequence Y3X3-C > Y2X4 > Y3X3-Ti, which is the key to regulating gas diffusion. Results of this work highlight that tuning gas-membrane interaction and designing “Cut-off” size are effective strategies to achieve excellent CO2 separation performance, and shed new light on the intrinsic mechanism in high-performance gas separation membranes.

Pressure-resistant and portable array gas membrane device for rapid Escherichia coli detection in infant milk powder via smartphone colorimetry with all-in-one preparation strategy

This study presents a novel Pressure-Resistant and Portable Array Gas Membrane Separation (PAGMS) device for the rapid, smartphone-based detection of Escherichia coli (E. coli) in infant milk powder. The PAGMS device efficiently separates acetic acid, a byproduct of E. coli growth, enhancing detection sensitivity. Utilizing bromocresol violet as an indicator, this method quantifies E. coli based on colorimetric changes, with UV spectrum absorbance shifts indicating a linear correlation (R2 = 0.9864) within 5.0–120 μmol/L acetic acid concentration. Visual MINTEQ simulations validate the mechanism behind the indicator’s response. The approach surpasses traditional plate culture methods in terms of sample preparation time, achieving detection within a comparable timeframe of 15 min, and can concurrently process up to 48 samples, thereby substantially enhancing analytical throughput while detecting E. coli with a limit of detection of 5 cfu/g. This method demonstrates enhanced sensitivity, speed, and high-throughput capabilities, offering significant advantages in food safety monitoring.

Naphthalene Tetrazole-Based Nickel Metal-Organic Framework as a Filler of Polycarbonate Membranes to Improve CO2 and H2 Separation.

A tetrazole-naphthalene linker was used to prepare a nickel MOF (metal-organic framework) (NiNDTz) with interesting properties: a specific surface area SBET of 320 m2g-1 (SLangmuir 436 m2g-1), high thermal stability (Tdonset = 300 °C), and CO2 uptake of 1.85 mmolg-1, attributed to the tetrazole groups to be used as fillers in gas separation membranes. The role of these groups was crucial in the mechanical properties of mixed membranes prepared using polycarbonate as a polymer matrix, providing a very homogeneous filler distribution and also in the gas separation properties since a simultaneous increase in permeability and selectivity was achieved, especially in the hybrid membrane containing 20% filler (PC@NiNDTz-20%). This membrane exhibited an excellent balance between permeability (P) and selectivity (α) with an increase in the permeability of CO2 and H2, 177 and 185%, respectively, and improvements in the selectivity of these gases against greenhouse gases such as methane and ethylene (between 15 and 28% improvement). These results make this membrane competitive to deal with separations in which these gases are involved, and are of special interest for the H2/CH4 separation since it clearly improves the performance of pure PC and no better PC-based membranes have been reported in the literature for this separation.

Tuning the assembly of MgNiO2 nanoparticles-infused polysulfone membranes for efficient gas separation: The selectivity-permeability conundrum

The persistent surge in global energy demand, coupled with escalating environmental apprehensions, has underscored the imperative for adept and sustainable gas separation technologies. Mixed matrix membranes (MMMs) have surfaced as a promising avenue to confront these multifaceted challenges, synergistically harnessing the strengths of conventional polymeric membranes and nanoparticle reinforcements. In this work, MMMs have been tailored for gas separation applications by incorporating MgNiO2 nanoparticles as an additive into the polysulfone (PSf) matrix as they provide additional space (in the form of nanoscale voids) for gas diffusion, facilitating faster gas transport, promoting selective permeation of specific gases, and enhancing membrane stability, in addition to their versatility, ease of preparation, cost-effectiveness and high activity. The crystalline nature of MgNiO2 nanoparticles, as characterized by finely tuned grain sizes, has been validated by powder X-ray diffraction (XRD) analysis. Gas permeation experiments on the developed MMMs encompassing a diverse range of pure gases and gas mixtures have been performed. Among the different MMMs investigated, PSM1 with a composition of 100 mg MgNiO2 nanoparticles has yielded substantial enhancements in permeability and selectivity. The PSM1 membrane exhibits remarkable permeance of 56.9 for H2, 16.3 for CH4, and 15 GPU for CO2, having ideal selectivity ratios of 3.5 and 3.8 for H2/CH4 and H2/CO2, respectively. Finally, this work provides new directions for improving the trade of relationship between the selectivity and permeability of gas mixtures under relevant process conditions.

Application of Graphene-Based Derived Rice Husk Waste for Membrane Gas Separation Technologies: A Comprehensive Review

This study intends to comprehensively evaluate the application of graphene-based nanofillers obtained from rice husk waste in the field of membrane gas separation technologies. Graphene, owing to its distinctive structural characteristics, has emerged as a highly promising filler material for membrane fabrication in gas separation applications. This comprehensive review provides an in-depth evaluation of the diverse synthesis methods employed and the resulting properties of graphene obtained from rice husk waste materials, with an inclusive chemical mechanism of graphene formation from rice husk waste. Furthermore, this study reveals the inherent capabilities of graphene in enhancing the performance of membranes while also examining the influence of nanofillers on solubility selectivity. In conclusion, it is imperative to underline the need for additional research and development activities aimed at expanding the efficiency and scalability of the membrane fabrication process through the utilization of graphene nanofillers derived from rice husk waste.

Construction and analysis of a detailed new database for gas separation membranes

The countless possibilities associated with the design of new materials for the Membrane Gas Separation Process highlight the need for the creation of databases, that are great tools to guide design choices. The scientific literature is poor in providing detailed information on gas separation membranes. This work aimed to present a heterogeneous and detailed database, which encompasses various types of membranes and permeating gases. In addition, its construction was presented in a transparent manner (ensuring its suitability and safe use) and an analysis of the mined attributes was performed. A database with 1672 records was built with more than 280 different membranes. In total, 29 attributes were collected from 42 different bibliographic references. A wide range of values was mined for most of the attributes. Permeation data for 11 gases were collected and five major types of membranes are present: polymer, zeolite, MMM, CMS, MOF, and ceramic. Most of the attributes had an insignificant linear correlation with gas permeability (including film thickness, pore size, temperature, and pressure), indicating a complex and contextually specific relationship. Total Pore Volume, Micropore Volume, and BET Area attributes were the morphological attributes that are most linearly correlated with gas permeability and can be good performance indicators for membranes, regardless of the material type. It is expected that the results presented will be useful to guide decision-making in the steps of designing new membranes for gas separation in a big picture context.