Fundamentals of Transport in Polymers and Membranes—Honorary Issue for Professor Giulio C. Sarti

A special issue of Membranes (ISSN 2077-0375). This special issue belongs to the section "Polymeric Membranes".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 31698

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1. Dipartimento di Ingegneria Civile Chimica Ambientale e dei Materiali, Alma Mater Studiorum Universita di Bologna, Via Terracini, 28-I-40131 Bologna, Italy
2. Institute for Materials and Processes, School of Engineering, University of Edinburgh, Sanderson Building, Robert Stevenson Road, Edinburgh EH9 3FB, UK
Interests: mass transport; thermodynamic models; diffusion; molecular simulation; equations of state; glassy polymers; mixed matrix membranes; gas separation, CO2 capture; thermodynamics; permeation
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Department of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum-University of Bologna, Via Terracini, 28, 40131 Bologna, Italy
Interests: glassy polymers; diffusion; membranes for gas separation; transport properties; thermodynamic modelling
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Special Issue Information

Dear colleagues,

We warmly invite you to submit your original work or review article to this Special Issue of Membranes in honor of Professor Sarti.

Dr. Sarti is an Emeritus Professor at the Alma Mater Studiorum, University of Bologna, after almost 40 years in the Department of Chemical Engineering. He started his career in the Chemical Engineering Department at the University “Federico II” in Naples, and, only ten years later, he had the opportunity to enter the Department of Chemical Engineering at his home university in Bologna, where he was appointed Full Professor in 1986. He served as Head of Department, directed the National Academic Society of Chemical Engineers (GRICU), and he participated on the Editorial Board of the journal Separation and Purification Methods from 1998 to 2003. Since 2008, he has been a member of the Academy of Science of Bologna Institute, founded in 1690.

He has co-authored more than 200 publications, which have been cited over 4800 times, with a H-index of 41.

During his career, Professor Sarti always aimed at solving practically relevant problems by invoking first principles of thermodynamics and thermomechanics of continuum. His efforts were devoted, in particular, to the analysis of rheological and transport properties of polymeric materials and its application to solve industrial problems such as polymer processing and membrane separations. He is one of the authors of the Non-Equilibrium Lattice Fluid (NELF) model and of the Standard Transport (ST) models for gas sorption and permeability in glassy polymers.

To acknowledge his contribution to the field of Membranes, this Special Issue will accept contributions from his friends, collaborators and estimators who would like to present novel or review works dealing with a fundamental analysis of selective materials with application in separation processes, such as membranes and adsorbents. The studies can include experimental and/or theoretical developments, aiming at a fundamental understanding of the process of fluid transport in solid materials and of its role in the separation.  
   
Applications of interest include but are not limited to: gas separation and CO2 capture, pervaporation, liquid permeation, water purification, organic solvent nanofiltration, bioseparations, membrane distillation, reverse osmosis, fuel cells, batteries, sensors, polymer desolventization, adsorption and polymer thermodynamics.

Topics of interest include the experimental analysis of fundamental aspects of sorption and transport in polymeric materials, such as glass transition, ageing, thin films, nanoconfinement, plasticization, swelling, competitive sorption, and stress effects. We will also welcome modeling works presenting macroscopic, atomistic, mesoscopic, or multiscale approaches that describe sorption and transport in solids.

We are looking forward to receiving your work for this Special Issue.

Prof. Dr. Maria Grazia De Angelis
Prof. Dr. Matteo Minelli
Guest Editors

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Published Papers (15 papers)

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17 pages, 6153 KiB  
Article
Effect of Packing Nonuniformity at the Fiber Bundle–Case Interface on Performance of Hollow Fiber Membrane Gas Separation Modules
by Lili Sun, Grigorios Panagakos and Glenn Lipscomb
Membranes 2022, 12(11), 1139; https://doi.org/10.3390/membranes12111139 - 13 Nov 2022
Cited by 3 | Viewed by 1355
Abstract
High-fidelity simulations of momentum and mass transfer within a hollow fiber gas separation membrane module are here reported. The simulations capture the potential detrimental effects of poor fiber packing at the bundle–case interface on fluid distribution and performance. Results are presented for both [...] Read more.
High-fidelity simulations of momentum and mass transfer within a hollow fiber gas separation membrane module are here reported. The simulations capture the potential detrimental effects of poor fiber packing at the bundle–case interface on fluid distribution and performance. Results are presented for both circular and planar fiber bundles. The length over which bundle–case gaps affects flow is determined. The length increases dramatically with increasing fiber packing fraction. As the packing fraction approaches 0.6, the impact extends over the entire bundle diameter for small modules (<1000 fibers). The results clearly demonstrate the detrimental effect of poor packing along the case and can be used to develop module manufacturing guidelines. To reduce computational costs, an equivalent planar bundle module approximation is developed. The approximate simulations agree well with results from full 3-D simulations and can reduce computational costs without sacrificing fidelity. Full article
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10 pages, 569 KiB  
Article
Toward Minimal Complexity Models of Membrane Reactors for Hydrogen Production
by Maria Anna Murmura, Stefano Cerbelli, Ludovica Manozzi and Maria Cristina Annesini
Membranes 2022, 12(11), 1115; https://doi.org/10.3390/membranes12111115 - 08 Nov 2022
Viewed by 1009
Abstract
Membrane reactors are inherently two-dimensional systems that require complex models for an accurate description of the different transport phenomena involved. However, when their performance is limited by mass transport within the reactor rather than by the selective product permeation across the membrane, the [...] Read more.
Membrane reactors are inherently two-dimensional systems that require complex models for an accurate description of the different transport phenomena involved. However, when their performance is limited by mass transport within the reactor rather than by the selective product permeation across the membrane, the 2D model may be significantly simplified. Here we extend results previously found for methane steam reforming membrane reactors to show that such simplified two-dimensional model admits either a straightforward analytical solution for the cross-section averaged concentration profile, or can be reduced to a 1D model with an enhanced Sherwood number, depending on the stoichiometry of the reaction considered. Interestingly, the stoichiometry does not affect the expression of the enhanced Sherwood number, indicating that a versatile tool has been developed for the determination of membrane reactor performance at an extremely low computational cost and good degree of accuracy. Full article
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16 pages, 3163 KiB  
Article
Effect of Polystyrene Synthesis Method on Water Sorption and Glass Transition
by Daniel T. Hallinan, Jr., Matteo Minelli, Onyekachi Oparaji, Andrea Sardano, Oluwagbenga Iyiola, Armando R. Garcia and Daniel J. Burnett
Membranes 2022, 12(11), 1059; https://doi.org/10.3390/membranes12111059 - 28 Oct 2022
Cited by 4 | Viewed by 1592
Abstract
Commodity PS is synthesized via free radical polymerization, whereas PS in block copolymers (BCPs) is typically synthesized via living anionic polymerization. The purpose of this work is to investigate how the synthesis method impacts important properties such as water sorption and glass transition [...] Read more.
Commodity PS is synthesized via free radical polymerization, whereas PS in block copolymers (BCPs) is typically synthesized via living anionic polymerization. The purpose of this work is to investigate how the synthesis method impacts important properties such as water sorption and glass transition temperature (Tg). Water sorption is important because the performance of nanostructured polymer membranes in various applications is known to be affected by environmental conditions such as humidity. Tg is important because it dictates processing conditions, both for commodity PS as well as BCPs such as thermoplastic elastomers. Water sorption in commercial PS was found to be 0.5 mgwater/gpolymer at the highest humidities investigated (about 80%), in agreement with literature. On the other hand, syndiotactic PS synthesized anionically at low temperature absorbed more water, up to 1.5 mgwater/gpolymer, due to higher free volume. The greatest impact on water sorption was due to addition of hydrophilic hydroxyl chain ends to atactic PS, which resulted in water sorption of up to 2.3 mgwater/gpolymer. In addition to measuring water sorption and dry Tg separately, the impact of relative humidity on PS Tg was examined. Combined differential scanning calorimetry and dynamic mechanical analysis show that on going from the dry state to high humidity, the Tg of PS decreases by 5 °C. Moreover, the tensile storage modulus of PS decreases from 1.58 GPa at 0% RH to 0.53 GPa at 40% RH. In addition to the practical relevance of this study, this report fills a gap in experimental literature by using a poor solvent system, PS/water, to examine plasticization in the pure polymer limit. Full article
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16 pages, 4016 KiB  
Article
Permeation of Ternary Mixture Containing H2S, CO2 and CH4 in Aquivion® Perfluorosulfonic Acid (PFSA) Ionomer Membranes
by Virginia Signorini, Marco Giacinti Baschetti, Diego Pizzi and Luca Merlo
Membranes 2022, 12(11), 1034; https://doi.org/10.3390/membranes12111034 - 24 Oct 2022
Cited by 2 | Viewed by 1340
Abstract
Aquivion® E87-12S Perfluorosulfonated acid ionomer material (PFSA) has been studied as a membrane technology for natural gas sweetening from CO2, H2S due to its interesting chemical and mechanical stability and good separation performance for polar compounds in humid [...] Read more.
Aquivion® E87-12S Perfluorosulfonated acid ionomer material (PFSA) has been studied as a membrane technology for natural gas sweetening from CO2, H2S due to its interesting chemical and mechanical stability and good separation performance for polar compounds in humid environments. In the present work, permeation of the H2S/CO2/CH4 ternary mixture in this short-side PFSA chain was investigated at pressures up to 10 bar, temperatures up to 50 °C, and in a range of relative humidity (RH) from 20% to 90%. The results obtained confirm the strong dependence of Aquivion® on water activity and temperature, and its ability to separate gases based on their water solubility without substantial differences between pure and mixed gas experiments. Indeed, even when tested in ternary mixture, the permeation behavior remains similar to that observed for pure components and binary mixtures. In particular, the permeability of H2S is higher than that of CO2 and methane CH4, reaching values of 500 Barrer at 50 °C and 80% RH, against 450 and 23 Barrer for the other two gases respectively. Additionally, when tested at higher pressures of up to 10 bar under humid conditions, the membrane properties remained largely unchanged, thus confirming the overall stability and durability of Aquivion® E87-12S in acid environments. Full article
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13 pages, 2072 KiB  
Article
The Rigid Adsorbent Lattice Fluid Model: Thermodynamic Consistency and Relationship to the Real Adsorbed Solution Theory
by Stefano Brandani
Membranes 2022, 12(10), 1009; https://doi.org/10.3390/membranes12101009 - 18 Oct 2022
Cited by 1 | Viewed by 1008
Abstract
The Rigid Adsorbent Lattice Fluid model has been shown to comply with all the requirements for thermodynamic consistency in the case of an adsorbent that does not undergo structural changes. This is achieved by introducing a correction to the reduced density function that [...] Read more.
The Rigid Adsorbent Lattice Fluid model has been shown to comply with all the requirements for thermodynamic consistency in the case of an adsorbent that does not undergo structural changes. This is achieved by introducing a correction to the reduced density function that multiplies the combinatorial term. A procedure to calculate the predicted adsorbed mixture activity coefficients has been presented that allows the production of excess Gibbs energy plots at a constant reduced grand potential. The predicted nonideality is structurally consistent with the Non-Ideal Adsorbed Solution Theory of Myers in terms of both its dependence on concentration and reduced grand potential. The ability to generate excess Gibbs energy values allows linking the new Rigid Adsorbent Lattice Fluid model to the traditional Real Adsorbed Solution Theory providing an alternative approach to predicting multicomponent adsorption based solely on pure component data. Full article
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17 pages, 3759 KiB  
Article
Purification of Adeno-Associated Virus (AAV) Serotype 2 from Spodoptera frugiperda (Sf9) Lysate by Chromatographic Nonwoven Membranes
by Jinxin Fan, Eduardo Barbieri, Shriarjun Shastry, Stefano Menegatti, Cristiana Boi and Ruben G. Carbonell
Membranes 2022, 12(10), 944; https://doi.org/10.3390/membranes12100944 - 27 Sep 2022
Cited by 5 | Viewed by 2625
Abstract
The success of adeno-associated virus (AAV)-based therapeutics in gene therapy poses the need for rapid and efficient processes that can support the growing clinical demand. Nonwoven membranes represent an ideal tool for the future of virus purification: owing to their small fiber diameters [...] Read more.
The success of adeno-associated virus (AAV)-based therapeutics in gene therapy poses the need for rapid and efficient processes that can support the growing clinical demand. Nonwoven membranes represent an ideal tool for the future of virus purification: owing to their small fiber diameters and high porosity, they can operate at high flowrates while allowing full access to target viral particles without diffusional limitations. This study describes the development of nonwoven ion-exchange membrane adsorbents for the purification of AAV2 from an Sf9 cell lysate. A strong anion-exchange (AEX) membrane was developed by UV grafting glycidyl methacrylate on a polybutylene terephthalate nonwoven followed by functionalization with triethylamine (TEA), resulting in a quaternary amine ligand (AEX-TEA membrane). When operated in bind-and-elute mode at a pH higher than the pI of the capsids, this membrane exhibited a high AAV2 binding capacity (9.6 × 1013 vp·mL−1) at the residence time of 1 min, and outperformed commercial cast membranes by isolating AAV2 from an Sf9 lysate with high productivity (2.4 × 1013 capsids·mL−1·min−1) and logarithmic reduction value of host cell proteins (HCP LRV ~ 1.8). An iminodiacetic acid cation-exchange nonwoven (CEX-IDA membrane) was also prepared and utilized at a pH lower than the pI of capsids to purify AAV2 in a bind-and-elute mode, affording high capsid recovery and impurity removal by eluting with a salt gradient. To further increase purity, the CEX-IDA and AEX-TEA membranes were utilized in series to purify the AAV2 from the Sf9 cell lysate. This membrane-based chromatography process also achieved excellent DNA clearance and a recovery of infectivity higher that that reported using ion-exchange resin chromatography. Full article
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11 pages, 4350 KiB  
Article
Thin Film Composite Membranes Based on the Polymer of Intrinsic Microporosity PIM-EA(Me2)-TB Blended with Matrimid®5218
by Mariagiulia Longo, Marcello Monteleone, Elisa Esposito, Alessio Fuoco, Elena Tocci, Maria-Chiara Ferrari, Bibiana Comesaña-Gándara, Richard Malpass-Evans, Neil B. McKeown and Johannes C. Jansen
Membranes 2022, 12(9), 881; https://doi.org/10.3390/membranes12090881 - 13 Sep 2022
Cited by 7 | Viewed by 2226
Abstract
In this work, thin film composite (TFC) membranes were fabricated with the selective layer based on a blend of polyimide Matrimid®5218 and polymer of intrinsic microporosity (PIM) composed of Tröger’s base, TB, and dimethylethanoanthracene units, PIM-EA(Me2)-TB. The TFCs were [...] Read more.
In this work, thin film composite (TFC) membranes were fabricated with the selective layer based on a blend of polyimide Matrimid®5218 and polymer of intrinsic microporosity (PIM) composed of Tröger’s base, TB, and dimethylethanoanthracene units, PIM-EA(Me2)-TB. The TFCs were prepared with different ratios of the two polymers and the effect of the PIM content in the blend of the gas transport properties was studied for pure He, H2, O2, N2, CH4, and CO2 using the well-known time lag method. The prepared TFC membranes were further characterized by IR spectroscopy and scanning electron microscopy (SEM). The role of the support properties for the TFC membrane preparation was analysed for four different commercial porous supports (Nanostone Water PV 350, Vladipor Fluoroplast 50, Synder PAN 30 kDa, and Sulzer PAN UF). The Sulzer PAN UF support with a relatively small pore size favoured the formation of a defect-free dense layer. All the TFC membranes supported on Sulzer PAN UF presented a synergistic enhancement in CO2 permeance, and CO2/CH4 and CO2/N2 ideal selectivity. The permeance increased about two orders of magnitude with respect to neat Matrimid, up to ca. 100 GPU, the ideal CO2/CH4 selectivity increased from approximately 10 to 14, and the CO2/N2 selectivity from approximately 20 to 26 compared to the thick dense reference membrane of PIM-EA(Me2)-TB. The TFC membranes exhibited lower CO2 permeances than expected on the basis of their thickness—most likely due to enhanced aging of thin films and to the low surface porosity of the support membrane, but a higher selectivity for the gas pairs CO2/N2, CO2/CH4, O2/N2, and H2/N2. Full article
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16 pages, 3752 KiB  
Article
Dry Glass Reference Perturbation Theory Predictions of the Temperature and Pressure Dependent Separations of Complex Liquid Mixtures Using SBAD-1 Glassy Polymer Membranes
by Bennett D. Marshall, Wenjun Li and Ryan P. Lively
Membranes 2022, 12(7), 705; https://doi.org/10.3390/membranes12070705 - 12 Jul 2022
Cited by 5 | Viewed by 1374
Abstract
In this work we apply dry glass reference perturbation theory (DGRPT) within the context of fully mutualized diffusion theory to predict the temperature and pressure dependent separations of complex liquid mixtures using SBAD-1 glassy polymer membranes. We demonstrate that the approach allows for [...] Read more.
In this work we apply dry glass reference perturbation theory (DGRPT) within the context of fully mutualized diffusion theory to predict the temperature and pressure dependent separations of complex liquid mixtures using SBAD-1 glassy polymer membranes. We demonstrate that the approach allows for the prediction of the membrane-based separation of complex liquid mixtures over a wide range of temperature and pressure, using only single-component vapor sorption isotherms measured at 25 °C to parameterize the model. The model was then applied to predict the membrane separation of a light shale crude using a structure oriented lumping (SOL) based compositional model of petroleum. It was shown that when DGRPT is applied based on SOL compositions, the combined model allows for the accurate prediction of separation performance based on the trend of both molecular weight and molecular class. Full article
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15 pages, 2044 KiB  
Article
Use of the Dispersion Coefficient as the Sole Structural Parameter to Model Membrane Chromatography
by Eleonora Lalli, Giulio C. Sarti and Cristiana Boi
Membranes 2022, 12(7), 668; https://doi.org/10.3390/membranes12070668 - 28 Jun 2022
Cited by 1 | Viewed by 1309
Abstract
The characterization and modelling of membrane chromatography processes require the axial dispersion coefficient as a relevant and effective intrinsic property of porous media, instead of arbitrary assumptions on pore size distribution. The dispersion coefficient can be easily measured by experiments completely independent of [...] Read more.
The characterization and modelling of membrane chromatography processes require the axial dispersion coefficient as a relevant and effective intrinsic property of porous media, instead of arbitrary assumptions on pore size distribution. The dispersion coefficient can be easily measured by experiments completely independent of chromatographic tests. The paper presents the prediction of experimentally obtained breakthrough curves using B14-TRZ-Epoxy2 membranes as a test case; the mathematical model implemented is based on the use of the experimentally measured axial dispersion coefficient as an input parameter. Application of the model and its comparison with the data demonstrate that alternative ways of explaining the shape of breakthrough curves, based on unverified assumptions about the membrane pore size distribution, are not feasible and not effectively supported by experimental evidence. In contrast, the axial dispersion coefficient is the only measurable parameter that accounts for all the different contributions to the dispersion phenomenon that occurs in the membrane chromatography process, including the effects due to porous structure and pore size distribution. Therefore, mathematical models that rely on the mere assumption of pore size distribution, regardless of the role of the axial dispersion coefficient, are in fact arbitrary and ultimately misleading. Full article
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13 pages, 1838 KiB  
Article
Chemical Vapour Deposition Graphene–PMMA Nanolaminates for Flexible Gas Barrier
by Antonio Baldanza, Maria Giovanna Pastore Carbone, Cosimo Brondi, Anastasios C. Manikas, Giuseppe Mensitieri, Christos Pavlou, Giuseppe Scherillo and Costas Galiotis
Membranes 2022, 12(6), 611; https://doi.org/10.3390/membranes12060611 - 12 Jun 2022
Cited by 3 | Viewed by 1882
Abstract
Successful ways of fully exploiting the excellent structural and multifunctional performance of graphene and related materials are of great scientific and technological interest. New opportunities are provided by the fabrication of a novel class of nanocomposites with a nanolaminate architecture. In this work, [...] Read more.
Successful ways of fully exploiting the excellent structural and multifunctional performance of graphene and related materials are of great scientific and technological interest. New opportunities are provided by the fabrication of a novel class of nanocomposites with a nanolaminate architecture. In this work, by using the iterative lift-off/float-on process combined with wet depositions, we incorporated cm-size graphene monolayers produced via Chemical Vapour Deposition into a poly (methyl methacrylate) (PMMA) matrix with a controlled, alternate-layered structure. The produced nanolaminate shows a significant improvement in mechanical properties, with enhanced stiffness, strength and toughness, with the addition of only 0.06 vol% of graphene. Furthermore, oxygen and carbon dioxide permeability measurements performed at different relative humidity levels, reveal that the addition of graphene leads to significant reduction of permeability, compared to neat PMMA. Overall, we demonstrate that the produced graphene–PMMA nanolaminate surpasses, in terms of gas barrier properties, the traditional discontinuous graphene–particle composites with a similar filler content. Moreover, we found that the gas permeability through the nanocomposites departs from a monotonic decrease as a function of relative humidity, which is instead evident in the case of the pure PMMA nanolaminate. This work suggests the possible use of Chemical Vapour Deposition graphene–polymer nanolaminates as a flexible gas barrier, thus enlarging the spectrum of applications for this novel material. Full article
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19 pages, 23935 KiB  
Article
Mixed Matrix Membranes Loaded with a Porous Organic Polymer Having Bipyridine Moieties
by Sandra Rico-Martínez, Cristina Álvarez, Antonio Hernández, Jesús A. Miguel and Ángel E. Lozano
Membranes 2022, 12(6), 547; https://doi.org/10.3390/membranes12060547 - 25 May 2022
Cited by 11 | Viewed by 2207
Abstract
Mixed matrix membranes (MMMs), derived from three aromatic polyimides (PIs), and an affordable porous organic polymer (POP) having basic bipyridine moieties were prepared. Matrimid and two fluorinated polyimides, which were derived from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride and 2,2′-bis(4-aminophenyl)hexafluoropropane (6F6F) or 2,4,6-trimethyl-m-phenylenediamine (6FTMPD), were employed as [...] Read more.
Mixed matrix membranes (MMMs), derived from three aromatic polyimides (PIs), and an affordable porous organic polymer (POP) having basic bipyridine moieties were prepared. Matrimid and two fluorinated polyimides, which were derived from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride and 2,2′-bis(4-aminophenyl)hexafluoropropane (6F6F) or 2,4,6-trimethyl-m-phenylenediamine (6FTMPD), were employed as polymer matrixes. The used POP was a highly microporous material (surface area of 805 m2 g−1) with excellent thermal and chemical stability. The MMMs showed good compatibility between the PIs and POP, high thermal stabilities and glass transition temperatures superior to those of the neat PI membranes, and good mechanical properties. The addition of POP to the matrix led to an increase in the gas diffusivity and, thus, in permeability, which was associated with an increase in the fractional free volume of MMMs. The increase in permeability was higher for the less permeable matrix. For example, at 30 wt.% of POP, the permeability to CO2 and CH4 of the MMMs increased by 4- and 7-fold for Matrimid and 3- and 4-fold for 6FTMPD. The highest CH4 permeability led to a decrease in CO2/CH4 selectivity. The CO2/N2 separation performance was interesting, as the selectivity remained practically constant. Finally, the POP showed no molecular sieving effect towards the C2H4/C2H6 and C3H6/C3H8 gas pairs, but the permeability increased by about 4-fold and the selectivity was close to that of the matrix. In addition, because the POP can form metal ion bipyridine complexes, modified POP-based MMMs could be employed for olefin/paraffin separations. Full article
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30 pages, 7266 KiB  
Article
Molecular Characterization of Membrane Gas Separation under Very High Temperatures and Pressure: Single- and Mixed-Gas CO2/CH4 and CO2/N2 Permselectivities in Hybrid Networks
by Sylvie Neyertz, David Brown, Saman Salimi, Farzaneh Radmanesh and Nieck E. Benes
Membranes 2022, 12(5), 526; https://doi.org/10.3390/membranes12050526 - 17 May 2022
Cited by 4 | Viewed by 2825
Abstract
This work illustrates the potential of using atomistic molecular dynamics (MD) and grand-canonical Monte Carlo (GCMC) simulations prior to experiments in order to pre-screen candidate membrane structures for gas separation, under harsh conditions of temperature and pressure. It compares at 300 °C and [...] Read more.
This work illustrates the potential of using atomistic molecular dynamics (MD) and grand-canonical Monte Carlo (GCMC) simulations prior to experiments in order to pre-screen candidate membrane structures for gas separation, under harsh conditions of temperature and pressure. It compares at 300 °C and 400 °C the CO2/CH4 and CO2/N2 sieving properties of a series of hybrid networks based on inorganic silsesquioxanes hyper-cross-linked with small organic PMDA or 6FDA imides. The inorganic precursors are the octa(aminopropyl)silsesquioxane (POSS), which degrades above 300 °C, and the octa(aminophenyl)silsesquioxane (OAPS), which has three possible meta, para or ortho isomers and is expected to resist well above 400 °C. As such, the polyPOSS-imide networks were tested at 300 °C only, while the polyOAPS-imide networks were tested at both 300 °C and 400 °C. The feed gas pressure was set to 60 bar in all the simulations. The morphologies and densities of the pure model networks at 300 °C and 400 °C are strongly dependent on their precursors, with the amount of significant free volume ranging from ~2% to ~20%. Since measurements at high temperatures and pressures are difficult to carry out in a laboratory, six isomer-specific polyOAPS-imides and two polyPOSS-imides were simulated in order to assess their N2, CH4 and CO2 permselectivities under such harsh conditions. The models were first analyzed under single-gas conditions, but to be closer to the real processes, the networks that maintained CO2/CH4 and CO2/N2 ideal permselectivities above 2 were also tested with binary-gas 90%/10% CH4/CO2 and N2/CO2 feeds. At very high temperatures, the single-gas solubility coefficients vary in the same order as their critical temperatures, but the differences between the penetrants are attenuated and the plasticizing effect of CO2 is strongly reduced. The single-gas diffusion coefficients correlate well with the amount of available free volume in the matrices. Some OAPS-based networks exhibit a nanoporous behavior, while the others are less permeable and show higher ideal permselectivities. Four of the networks were further tested under mixed-gas conditions. The solubility coefficient improved for CO2, while the diffusion selectivity remained similar for the CO2/CH4 pair and disappeared for the CO2/N2 pair. The real separation factor is, thus, mostly governed by the solubility. Two polyOAPS-imide networks, i.e., the polyorthoOAPS-PMDA and the polymetaOAPS-6FDA, seem to be able to maintain their CO2/CH4 and CO2/N2 sieving abilities above 2 at 400 °C. These are outstanding performances for polymer-based membranes, and consequently, it is important to be able to produce isomer-specific polyOAPS-imides for use as gas separation membranes under harsh conditions. Full article
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18 pages, 1868 KiB  
Article
Water Sorption in Glassy Polyvinylpyrrolidone-Based Polymers
by Dominik Borrmann, Andreas Danzer and Gabriele Sadowski
Membranes 2022, 12(4), 434; https://doi.org/10.3390/membranes12040434 - 17 Apr 2022
Cited by 12 | Viewed by 2800
Abstract
Polyvinylpyrrolidone (PVP)-based polymers are excellent stabilizers for food supplements and pharmaceutical ingredients. However, they are highly hygroscopic. This study measured and modeled the water-sorption isotherms and water-sorption kinetics in thin PVP and PVP-co-vinyl acetate (PVPVA) films. The water sorption was measured at 25 [...] Read more.
Polyvinylpyrrolidone (PVP)-based polymers are excellent stabilizers for food supplements and pharmaceutical ingredients. However, they are highly hygroscopic. This study measured and modeled the water-sorption isotherms and water-sorption kinetics in thin PVP and PVP-co-vinyl acetate (PVPVA) films. The water sorption was measured at 25 °C from 0 to 0.9 RH, which comprised glassy and rubbery states of the polymer-water system. The sorption behavior of glassy polymers differs from that in the rubbery state. The perturbed-chain statistical associating fluid theory (PC-SAFT) accurately describes the water-sorption isotherms for rubbery polymers, whereas it was combined with the non-equilibrium thermodynamics of glassy polymers (NET-GP) approach to describe the water-sorption in the glassy polymers. Combined NET-GP and PC-SAFT modeling showed excellent agreement with the experimental data. Furthermore, the transitions between the PC-SAFT modeling with and without NET-GP were in reasonable agreement with the glass transition of the polymer-water systems. Furthermore, we obtained Fickian water diffusion coefficients in PVP and in PVPVA from the measured water-sorption kinetics over a broad range of humidities. Maxwell-Stefan and Fickian water diffusion coefficients yielded a non-monotonous water concentration dependency that could be described using the free-volume theory combined with PC-SAFT and NET-GP for calculating the free volume. Full article
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13 pages, 2423 KiB  
Article
Moving beyond 90% Carbon Capture by Highly Selective Membrane Processes
by Yang Han and W. S. Winston Ho
Membranes 2022, 12(4), 399; https://doi.org/10.3390/membranes12040399 - 01 Apr 2022
Cited by 5 | Viewed by 2544
Abstract
A membrane-based system with a retentate recycle process in tandem with an enriching cascade was studied for >90% carbon capture from coal flue gas. A highly CO2-selective facilitated transport membrane (FTM) was utilized particularly to enhance the CO2 separation efficiency [...] Read more.
A membrane-based system with a retentate recycle process in tandem with an enriching cascade was studied for >90% carbon capture from coal flue gas. A highly CO2-selective facilitated transport membrane (FTM) was utilized particularly to enhance the CO2 separation efficiency from the CO2-lean gases for a high capture degree. A techno-economic analysis showed that the retentate recycle process was advantageous for ≤90% capture owing to the reduced parasitic energy consumption and membrane area. At >90% capture, the enriching cascade outperformed the retentate recycle process since a higher feed-to-permeate pressure ratio could be applied. An overall 99% capture degree could be achieved by combining the two processes, which yielded a low capture cost of USD47.2/tonne, whereas that would be USD 42.0/tonne for 90% capture. This FTM-based approach for deep carbon capture and storage can direct air capture for the mitigation of carbon emissions in the energy sector. Full article
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Review

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71 pages, 22439 KiB  
Review
Modelling Sorption and Transport of Gases in Polymeric Membranes across Different Scales: A Review
by Eleonora Ricci, Matteo Minelli and Maria Grazia De Angelis
Membranes 2022, 12(9), 857; https://doi.org/10.3390/membranes12090857 - 31 Aug 2022
Cited by 14 | Viewed by 4182
Abstract
Professor Giulio C. Sarti has provided outstanding contributions to the modelling of fluid sorption and transport in polymeric materials, with a special eye on industrial applications such as membrane separation, due to his Chemical Engineering background. He was the co-creator of innovative theories [...] Read more.
Professor Giulio C. Sarti has provided outstanding contributions to the modelling of fluid sorption and transport in polymeric materials, with a special eye on industrial applications such as membrane separation, due to his Chemical Engineering background. He was the co-creator of innovative theories such as the Non-Equilibrium Theory for Glassy Polymers (NET-GP), a flexible tool to estimate the solubility of pure and mixed fluids in a wide range of polymers, and of the Standard Transport Model (STM) for estimating membrane permeability and selectivity. In this review, inspired by his rigorous and original approach to representing membrane fundamentals, we provide an overview of the most significant and up-to-date modeling tools available to estimate the main properties governing polymeric membranes in fluid separation, namely solubility and diffusivity. The paper is not meant to be comprehensive, but it focuses on those contributions that are most relevant or that show the potential to be relevant in the future. We do not restrict our view to the field of macroscopic modelling, which was the main playground of professor Sarti, but also devote our attention to Molecular and Multiscale Hierarchical Modeling. This work proposes a critical evaluation of the different approaches considered, along with their limitations and potentiality. Full article
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