Membranes

17 pages, 5813 KiB

Open AccessArticle

Hybrid Version of the Kedem–Katchalsky–Peusner Equations for Diffusive and Electrical Transport Processes in Membrane

by Andrzej Ślęzak and Sławomir M. Grzegorczyn

Membranes 2025, 15(1), 36; https://doi.org/10.3390/membranes15010036 - 20 Jan 2025

Viewed by 614

One of the most important formalisms used to describe membrane transport is Onsager–Peusner thermodynamics (TOP). Within the TOP framework, a procedure has been developed for the transformation of the Kedem–Katchalsky (K–K) equations for the transport of binary electrolytic solutions across a membrane into [...] Read more.

One of the most important formalisms used to describe membrane transport is Onsager–Peusner thermodynamics (TOP). Within the TOP framework, a procedure has been developed for the transformation of the Kedem–Katchalsky (K–K) equations for the transport of binary electrolytic solutions across a membrane into the Kedem–Katchalsky–Peusner (K–K–P) equations. The membrane system with an Ultra Flo 145 Dialyser membrane used for hemodialysis and aqueous NaCl solutions was used as experimental setup. The H version of K–K–P formalism for binary electrolyte solutions was used to evaluate theoretical coefficients characterizing fluxes of energies and efficiencies for membrane transport processes. The coupling coefficients of membrane processes and the dissipative energy flux were calculated on the basis of the Peusner coefficients obtained from transformation of K–K coefficients. The knowledge of dissipative energy flux, which is a function of thermodynamic forces, allows for the determination of the energy conversions during transport processes in a membrane system. In addition, a frictional interpretation of the obtained coefficients is presented. Full article

(This article belongs to the Section Membrane Fabrication and Characterization)

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15 pages, 2566 KiB

Open AccessArticle

Evaluation of Ceramic Membrane Filtration for Alternatives to Microplastics in Cosmetic Formulations Using FlowCam Analysis

by Seung Yeon Kim, Soyoun Kim and Chanhyuk Park

Membranes 2025, 15(1), 35; https://doi.org/10.3390/membranes15010035 - 19 Jan 2025

Viewed by 578

Abstract

The rapid expansion of the cosmetics industry has significantly increased the adoption of alternative microplastics in response to increasingly stringent global environmental regulations. This study presents a comparative analysis of the treatment performance of silica powder and cornstarch—common alternatives for microplastics in cosmetics—using [...] Read more.

The rapid expansion of the cosmetics industry has significantly increased the adoption of alternative microplastics in response to increasingly stringent global environmental regulations. This study presents a comparative analysis of the treatment performance of silica powder and cornstarch—common alternatives for microplastics in cosmetics—using ceramic membrane filtration combined with flow imaging microscopy (FlowCam) to analyze particle behavior. Bench-scale crossflow filtration experiments were performed with commercially available alumina ceramic membranes. By analyzing high-resolution images from FlowCam, the transport and retention behaviors of the two microplastic alternatives were examined by comparing their morphological properties. Despite their similar particle sizes, the cornstarch demonstrated a higher removal efficiency (82%) than the silica (72%) in the ceramic membrane filtration due to its greater tendency to aggregate. This increased tendency for aggregation suggests that cornstarch may contribute to faster fouling, while the stability and uniformity of silica particles result in less fouling. The FlowCam analysis revealed that the cornstarch particles experienced a slight increase in circularity and compactness over time, likely due to physical swelling and aggregation, while the silica particles retained their shape and structural integrity. These findings highlight the impact of the morphological properties of alternative microplastics on their filtration behavior and fouling potential. Full article

(This article belongs to the Special Issue Ceramic Membranes for Removal of Emerging Pollutants)

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14 pages, 1251 KiB

Open AccessArticle

Enhancing Virus Filter Performance Through Pretreatment by Membrane Adsorbers

by Solomon Isu, Shu-Ting Chen, Raheleh Daneshpour, Hironobu Shirataki, Daniel Strauss, Andrew L. Zydney, Xianghong Qian and Sumith Ranil Wickramasinghe

Membranes 2025, 15(1), 34; https://doi.org/10.3390/membranes15010034 - 17 Jan 2025

Viewed by 1029

Abstract

Virus filtration is used to ensure the high level of virus clearance required in the manufacture of biopharmaceutical products such as monoclonal antibodies. Flux decline during virus filtration can occur due to the formation of reversible aggregates consisting of self-assembled monomeric monoclonal antibody [...] Read more.

Virus filtration is used to ensure the high level of virus clearance required in the manufacture of biopharmaceutical products such as monoclonal antibodies. Flux decline during virus filtration can occur due to the formation of reversible aggregates consisting of self-assembled monomeric monoclonal antibody molecules, particularly at high antibody concentrations. While size exclusion chromatography is generally unable to detect these reversible aggregates, dynamic light scattering may be used to determine their presence. Flux decline during virus filtration may be minimized by pretreating the feed using a membrane adsorber in order to disrupt the reversible aggregates that are present. The formation of reversible aggregates is highly dependent on the monoclonal antibody and the feed conditions. For the pH values investigated here, pretreatment of the feed using a hydrophobic interaction membrane adsorber was the most effective in minimizing flux decline during virus filtration. Ion exchange membranes may also be effective if the monoclonal antibody and membrane are oppositely charged. Consequently, the effectiveness of ion exchange membrane adsorbers is much more dependent on solution pH when compared to hydrophobic interaction membrane adsorbers. Size based prefiltration was found to be ineffective at disrupting these reversible aggregates. These results can help guide the development of more effective virus filtration processes for monoclonal antibody production. Full article

(This article belongs to the Special Issue Application of Membrane Materials in Bioseparation and Downstream Processing)

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18 pages, 2710 KiB

Open AccessArticle

Reverse Osmosis Coupled with Ozonation for Clean Water Recovery from an Industrial Effluent: Technical and Economic Analyses

by Ivette Montero-Guadarrama, Claudia Muro Urista, Gabriela Roa-Morales, Edith Erialia Gutiérrez Segura, Vianney Díaz-Blancas, Germán Eduardo Dévora-Isiordia and Jesús Álvarez-Sánchez

Membranes 2025, 15(1), 33; https://doi.org/10.3390/membranes15010033 - 16 Jan 2025

Viewed by 569

Abstract

Technical and economic criteria were used to evaluate the feasibility of the treatment of an industrial effluent (10 m³/h) for water recovery and reuse. The treatment evaluation included the following: (1) effluent characteristic determination; (2) selection and evaluation of the effluent [...] Read more.

Technical and economic criteria were used to evaluate the feasibility of the treatment of an industrial effluent (10 m³/h) for water recovery and reuse. The treatment evaluation included the following: (1) effluent characteristic determination; (2) selection and evaluation of the effluent treatment at lab scale, establishing operating conditions and process efficiency; (3) scaling up the treatment process to the industrial level; (4) treatment plant design and commercial availability analysis of the required equipment; and (5) the costs of the inversion and operation of the plant treatment, cost/m³ for water recovery, and time of investment recovery. The physicochemical characteristics of the effluent exposed the polluted wastewater with sodium chloride salts and colourants, predominating a mixture of tartrazine, Red 40, and brilliant blue from the synthesis of food additives. Other contributions of organic compounds and salts could be in minor content. According to the effluent conditions, a coupled process, integrated with ozonation and reverse osmosis, was indicated to be a treatment for water recovery. Scaling up the plant treatment design resulted in 130 m² of area, producing 7.7 m³/h of clean water. The cost of the effluent treatment was 1.4 USD/m³, with an inversion return of 3.4 years and cost investment of USD 860,407. The treatment process resulted a viable project for water recovery. Full article

(This article belongs to the Special Issue Current Research into Membranes in Water Desalination Technology and Engineering)

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14 pages, 3431 KiB

Open AccessArticle

Spacer Designs for Improved Hydrodynamics and Filtration Efficiency in Sea Water Reverse Osmosis

by Sarah Kerdi, Adnan Qamar, Henry J. Tanudjaja and Noreddine Ghaffour

Membranes 2025, 15(1), 32; https://doi.org/10.3390/membranes15010032 - 16 Jan 2025

Viewed by 603

Abstract

Reverse osmosis (RO) filtration performance is heavily influenced by the design of the feed spacer. Spacer design impacts hydrodynamic patterns within the system, affecting water production and concentration polarization. Two spacer designs, namely pillar (P) and standard (S), were investigated to improve the [...] Read more.

Reverse osmosis (RO) filtration performance is heavily influenced by the design of the feed spacer. Spacer design impacts hydrodynamic patterns within the system, affecting water production and concentration polarization. Two spacer designs, namely pillar (P) and standard (S), were investigated to improve the performance of a commercially available spacer design (C) in the RO process. Two approaches were employed to evaluate spacer performance. First, direct numerical simulation (DNS) was utilized to fundamentally understand the hydrodynamics generated by each spacer design. Second, laboratory RO experiments were conducted to confirm the simulation results. The P and S spacers induced higher flow velocity and vorticity than the C spacer, as confirmed by simulations and experiments. Reduced dead zones were also demonstrated using P and S spacers. However, the standard spacer design exhibited a clear advantage in promoting more efficient mixing within the filtration channels. This enhanced mixing substantially reduced salt concentration at the membrane surface, improving the filtration performance. In agreement with the permeation velocity computation, the S spacer achieved the highest improvement (13%) in both flux yield and specific flux relative to the C spacer. This finding confirms the S spacer’s ability to enhance RO performance while reducing energy consumption. Full article

(This article belongs to the Section Membrane Fabrication and Characterization)

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20 pages, 13636 KiB

Open AccessArticle

Cross-Linked Self-Standing Graphene Oxide Membranes: A Pathway to Scalable Applications in Separation Technologies

by Juan A. G. Carrio, Vssl Prasad Talluri, Swamy T. Toolahalli, Sergio G. Echeverrigaray and Antonio H. Castro Neto

Membranes 2025, 15(1), 31; https://doi.org/10.3390/membranes15010031 - 15 Jan 2025

Viewed by 809

Abstract

The large-scale implementation of 2D material-based membranes is hindered by mechanical stability and mass transport control challenges. This work describes the fabrication, characterisation, and testing of self-standing graphene oxide (GO) membranes cross-linked with oxides such as Fe₂O₃, Al₂ [...] Read more.

The large-scale implementation of 2D material-based membranes is hindered by mechanical stability and mass transport control challenges. This work describes the fabrication, characterisation, and testing of self-standing graphene oxide (GO) membranes cross-linked with oxides such as Fe₂O₃, Al₂O₃, CaSO₄, Nb₂O₅, and a carbide, SiC. These cross-linking agents enhance the mechanical stability of the membranes and modulate their mass transport properties. The membranes were prepared by casting aqueous suspensions of GO and SiC or oxide powders onto substrates, followed by drying and detachment to yield self-standing films. This method enabled precise control over membrane thickness and the formation of laminated microstructures with interlayer spacings ranging from 0.8 to 1.2 nm. The resulting self-standing membranes, with areas between 0.002 m² and 0.090 m² and thicknesses from 0.6 μm to 20 μm, exhibit excellent flexibility and retain their chemical and physical integrity during prolonged testing in direct contact with ethanol/water and methanol/water mixtures in both liquid and vapour phases, with stability demonstrated over 24 h and up to three months. Gas permeation and chemical characterisation tests evidence their suitability for gas separation applications. The interactions promoted by the oxides and carbide with the functional groups of GO confer great stability and unique mass transport properties—the Nb₂O₅ cross-linked membranes present distinct performance characteristics—creating the potential for scalable advancements in cross-linked 2D material membranes for separation technologies. Full article

(This article belongs to the Special Issue Graphene Oxide Membrane for Sustainable Energy and Environmental Applications)

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12 pages, 5296 KiB

Open AccessArticle

A Study on the Safety and Efficacy of an Innovative Hydrophilic Dialysis Membrane

by Francisco Maduell, Victor Joaquín Escudero-Saiz, Elena Cuadrado-Payán, Maria Rodriguez-Garcia, Miquel Gómez, Lida María Rodas, Néstor Fontseré, Maria del Carmen Salgado, Gregori Casals, Nayra Rico and José Jesús Broseta

Membranes 2025, 15(1), 30; https://doi.org/10.3390/membranes15010030 - 14 Jan 2025

Viewed by 590

Abstract

The dialysis membrane based on a hydrophilic polymer (Hydrolink NV) was designed to enhance the movement of adsorbed water at the blood–membrane interface, aiming to achieve antithrombogenic and antifouling effects. This study aimed to assess the performance and albumin loss of the Hydrolink [...] Read more.

The dialysis membrane based on a hydrophilic polymer (Hydrolink NV) was designed to enhance the movement of adsorbed water at the blood–membrane interface, aiming to achieve antithrombogenic and antifouling effects. This study aimed to assess the performance and albumin loss of the Hydrolink NV dialyzer in hemodialysis (HD) and post-dilution hemodiafiltration (HDF) with different infusion flows (Qis) and compare it with the hydrophilic FX CorAL dialyzer in post-dilution HDF. A prospective study was carried out in 20 patients. Patients underwent five dialysis sessions with the same routine dialysis parameters: four sessions with the Toraylight NV 2.1 (HD, post-dilution HDF with 50, 75 or auto-substitution Qi) and one with the FX CorAL 800 (post-dilution HDF with auto-substitution Qi). The reduction ratios’ (RRs’) wide range of molecular weight molecules were assessed and the dialysate albumin loss was quantified. The lowest β₂-microglobulin, indoxyl-sulfate, and p-cresyl sulfate RR values were observed with the Toraylight NV 2.1 in HD, and they improved progressively with an increased Qi, without differences being observed between the two dialyzers in auto-substitution. A different removal profile was observed in terms of myoglobin, kFLC, prolactin, α₁-microglobulin, α₁-acid glycoprotein, and λFLC, whose RRs also improved progressively with an increased Qi but were significantly higher with the Toraylight NV than the CorAL in the same convective condition. There were significant differences in the albumin dialysate losses, with the highest value obtained with the Toraylight NV in auto-substitution HDF, with more than 50% of patients surpassing 5 g per session. The Toraylight NV dialyzer has great potential for efficacy but should be used at the optimal convective volume (Qi not exceeding 75 mL/min or FF not exceeding 25%) to avoid excessive albumin loss. Full article

(This article belongs to the Section Membrane Applications for Other Areas)

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23 pages, 1609 KiB

Open AccessReview

Intracellular Membrane Contact Sites in Skeletal Muscle Cells

by Matteo Serano, Stefano Perni, Enrico Pierantozzi, Annunziatina Laurino, Vincenzo Sorrentino and Daniela Rossi

Membranes 2025, 15(1), 29; https://doi.org/10.3390/membranes15010029 - 14 Jan 2025

Viewed by 737

Abstract

Intracellular organelles are common to eukaryotic cells and provide physical support for the assembly of specialized compartments. In skeletal muscle fibers, the largest intracellular organelle is the sarcoplasmic reticulum, a specialized form of the endoplasmic reticulum primarily devoted to Ca²⁺ storage [...] Read more.

Intracellular organelles are common to eukaryotic cells and provide physical support for the assembly of specialized compartments. In skeletal muscle fibers, the largest intracellular organelle is the sarcoplasmic reticulum, a specialized form of the endoplasmic reticulum primarily devoted to Ca²⁺ storage and release for muscle contraction. Occupying about 10% of the total cell volume, the sarcoplasmic reticulum forms multiple membrane contact sites, some of which are unique to skeletal muscle. These contact sites primarily involve the plasma membrane; among these, specialized membrane contact sites between the transverse tubules and the terminal cisternae of the sarcoplasmic reticulum form triads. Triads are skeletal muscle-specific contact sites where Ca²⁺ channels and regulatory proteins assemble to form the so-called calcium release complex. Additionally, the sarcoplasmic reticulum contacts mitochondria to enable a more precise regulation of Ca²⁺ homeostasis and energy metabolism. The sarcoplasmic reticulum and the plasma membrane also undergo dynamic remodeling to allow Ca²⁺ entry from the extracellular space and replenish the stores. This process involves the formation of dynamic membrane contact sites called Ca²⁺ Entry Units. This review explores the key processes in biogenesis and assembly of intracellular membrane contact sites as well as the membrane remodeling that occurs in response to muscle fatigue. Full article

(This article belongs to the Section Biological Membranes)

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2 pages, 283 KiB

Open AccessCorrection

Correction: Robertson et al. Al³⁺ Modification of Graphene Oxide Membranes: Effect of Al Source. Membranes 2022, 12, 1237

by Ellen J. Robertson, Yijing Y. Stehle, Xiaoyu Hu, Luke Kilby, Katelyn Olsson, Minh Nguyen and Rebecca Cortez

Membranes 2025, 15(1), 28; https://doi.org/10.3390/membranes15010028 - 14 Jan 2025

Viewed by 415

Abstract

The authors wish to make a correction to the published paper [...] Full article

13 pages, 5339 KiB

Open AccessArticle

Recovery of Iodine in the Gaseous Phase Using the Silicone Hollow Fiber Membrane Module

by Yoshio Yamabe, Naotake Takahashi, Jun Sawai, Tamotsu Minami, Mikio Kikuchi and Toshimitsu Ishii

Membranes 2025, 15(1), 27; https://doi.org/10.3390/membranes15010027 - 13 Jan 2025

Viewed by 815

Abstract

Iodine, being an important resource, must be recovered and reused. Iodine is not only attracted to the hydrophobic silicone membrane but also easily vaporized. In this study, we explored the use of five types of silicone hollow fiber membrane modules (SFMMs) for separating [...] Read more.

Iodine, being an important resource, must be recovered and reused. Iodine is not only attracted to the hydrophobic silicone membrane but also easily vaporized. In this study, we explored the use of five types of silicone hollow fiber membrane modules (SFMMs) for separating iodine in the gaseous phase. In the SFMM, iodine gas and the recovery solution (sodium sulfite and sodium carbonate at a concentration of 10 mM each) were flowed outside and inside the silicone hollow fiber, respectively, in a co-current-flow manner. At an iodine gas flow rate of 0.2 L/min (8.4 × 10⁻³ mmol-I₂/L), the capture efficiency of iodine into the SFMM was approximately 100% for all five SFMMs. With increasing feed gas flow rates, the capture efficiency of iodine decreased, reducing to approximately 50% at 0.8 L/min. However, the recovery efficiency of iodine in the recovery solution was 60–30% at 0.2–0.8 L/min. This decrease in capture efficiency with increasing flow rates was because iodine could not spread and diffuse successfully in the SFMM, resulting in a low recovery efficiency of iodine. Thus, we next improved the structure of the SFMM by placing a perforated pipe in the center of the module. The perforated pipe effectively directs the iodine feed gas from the holes in the pipe to the hollow fiber membrane bundle wrapped around the pipe. With the improved SFMM, the capture efficiency markedly increased to approximately 100% in the range of the flow rates tested in our experiments. The recovery efficiency also increased to ≥70%. These data illustrate the potential application of the improved SFMM for recovering iodine in the gaseous phase. Full article

(This article belongs to the Special Issue Hollow Fiber Membranes for Gas and Vapor Separation: Fundamentals, State-of-the-Art, and Recent Advancements)

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19 pages, 6147 KiB

Open AccessArticle

Simultaneously Enhanced Permeability and Selectivity of Pebax-1074-Based Mixed-Matrix Membrane for CO₂ Separation

by Rujing Hou, Junwei Xie, Yawei Gu, Lei Wang and Yichang Pan

Membranes 2025, 15(1), 26; https://doi.org/10.3390/membranes15010026 - 13 Jan 2025

Viewed by 565

Abstract

Membrane technology is a promising methodology for carbon dioxide separation due to its benefit of a small carbon footprint. However, the trade-off relationship between gas permeability and selectivity is one obstacle to limiting its application. Herein, branched polyethyleneimine (BPEI) containing a rich amino [...] Read more.

Membrane technology is a promising methodology for carbon dioxide separation due to its benefit of a small carbon footprint. However, the trade-off relationship between gas permeability and selectivity is one obstacle to limiting its application. Herein, branched polyethyleneimine (BPEI) containing a rich amino group was successfully grafted on the surface of the metal–organic framework (MOF) of AIFFIVE-1-Ni (KAUST-8) through coordination between N in BPEI and open metal sites in the MOF and with the resultant maintained BET surface area and pore volume. Both the strengthened CO₂ solubility coefficients coming from the additional CO₂ adsorption sites of amino groups in BPEI and the reinforced CO₂ diffusivity coefficients originating from the fast transport channels created by KAUST-8 led to the promising CO₂ separation performance for KAUST-8@BPEI/Pebax-1074 MMM. With 5 wt.% KAUST-8@BPEI loading, the MMM showed the CO₂ permeability of 156.5 Barrer and CO₂/N₂ selectivity of 16.1, while the KAUST-8-incorporated MMM (5 wt.% loading) only exhibited the CO₂ permeability of 86.9 Barrer and CO₂/N₂ selectivity of 13.0. Such enhancement is superior to most of the reported Pebax-1074-based MMMs for CO₂ separation indicating a wide application for the coordination method for MOF fillers with open metal sites. Full article

(This article belongs to the Special Issue Advanced Membrane Materials for CO₂ Capture and Separation)

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15 pages, 3138 KiB

Open AccessArticle

Large-Area Clay Composite Membranes with Enhanced Permeability for Efficient Dye/Salt Separation

by Yixuan Fu, Shuai Wang, Huiquan Liu, Ke Zhang, Lunxiang Zhang, Yongchen Song and Zheng Ling

Membranes 2025, 15(1), 25; https://doi.org/10.3390/membranes15010025 - 13 Jan 2025

Viewed by 636

Abstract

The escalating discharge of textile wastewater with plenty of dye and salt has resulted in serious environmental risks. Membranes assembled from two-dimensional (2D) nanomaterials with many tunable interlayer spacings are promising materials for dye/salt separation. However, the narrow layer spacing and tortuous interlayer [...] Read more.

The escalating discharge of textile wastewater with plenty of dye and salt has resulted in serious environmental risks. Membranes assembled from two-dimensional (2D) nanomaterials with many tunable interlayer spacings are promising materials for dye/salt separation. However, the narrow layer spacing and tortuous interlayer transport channels of 2D-material-based membranes limit the processing capacity and the permeability of small salt ions for efficient dye/salt separation. In this work, a novel sepiolite/vermiculite membrane was fabricated using Meyer rod-coating and naturally occurring clay. The intercalation of sepiolite Nanofibers between vermiculite Nanosheets provides additional transport nanochannels and forms looser permeable networks, producing composite membranes with remarkably enhanced flux. As a result, the optimized membranes with 80% sepiolite exhibit remarkable flux as high as 78.12 LMH bar⁻¹, outstanding dye rejection (Congo Red~98.26%), and excellent selectivity of dye/salt of 10.41. In addition, this novel all-clay composite membrane demonstrates stable separation performance under acidity, alkalinity and prolonged operation conditions. The large-scale sepiolite/vermiculite membranes made by the simple proposed method using low-cost materials provide new strategies for efficient and environmentally-friendly dye/salt separation. Full article

(This article belongs to the Section Membrane Applications for Water Treatment)

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3 pages, 167 KiB

Open AccessEditorial

Zeolite Membranes for Gas and Liquid Separation: Synthesis and Applications

by Qing Wang, Xiaoyu Yang and Bin Wang

Membranes 2025, 15(1), 24; https://doi.org/10.3390/membranes15010024 - 13 Jan 2025

Viewed by 594

Abstract

The quest for efficient separation technologies is more critical than ever in our rapidly evolving industrial landscape, where the demand for sustainable and cost-effective solutions is paramount [...] Full article

(This article belongs to the Section Membrane Applications for Gas Separation)

21 pages, 10225 KiB

Open AccessArticle

Realization of Intermolecular Interactions as a Basis for Controlling Pervaporation Properties of Membranes Made of Aromatic Polyamide-Imides

by Svetlana V. Kononova, Galina N. Gubanova, Galina K. Lebedeva, Elena V. Kruchinina, Elena N. Vlasova, Elena N. Popova, Natalya V. Zakharova, Milana E. Vylegzhanina, Elena A. Novozhilova and Ksenia V. Danilova

Membranes 2025, 15(1), 23; https://doi.org/10.3390/membranes15010023 - 13 Jan 2025

Viewed by 543

Abstract

New aromatic co-polyamide-imides (coPAIs) containing both carboxyl and hydroxyl groups in the repeating units were synthesized for the first time. Transport, thermal and morphological properties of dense nonporous membranes from PAIs obtained using the diacid chloride of 2-(4-carboxyphenyl)-1,3-dioxoisoindoline-5-carboxylic acid and diamines 5,5′-methylene-bis (2-aminophenol)) [...] Read more.

New aromatic co-polyamide-imides (coPAIs) containing both carboxyl and hydroxyl groups in the repeating units were synthesized for the first time. Transport, thermal and morphological properties of dense nonporous membranes from PAIs obtained using the diacid chloride of 2-(4-carboxyphenyl)-1,3-dioxoisoindoline-5-carboxylic acid and diamines 5,5′-methylene-bis (2-aminophenol)) and 3,5-Diaminobenzoic acid, taken in molar ratios of 7:3, 1:1, and 3:7, have been studied. High levels of membrane permeability accompanied by high selectivity for mixtures of liquids with significantly different polarities were determined by realization of intra- and intermolecular interactions in polymer, which was proved by thermal analyses and hydrodynamic characteristics of coPAIs. This effect is discussed in the context of the effectiveness of intermolecular interactions between polymer chains containing carboxyl and hydroxyl functional groups. Full article

(This article belongs to the Section Membrane Fabrication and Characterization)

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21 pages, 3777 KiB

Open AccessArticle

Separation of Short-Chain Fatty Acids from Primary Sludge into a Particle-Free Permeate by Coupling Chamber Filter-Press and Cross-Flow Microfiltration: Optimization, Semi-Continuous Operation, and Evaluation

by Nikhil Shylaja Prakash, Peter Maurer, Harald Horn, Florencia Saravia and Andrea Hille-Reichel

Membranes 2025, 15(1), 22; https://doi.org/10.3390/membranes15010022 - 11 Jan 2025

Viewed by 760

Abstract

Short-chain fatty acids (SCFAs) are valuable metabolic intermediates that are produced during dark fermentation of sludge, which, when capitalized on, can be used as chemical precursors for biotechnological applications. However, high concentrations of solids with SCFAs in hydrolyzed sludge can be highly detrimental [...] Read more.

Short-chain fatty acids (SCFAs) are valuable metabolic intermediates that are produced during dark fermentation of sludge, which, when capitalized on, can be used as chemical precursors for biotechnological applications. However, high concentrations of solids with SCFAs in hydrolyzed sludge can be highly detrimental to downstream recovery processes. This pilot-scale study addresses this limitation and explores the recovery of SCFAs from primary sludge into a particle-free permeate through a combination of chamber filter-press (material: polyester; mesh size: 100 µm) and cross-flow microfiltration (material: α-Al₂O₃; pore size: 0.2 µm; cross-flow velocity: 3 m∙s⁻¹; pressure = 2.2 bars). Firstly, primary sludge underwent dark fermentation yielding a hydrolyzate with a significant concentration of SCFAs along with total solids (TS) concentration in the range of 20 to 30 g∙L⁻¹. The hydrolyzate was conditioned with hydroxypropyl trimethyl ammonium starch (HPAS), and then dewatered using a filter press, reducing TS by at least 60%, resulting in a filtrate with a suspended solids concentration ranging from 100 to 1300 mg∙L⁻¹. Despite the lower suspended solids concentration, the microfiltration membrane underwent severe fouling due to HPAS’s electrostatic interaction. Two methods were optimized for microfiltration: (1) increased backwashing frequency to sustain a permeate flux of 20 L∙m⁻²∙h⁻¹ (LMH), and (2) surface charge modification to maintain the flux between 70 and 80 LMH. With backwashing, microfiltration can filter around 900 L∙m_eff⁻² (without chemical cleaning), with the flux between 50 and 60 LMH under semi-continuous operation. Evaluating the particle-free permeate obtained from the treatment chain, around 4 gC_SCFAs∙capita⁻¹∙d⁻¹ can be recovered from primary sludge with a purity of 0.85 to 0.97 C_SCFAs∙DOC⁻¹. Full article

(This article belongs to the Section Membrane Applications for Water Treatment)

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16 pages, 1547 KiB

Open AccessArticle

Is Membrane Filtration Applicable for the Recovery of Biologically Active Substances from Spent Lavender?

by Yoana Stoyanova, Nevena Lazarova-Zdravkova and Dimitar Peshev

Membranes 2025, 15(1), 21; https://doi.org/10.3390/membranes15010021 - 11 Jan 2025

Viewed by 503

Abstract

This study explored the batch membrane filtration of 40% ethanol extracts from spent lavender, containing valuable compounds like rosmarinic acid, caffeic acid, and luteolin, using a polyamide-urea thin film composite X201 membrane. Conducted at room temperature and 20 bar transmembrane pressure, the process [...] Read more.

This study explored the batch membrane filtration of 40% ethanol extracts from spent lavender, containing valuable compounds like rosmarinic acid, caffeic acid, and luteolin, using a polyamide-urea thin film composite X201 membrane. Conducted at room temperature and 20 bar transmembrane pressure, the process demonstrated high efficiency, with rejection rates exceeding 98% for global antioxidant activity and 93–100% for absolute concentrations of the target components. During concentration, the permeate flux declined from 2.43 to 1.24 L·m⁻²·h⁻¹ as the permeate-to-retentate-volume ratio increased from 0 to 1. The process resistance, driven by osmotic pressure and concentration polarization, followed a power–law relationship with a power value of 1.20, consistent with prior nanofiltration studies of rosmarinic acid solutions. Notably, no membrane fouling occurred, confirming the method’s scalability without compromising biological activity. The antioxidant activity, assessed via the DPPH method, revealed that the retentate exhibited double the activity of the feed. Antibacterial assays using broth microdilution showed that the retentate inhibited Escherichia coli by 73–96% and Bacillus subtilis by 97–98%, making it the most active fraction. These findings validate the effectiveness of the X201 membrane for concentrating natural antioxidants and antibacterial agents from lavender extract under sustainable operating conditions. Full article

(This article belongs to the Special Issue Advancements in Membrane Technologies for Resource Recovery)

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26 pages, 8557 KiB

Open AccessArticle

A Structural Bioinformatics-Guided Study of Adenosine Triphosphate-Binding Cassette (ABC) Transporters and Their Substrates

by Iqra Younus, Robert C. Ford and Stephen M. Prince

Membranes 2025, 15(1), 20; https://doi.org/10.3390/membranes15010020 - 10 Jan 2025

Viewed by 573

Abstract

Adenosine triphosphate-binding cassette (ABC) transporters form a ubiquitous superfamily of integral membrane proteins involved in the translocation of substrates across membranes. Human ABC transporters are closely linked to the pathogenesis of diseases such as cancer, metabolic diseases, and Alzheimer’s disease. In this study, [...] Read more.

Adenosine triphosphate-binding cassette (ABC) transporters form a ubiquitous superfamily of integral membrane proteins involved in the translocation of substrates across membranes. Human ABC transporters are closely linked to the pathogenesis of diseases such as cancer, metabolic diseases, and Alzheimer’s disease. In this study, four ABC transporters were chosen based on (I) their importance in humans and (II) their score in a structural bioinformatics screen aimed at the prediction of crystallisation propensity. The top-scoring ABC transporters’ orthologs (Mus musculus—mouse ABCB5, Ailuropoda melanoleuca—giant panda ABCB6, Myotis lucifugus—little brown bat ABCG1 and Mus musculus ABCG4) were then expressed in Saccharomyces cerevisiae with a combined green fluorescent protein and polyhistidine tag, enabling visualisation and purification. After partial purification and in the presence of the detergent (n-dodecyl-β-D-maltoside), the kinetic parameters of the ATP hydrolysis reactions of the orthologs were determined, as well as the extent of stimulation of their activity when presented with putative substrates. We discuss the efficiency of such bioinformatics approaches and make suggestions for their improvement and wider application in membrane protein-structure determination. Full article

(This article belongs to the Section Biological Membranes)

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15 pages, 5276 KiB

Open AccessArticle

ZIF-8-Embedded Cation-Exchange Membranes with Improved Monovalent Ion Selectivity for Capacitive Deionization

by Eui-Gyu Han, Ji-Hyeon Lee and Moon-Sung Kang

Membranes 2025, 15(1), 19; https://doi.org/10.3390/membranes15010019 - 9 Jan 2025

Viewed by 769

Abstract

Membrane capacitive deionization (MCDI) is an electrochemical ion separation process that combines ion-exchange membranes (IEMs) with porous carbon electrodes to enhance desalination efficiency and address the limitations of conventional capacitive deionization (CDI). In this study, a cation-exchange membrane (CEM) embedded with a metal–organic [...] Read more.

Membrane capacitive deionization (MCDI) is an electrochemical ion separation process that combines ion-exchange membranes (IEMs) with porous carbon electrodes to enhance desalination efficiency and address the limitations of conventional capacitive deionization (CDI). In this study, a cation-exchange membrane (CEM) embedded with a metal–organic framework (MOF) was developed to effectively separate monovalent and multivalent cations in influent solutions via MCDI. To fabricate CEMs with high monovalent ion selectivity, ZIF-8 was incorporated into sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) at various weight ratios. The resulting membranes were systematically characterized using diverse electrochemical methods. The ZIF-8-embedded CEMs demonstrated a sieving effect based on differences in ion size and hydration energy, achieving excellent permselectivity for monovalent ions. MCDI tests using the prepared CEMs showed a Na⁺ ion removal rate exceeding 99% in Na⁺/Mg²⁺ and Na⁺/Ca²⁺ mixed feed solutions, outperforming a commercial membrane (CSE, Astom Corp., Tokyo, Japan), which achieved a removal rate of 94.1%. These findings are expected to provide valuable insights for advancing not only MCDI but also other electro-membrane processes capable of selectively separating specific ions. Full article

(This article belongs to the Section Membrane Applications for Water Treatment)

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17 pages, 1457 KiB

Open AccessArticle

Membrane Treatment to Improve Water Recycling in an Italian Textile District

by Francesca Tuci, Michele Allocca, Donatella Fibbi, Daniele Daddi and Riccardo Gori

Membranes 2025, 15(1), 18; https://doi.org/10.3390/membranes15010018 - 9 Jan 2025

Viewed by 572

Abstract

The textile district of Prato (Italy) has developed a wastewater recycling system of considerable scale. The reclaimed wastewater is characterized by high levels of hardness (32 °F on average), which precludes its direct reuse in numerous wet textile processes (e.g., textile dyeing). Consequently, [...] Read more.

The textile district of Prato (Italy) has developed a wastewater recycling system of considerable scale. The reclaimed wastewater is characterized by high levels of hardness (32 °F on average), which precludes its direct reuse in numerous wet textile processes (e.g., textile dyeing). Consequently, these companies utilize ion exchange resins for water softening. However, the regeneration of the resins results in an increased concentration of chlorides in the reclaimed wastewater that exceeds the limit set by Italian regulations for the reuse of water for irrigation purposes. The objective of this study is to investigate the potential of membrane filtration as an alternative method for removing hardness from water. Therefore, an industrial-scale ultrafiltration-nanofiltration (UF-NF) pilot plant was installed to test the rejection of hardness from the reclaimed wastewater. The experiment employed two types of NF membranes and three permeate fluxes (27, 35, and 38 L·m⁻²·h⁻¹) for testing. The results demonstrated that the system could remove hardness with efficiencies exceeding 98% under all conditions tested. The experimental findings indicate that the UF-NF system has the potential to be employed as a post-treatment step to render the reclaimed wastewater suitable for all textile finishing processes and to expand the scope for reuse. Full article

(This article belongs to the Section Membrane Applications for Water Treatment)

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42 pages, 3563 KiB

Open AccessReview

A Review of Sulfate Removal from Water Using Polymeric Membranes

by Jamal Al Mehrate, Sadek Shaban and Amr Henni

Membranes 2025, 15(1), 17; https://doi.org/10.3390/membranes15010017 - 9 Jan 2025

Viewed by 580

Abstract

Access to clean and reliable water has become a critical concern due to the global water crisis. High sulfate levels in drinking water raise health concerns for humans and animals and can cause serious corrosion in industrial systems. Sulfated waters represent a major [...] Read more.

Access to clean and reliable water has become a critical concern due to the global water crisis. High sulfate levels in drinking water raise health concerns for humans and animals and can cause serious corrosion in industrial systems. Sulfated waters represent a major challenge on the Canadian prairies, leading to many cattle deaths. While reverse osmosis (RO) membranes effectively remove sulfates, they are costly due to high-pressure requirements. Nanofiltration (NF) membranes present a more affordable alternative, outperforming traditional methods like adsorption, desalination, and ion exchange. Developing low-pressure ultrafiltration (UF) and microfiltration (MF) membranes could also reduce costs. This review explores advancements in polymeric materials and membrane technology to enhance sulfate removal, focusing on methods used to reduce fouling and improve permeate flux. Techniques discussed include phase inversion (PI), thin-film composite (TFC), and thin-film nanocomposite (TFN) membranes. The review also highlights recent fabrication methods for pristine and nanomaterial-enhanced membranes, acknowledging both benefits and limitations. Continued innovations in polymer-based membranes are expected to drive further performance and cost-efficiency improvements. This review found that studies in the literature dealt mainly with sulfate concentrations below 2000 mg/L, indicating a need to address higher concentrations in future studies. Full article

(This article belongs to the Special Issue Membrane Separation and Water Treatment: Modeling and Application)

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23 pages, 9631 KiB

Open AccessArticle

Development of Hollow Fiber Membranes Suitable for Outside-In Filtration of Human Blood Plasma

by David Ramada, Bente Adema, Mohamed Labib, Odyl ter Beek and Dimitrios Stamatialis

Membranes 2025, 15(1), 16; https://doi.org/10.3390/membranes15010016 - 9 Jan 2025

Viewed by 557

Abstract

Hemodialysis (HD) is a critical treatment for patients with end-stage kidney disease (ESKD). The effectiveness of conventional dialyzers used there could be compromised during extended use due to limited blood compatibility of synthetic polymeric membranes and sub-optimal dialyzer design. In fact, blood flow [...] Read more.

Hemodialysis (HD) is a critical treatment for patients with end-stage kidney disease (ESKD). The effectiveness of conventional dialyzers used there could be compromised during extended use due to limited blood compatibility of synthetic polymeric membranes and sub-optimal dialyzer design. In fact, blood flow in the hollow fiber (HF) membrane could trigger inflammatory responses and thrombus formation, leading to reduced filtration efficiency and limiting therapy duration, a consequence of flowing the patients’ blood through the lumen of each fiber while the dialysate passes along the inter-fiber space (IOF, inside-out filtration). This study investigates the development of HF membranes for “outside-in filtration” (OIF) in HD. In OIF, blood flows through the inter-fiber space while dialysate flows within the fiber lumens, reducing the risk of fiber clogging and potentially extending treatment duration. For the OIF mode, the membrane should have a blood-compatible outer selective layer in contact with the patient’s blood. We develop HFs for OIF via liquid-induced phase separation using PES/PVP (polyethersulphone/polyvinylpyrrolidone) blends. The fibers’ surface morphology (SEM, scanning electron microscopy), chemistry (ATR-FTIR—attenuated total reflection-Fourier transform infrared spectroscopy, XPS—X-ray photoelectron spectroscopy), transport properties, and uremic toxin removal from human plasma are evaluated and compared to commercial HFs. These membranes feature a smooth, hydrophilic outer layer, porous lumen, ultrafiltration coefficient of 13–34 mL m² h⁻¹ mmHg⁻¹, adequate mechanical properties, low albumin leakage, and toxin removal performance on par with commercial membranes in IOF and OIF. They offer potential for more efficient long-term HD by reducing clogging and systemic anticoagulation needs and enhancing treatment time and toxin clearance. Full article

(This article belongs to the Section Membrane Applications for Other Areas)

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14 pages, 3333 KiB

Open AccessArticle

Circular Economy Applied to Sludge Minimization: The STAR Project

by Maria Cristina Collivignarelli, Stefano Bellazzi and Alessandro Abbà

Membranes 2025, 15(1), 15; https://doi.org/10.3390/membranes15010015 - 9 Jan 2025

Viewed by 403

Abstract

The management of biological sludge from wastewater treatment plants (WWTPs) poses a significant environmental challenge due to increasing sludge production and the presence of emerging pollutants. This study investigates an innovative solution by integrating a thermophilic aerobic membrane reactor (TAMR) into the sludge [...] Read more.

The management of biological sludge from wastewater treatment plants (WWTPs) poses a significant environmental challenge due to increasing sludge production and the presence of emerging pollutants. This study investigates an innovative solution by integrating a thermophilic aerobic membrane reactor (TAMR) into the sludge treatment line of a medium-size WWTP, aiming to minimize biological sludge output while enhancing resource recovery. The study involved a six-month monitoring of an industrial-scale TAMR system, assessing the reduction in volatile solids (VSs) in thickened sludge and evaluating the compatibility of TAMR residues with conventional activated sludge (CAS) systems. The TAMR unit, which achieved up to a 90% reduction in VSs, was combined with traditional CAS processes, forming the STAR (Sludge Treatment and Advanced Recycling) configuration. This configuration reduced sludge output to just 10% of conventional levels while enabling the recirculation of nutrient-rich liquid effluents. Both batch and continuous respirometric tests demonstrated the biological treatability of TAMR residues, highlighting their potential reuse as external carbon sources and their positive impact on CAS system performance. The findings suggest that integrating mesophilic and thermophilic systems can significantly improve sludge management efficiency, lowering both operating costs and environmental impacts. Full article

(This article belongs to the Special Issue Green Membrane Technologies: Advancements in Materials and Energy Efficiency for Water Treatment)

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14 pages, 516 KiB

Open AccessReview

The Role of Membranes in Modern Winemaking: From Clarification to Dealcoholization

by Carolina E. Demaman Oro, Bruna M. Saorin Puton, Luciana D. Venquiaruto, Rogério Marcos Dallago, Giordana Demaman Arend and Marcus V. Tres

Membranes 2025, 15(1), 14; https://doi.org/10.3390/membranes15010014 - 9 Jan 2025

Viewed by 524

Abstract

The utilization of membrane technologies in winemaking has revolutionized various stages of production, offering precise and efficient alternatives to traditional methods. Membranes, characterized by their selective permeability, play a pivotal role in enhancing wine quality across multiple processes. In clarification, microfiltration and ultrafiltration [...] Read more.

The utilization of membrane technologies in winemaking has revolutionized various stages of production, offering precise and efficient alternatives to traditional methods. Membranes, characterized by their selective permeability, play a pivotal role in enhancing wine quality across multiple processes. In clarification, microfiltration and ultrafiltration membranes, such as ceramic or polymeric membranes (e.g., polyethersulfone or PVDF), effectively remove suspended solids and colloids, resulting in a clearer wine without the need for chemical agents. During stabilization, membranes such as nanofiltration and reverse osmosis membranes, often made from polyamide composite materials, enable the selective removal of proteins, polysaccharides, and microorganisms, thereby improving the wine’s stability and extending its shelf life. Additionally, in dealcoholization, membranes like reverse osmosis and pervaporation membranes, typically constructed from polydimethylsiloxane (PDMS) or other specialized polymers, facilitate the selective removal of ethanol while preserving the wine’s flavor and aroma profile, addressing the increasing consumer demand for low-alcohol and alcohol-free wines. This article provides a comprehensive analysis of the advancements and applications of membrane technologies in winemaking. Full article

(This article belongs to the Special Issue Membrane Technologies in Food Processing)

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30 pages, 3564 KiB

Open AccessReview

A Critical Review of the Hydrometallurgy and Pyrometallurgical Recovery Processes of Platinum Group Metals from End-of-Life Fuel Cells

by Sinikiwe A. Mvokwe, Opeoluwa O. Oyedeji, Mojeed A. Agoro, Edson L. Meyer and Nicholas Rono

Membranes 2025, 15(1), 13; https://doi.org/10.3390/membranes15010013 - 8 Jan 2025

Viewed by 581

Abstract

Recently, the recovery of metals extracted from the spent membrane electrode assemblies (MEAs) of fuel cells has attracted significant scientific attention due to its detrimental environmental impacts. Two major approaches, i.e., pyrometallurgical and hydrometallurgical, have been explored to recover platinum group metals (PMGs) [...] Read more.

Recently, the recovery of metals extracted from the spent membrane electrode assemblies (MEAs) of fuel cells has attracted significant scientific attention due to its detrimental environmental impacts. Two major approaches, i.e., pyrometallurgical and hydrometallurgical, have been explored to recover platinum group metals (PMGs) from used proton exchange membrane fuel cells (PEMFCs). However, the efficacy of these methods has been limited by the low concentrations of the metals and the high costs involved. Essentially, pyrometallurgical processes result in the evolution of harmful gases. Thus, the hydrometallurgical process is preferred as a suitable alternative. In this review, an overview of the application of pyrometallurgical and hydrometallurgical methods in the recovery of PGMs is presented. The health risks, benefits, and limitations of these processes are highlighted. Finally, the hurdles faced by, opportunities for, and future directions of these approaches are identified. It is envisaged that this review will shed light on the current status of processes for the recovery of spent PGMs and propel their advancement for effective recycling strategies. Full article

(This article belongs to the Section Membrane Applications for Energy)

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18 pages, 3722 KiB

Open AccessArticle

Supercapacitor Cell Performance with Bacterial Nanocellulose and Bacterial Nanocellulose/Polybenzimidazole Impregnated Membranes as Separator

by Hristo Penchev, Galia Ivanova, Venelin Hubenov, Ivanka Boyadzieva, Desislava Budurova, Filip Ublekov, Adriana Gigova and Antonia Stoyanova

Membranes 2025, 15(1), 12; https://doi.org/10.3390/membranes15010012 - 8 Jan 2025

Viewed by 651

Abstract

Supercapacitors are advanced energy storage devices renowned for their rapid energy delivery and long operational lifespan, making them indispensable across various industries. Their relevance has grown in recent years due to the adoption of environmentally friendly materials. One such material is bacterial nanocellulose [...] Read more.

Supercapacitors are advanced energy storage devices renowned for their rapid energy delivery and long operational lifespan, making them indispensable across various industries. Their relevance has grown in recent years due to the adoption of environmentally friendly materials. One such material is bacterial nanocellulose (BNC), produced entirely from microbial sources, offering sustainability and a bioprocess-driven synthesis. In this study, BNC was synthesized using a symbiotic microbial community. After production and purification, pristine BNC membranes, with an average thickness of 80 microns, were impregnated with an alkali-alcohol meta-polybenzimidazole (PBI) solution. This process yielded hybrid BNC/PBI membranes with improved ion-transport properties. The BNC membranes were then doped with a 6 M KOH solution, to enhance OH⁻ conductivity, and characterized using optical microscopy, ATR FT-IR, XRD, CVT, BET analysis, and impedance spectroscopy. Both BNC and BNC/PBI membranes were tested as separators in laboratory-scale symmetric supercapacitor cells, with performance compared to a commercial Viledon^® separator. The supercapacitors employing BNC membranes exhibited high specific capacitance and excellent cycling stability, retaining performance over 10,000 charge/discharge cycles. These findings underscore the potential of BNC/KOH membranes for next-generation supercapacitor applications. Full article

(This article belongs to the Section Membrane Applications for Energy)

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22 pages, 4065 KiB

Open AccessArticle

Inertial Memory Effects in Molecular Transport Across Nanoporous Membranes

by Slobodanka Galovic, Milena Čukić and Dalibor Chevizovich

Membranes 2025, 15(1), 11; https://doi.org/10.3390/membranes15010011 - 6 Jan 2025

Viewed by 574

Abstract

Nanoporous membranes are heterogeneous structures, with heterogeneity manifesting at the microscale. In examining particle transport through such media, it has been observed that this transport deviates from classical diffusion, as described by Fick’s second law. Moreover, the classical model is physically unsustainable, as [...] Read more.

Nanoporous membranes are heterogeneous structures, with heterogeneity manifesting at the microscale. In examining particle transport through such media, it has been observed that this transport deviates from classical diffusion, as described by Fick’s second law. Moreover, the classical model is physically unsustainable, as it is non-causal and predicts an infinite speed of concentration perturbation propagation through a substantial medium. In this work, we have derived two causal models as extensions of Fick’s second law, where causality is linked to the effects of inertial memory in the nanoporous membrane. The results of the derived models have been compared with each other and with those obtained from the classical model. It has been demonstrated that both causal models, one with exponentially fading inertial memory and the other with power-law fading memory, predict that the concentration perturbation propagates as a damped wave, leading to an increased time required for the cumulative amount of molecules passing through the membrane to reach a steady state compared to the classical model. The power-law fading memory model predicts a longer time required to achieve a stationary state. These findings have significant implications for understanding cell physiology, developing drug delivery systems, and designing nanoporous membranes for various applications. Full article

(This article belongs to the Section Membrane Fabrication and Characterization)

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12 pages, 1425 KiB

Open AccessArticle

Chemical and Sensory Evaluation of Blackberry (Rubus sp.) Juice Concentrated by Reverse Osmosis and Osmotic Evaporation

by Juliana Vilar, Flavia Monteiro, Luiz Corrêa-Filho, Flávia Gomes, Renata Tonon, Daniela Freitas-Sá, Suely Freitas and Lourdes Cabral

Membranes 2025, 15(1), 10; https://doi.org/10.3390/membranes15010010 - 6 Jan 2025

Viewed by 670

Abstract

Blackberry can be considered a source of phenolic compounds with antioxidant properties, especially anthocyanins, which are responsible for the attractive color of the juice. However, blackberry juice quality can be reduced under severe heat treatments, resulting in darkened color and altered taste. Membrane [...] Read more.

Blackberry can be considered a source of phenolic compounds with antioxidant properties, especially anthocyanins, which are responsible for the attractive color of the juice. However, blackberry juice quality can be reduced under severe heat treatments, resulting in darkened color and altered taste. Membrane separation processes are an alternative for the clarification and concentration of fruit juices, with advantages as the maintenance of the nutritional, sensory, and functional characteristics of the product. The aim of this work was to evaluate the effect of membrane concentration on the physicochemical and sensory characteristics of blackberry juice. The juice was first clarified by an enzymatic treatment associated with microfiltration and then concentrated by reverse osmosis and osmotic evaporation. Samples were analyzed for pH, titratable acidity, soluble and total solids, phenolic content, antioxidant activity, and total anthocyanins. The concentrated juices were then reconstituted for sensory evaluation. It was verified that reverse osmosis and osmotic evaporation resulted in juices with total solid concentrations of 29 and 53 g∙100 g⁻¹, respectively, with slight differences in pH and acidity. Some phenolic compounds were lost during processing. The concentration of anthocyanins and the antioxidant capacity of the osmotic evaporation-concentrated juice increased 6.2 and 7.7 times, respectively, compared to the initial juice. Regarding sensory analysis, the juices concentrated by RO and EO presented acceptance percentages (scores between 6 and 9) of 58% and 55%, respectively. Consumers described them as “good appearance”, “refreshing”, “tasty”, “sweet”, or “with ideal sweetness”, in agreement with the high acceptance scores (6.2 and 6.9, respectively). Full article

(This article belongs to the Special Issue Membrane Technologies in Food Processing)

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14 pages, 6671 KiB

Open AccessArticle

A STEDable BF₂-Azadipyrromethene Fluorophore for Nuclear Membrane and Associated Endoplasmic Reticulum Imaging

by Anaïs C. Bourgès, Massimiliano Garre, Dan Wu and Donal F. O’Shea

Membranes 2025, 15(1), 9; https://doi.org/10.3390/membranes15010009 - 1 Jan 2025

Viewed by 706

Abstract

The endoplasmic reticulum and the internal nuclear compartments are intrinsically connected through the nuclear membrane, pores and lamina. High resolution imaging of each of these cellular features concurrently remains a significant challenge. To that end we have developed a new molecular nuclear membrane-endoplasmic [...] Read more.

The endoplasmic reticulum and the internal nuclear compartments are intrinsically connected through the nuclear membrane, pores and lamina. High resolution imaging of each of these cellular features concurrently remains a significant challenge. To that end we have developed a new molecular nuclear membrane-endoplasmic reticulum (NM-ER) staining fluorophore with emission maxima at 650 nm. NM-ER is compatible with fixed and live cell imaging and stimulated emission depletion microscopy (STED) showing significant improvement in resolution when compared to comparable confocal laser scanning microscopy. The imaging versatility of NM-ER was illustrated through its compatible use with other fluorophores for co-imaging with DNA, nuclear pores and lamina allowing cellular abnormalities to be identified. NM-ER alone, or in use with other nuclear region labels could be an important tool for the investigation of nuclear transport and associated cellular processes. Full article

(This article belongs to the Section Biological Membranes)

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17 pages, 4253 KiB

Open AccessReview

UiO-66 Metal-Organic Framework Membranes: Structural Engineering for Separation Applications

by Yanwei Sun

Membranes 2025, 15(1), 8; https://doi.org/10.3390/membranes15010008 - 1 Jan 2025

Viewed by 1147

Abstract

Metal-organic frameworks (MOFs) have been recognized as promising materials for membrane-based separation technologies due to their exceptional porosity, structural tunability, and chemical stability. This review presents a comprehensive discussion of the advancements in structure engineering and design strategies that have been employed to [...] Read more.

Metal-organic frameworks (MOFs) have been recognized as promising materials for membrane-based separation technologies due to their exceptional porosity, structural tunability, and chemical stability. This review presents a comprehensive discussion of the advancements in structure engineering and design strategies that have been employed to optimize UiO-66 membranes for enhanced separation performance. Various synthesis methods for UiO-66 membranes are explored, with a focus on modulated approaches that incorporate different modulators to fine-tune nucleation rates and crystallization processes. The influence of preferred orientation, membrane thickness, pore size, pore surface chemistry, and hierarchical structures on the separation performance is concluded. By providing a consolidated overview of current research efforts and future directions in UiO-66 membrane development, this review aims to inspire further advancements in the field of separation technologies. Full article

(This article belongs to the Special Issue Recent Developments in Metal-Organic Framework Membranes)

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24 pages, 7437 KiB

Open AccessArticle

Investigation of the Ternary System, Water/Hydrochloric Acid/Polyamide 66, for the Production of Polymeric Membranes by Phase Inversion

by Jocelei Duarte, Camila Suliani Raota, Camila Baldasso, Venina dos Santos and Mara Zeni

Membranes 2025, 15(1), 7; https://doi.org/10.3390/membranes15010007 - 1 Jan 2025

Viewed by 767

Abstract

The starting point for the preparation of polymeric membranes by phase inversion is having a thermodynamically stable solution. Ternary diagrams for the polymer, solvent, and non-solvent can predict this stability by identifying the phase separation and describing the thermodynamic behavior of the membrane [...] Read more.

The starting point for the preparation of polymeric membranes by phase inversion is having a thermodynamically stable solution. Ternary diagrams for the polymer, solvent, and non-solvent can predict this stability by identifying the phase separation and describing the thermodynamic behavior of the membrane formation process. Given the lack of data for the ternary system water (H₂O)/hydrochloric acid (HCℓ)/polyamide 66 (PA66), this work employed the Flory–Huggins theory for the construction of the ternary diagrams (H₂O/HCℓ/PA66 and H₂O/formic acid (FA)/PA66) by comparing the experimental data with theoretical predictions. Pure polymer and the membranes produced by phase inversion were characterized to provide the information required to create the ternary diagrams. PA66/FA and PA66/HCℓ solutions were also evaluated regarding their classification as true solutions, and the universal quasi-chemical functional group activity coefficient (UNIFAC) method was used for determining non-solvent/solvent interaction parameters (g₁₂). Swelling measurements determined the polymer/non-solvent interaction parameter (χ₁₃) for H₂O/PA66 and the solvent/polymer interaction parameter (χ₂₃) for PA66/FA and PA66/HCℓ. The theoretical cloud point curve was calculated based on “Boom’s LCP Correlation” and compared to the curve of the experimental cloud point. The ternary Gibbs free energy of mixing and χ₂₃ indicated FA as the best solvent for the PA66. However, for HCℓ, the lower concentration (37–38%), volatility, and fraction volume of dissolved PA66 (ϕ₃) indicated that HCℓ is also adequate for PA66 solubilization based on the similar membrane morphology observed when compared to the PA66/FA membrane. Full article

(This article belongs to the Special Issue The Thin-Film Composite Membrane: Principles, Productions and Applications)

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