Membrane Arrangements Research Articles

Application of Principal Component Analysis for the Elucidation of Operational Features for Pervaporation Desalination Performance of PVA-Based TFC Membrane

Principal Component Analysis (PCA) serves as a valuable tool for analyzing membrane processes, offering insights into complex datasets, identifying crucial factors influencing membrane performance, aiding in design and optimization, and facilitating monitoring and fault diagnosis. In this study, PCA is applied to understand operational features affecting pervaporation desalination performance of PVA-based TFC membranes. PCA-biplot representation reveals that the first two principal components (PCs) accounted for 62.34% of the total variance, with normalized permeation with selective layer thickness (Pnorm), water permeation flux (P), and operational temperature (T) contributing significantly to PC1, while salt rejection dominates PC2. Membrane clustering indicates distinct influences, with membranes grouped based on correlation with operational factors. Excluding outliers increases total variance to 74.15%, showing altered membrane arrangements. Interestingly, the adopted strategy showed a high discrepancy between P and Pnorm, indicating the relevance of comparing between PVA membranes with specific layers and those with none. PCA results showed that Pnorm is more important than P in operational features, highlighting its significance in both research and practical applications. Our findings show that even know P remains a key performance property; Pnorm is critical for developing high-performance, efficient, and economically viable pervaporation desalination membranes. Subsequent PCA for membranes without specific layers (M1 to M6) and with specific layers (M7 to M11) highlights higher total variance and influence of variables, aiding in understanding membranes’ behavior and suitability under different conditions. Overall, PCA effectively delineates performance characteristics and potential applications of PVA-based TFC membranes. This study would confirm the applicability of the PCA approach in monitoring the operational efficiency of pervaporation desalination via these membranes.

Design and multiobjective optimization of membrane steam methane reformer: A computational fluid dynamic analysis

A membrane reactor affords promising advantages for processes; however, it faces many issues such as the high cost, manufacturing complexity, and ineffective zones. In this numerical analysis, we propose a design and multiobjective optimization of membrane steam methane reforming reactor to attain an effective arrangement for high hydrogen yield and separation. Four configurations were investigated for comparative analysis, adopting continuous and segmented catalyst and membrane arrangements; thereafter, the genetic algorithm optimization approach was applied. The advantages of the proposed membrane and catalyst design were shown and justified. Compared to the conventional case, the results showed high hydrogen yield and separation in the design case, despite the significant reduction in the Pd membrane length. For the optimal case, further improvement of the hydrogen separation and high hydrogen yield were achieved with 20% less catalyst load and an 80% reduction in the membrane length as the membrane was effectively embedded, which can significantly reduce the cost of the process. Furthermore, the complexity of the membrane reactor was avoided as the reaction and the separation were conducted separately.

Assembly of tetraspanins, galectin-3, and distinct N-glycans defines the solubilization signature of seminal prostasomes from normozoospermic and oligozoospermic men.

BackgroundProstasomes, extracellular vesicles (EVs) abundantly present in seminal plasma, express distinct tetraspanins (TS) and galectin-3 (gal-3), which are supposed to shape their surface by an assembly of different molecular complexes. In this study, detergent-sensitivity patterns of membrane-associated prostasomal proteins were determined aiming at the solubilization signature as an intrinsic multimolecular marker and a new parameter suitable as a reference for the comparison of EVs populations in health and disease.MethodsProstasomes were disrupted by Triton X-100 and analyzed by gel filtration under conditions that maintained complete solubilization. Redistribution of TS (CD63, CD9, and CD81), gal-3, gamma-glutamyltransferase (GGT), and distinct N-glycans was monitored using solid-phase lectin-binding assays, transmission electron microscopy, electrophoresis, and lectin blot.ResultsComparative data on prostasomes under normal physiology and conditions of low sperm count revealed similarity regarding the redistribution of distinct N-glycans and GGT, all presumed to be mainly part of the vesicle coat. In contrast to this, a greater difference was found in the redistribution of integral membrane proteins, exemplified by TS and gal-3. Accordingly, they were grouped into two molecular patterns mainly consisting of overlapped CD9/gal-3/wheat germ agglutinin-reactive glycoproteins and CD63/GGT/concanavalin A-reactive glycoproteins.ConclusionsSolubilization signature can be considered as an all-inclusive distinction factor regarding the surface properties of a particular vesicle since it reflects the status of the parent cell and the extracellular environment, both of which contribute to the composition of spatial membrane arrangements.

Ionic environment, thickness and line tension as determinants of phase separation in whole Purified Myelin Membranes monolayers

Purified myelin membranes (PMM) were spread as monomolecular films at the air/aqueous solution interface, and visualized by Brewster Angle Microscopy (BAM) at different lateral pressures (π) on three specific aqueous solutions: absence of salts, physiological conditions and presence of calcium. Coexistence of Liquid-Expanded (LE) and Liquid Ordered (LO) phases persisted up to collapse in the presence of salts, whereas monolayers became homogeneous at π ≥ 35−40 mN/m when salts are absent. This PMM phase-mixing behavior in monolayers is similar to the previously reported behavior of PMM multilamellar vesicles. Reflectivities (Rp) of p-polarized light from both phases were assessed throughout the whole π -range, and film thicknesses (t) were calculated from the Rp values and measured film refractive indices (n). The LO phase was found to be more reflective and thicker than the LE phase at π ≤ 15 mN/m, but less reflective and thinner at higher π.We also determined the line tension (λ) of PMM monolayers at the domain boundaries from the rate of domain shape relaxation, which turned out to be of the order of picoNewtons (pN) and decreased as π increased. A correlation between λ and thickness differences (Δt) was found, suggesting that Δt is a molecular determinant for λ in PMM monolayers.Both λ and Δt were found to increase markedly when calcium was present in the subphase. This result corroborates the concept of divalent cations as a stabilizing factor for phase separation, in line with earlier studies on this mixture forming multilamellar membrane arrangements.

Small-Angle X-Ray and Neutron Scattering on Photosynthetic Membranes.

Ultrastructural membrane arrangements in living cells and their dynamic remodeling in response to environmental changes remain an area of active research but are also subject to large uncertainty. The use of noninvasive methods such as X-ray and neutron scattering provides an attractive complimentary source of information to direct imaging because in vivo systems can be probed in near-natural conditions. However, without solid underlying structural modeling to properly interpret the indirect information extracted, scattering provides at best qualitative information and at worst direct misinterpretations. Here we review the current state of small-angle scattering applied to photosynthetic membrane systems with particular focus on data interpretation and modeling.

The SARS-Coronavirus Infection Cycle: A Survey of Viral Membrane Proteins, Their Functional Interactions and Pathogenesis.

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is a novel epidemic strain of Betacoronavirus that is responsible for the current viral pandemic, coronavirus disease 2019 (COVID-19), a global health crisis. Other epidemic Betacoronaviruses include the 2003 SARS-CoV-1 and the 2009 Middle East Respiratory Syndrome Coronavirus (MERS-CoV), the genomes of which, particularly that of SARS-CoV-1, are similar to that of the 2019 SARS-CoV-2. In this extensive review, we document the most recent information on Coronavirus proteins, with emphasis on the membrane proteins in the Coronaviridae family. We include information on their structures, functions, and participation in pathogenesis. While the shared proteins among the different coronaviruses may vary in structure and function, they all seem to be multifunctional, a common theme interconnecting these viruses. Many transmembrane proteins encoded within the SARS-CoV-2 genome play important roles in the infection cycle while others have functions yet to be understood. We compare the various structural and nonstructural proteins within the Coronaviridae family to elucidate potential overlaps and parallels in function, focusing primarily on the transmembrane proteins and their influences on host membrane arrangements, secretory pathways, cellular growth inhibition, cell death and immune responses during the viral replication cycle. We also offer bioinformatic analyses of potential viroporin activities of the membrane proteins and their sequence similarities to the Envelope (E) protein. In the last major part of the review, we discuss complement, stimulation of inflammation, and immune evasion/suppression that leads to CoV-derived severe disease and mortality. The overall pathogenesis and disease progression of CoVs is put into perspective by indicating several stages in the resulting infection process in which both host and antiviral therapies could be targeted to block the viral cycle. Lastly, we discuss the development of adaptive immunity against various structural proteins, indicating specific vulnerable regions in the proteins. We discuss current CoV vaccine development approaches with purified proteins, attenuated viruses and DNA vaccines.

Design assessment of polymeric membranes modules to separate carbon dioxide from a binary mixture with methane

This work presents the performance assessment of diverse membrane arrangements to separate carbon dioxide (CO2) from a binary mixture with methane (CH4). For the purpose, we employ computer modeling to represent different polymeric modules, which are able to split an inlet CH4/CO2 gaseous mixture into sweet and acid products. Aim of the process is to achieve a high-purity CO2 permeate, reducing the CH4 losses. Novelty, we compare the performances of different existing commercial polymers, available for gas industries: cellulose acetate, polycarbonates, polyamides, polyamide-imides, polyamides thin-film composites, among others. The importance of the use of different materials is the possibility to replicate total membrane area, transport properties, and operating conditions. Finally, a comparative and integral discussion of the simulations considers three fundamental aspects: hydrocarbon recovery, residual gas quality, and compression power to carry out the separation.

Modification of rich-split carbon capture process using ceramic membrane for reducing the reboiler duty: Effect of membrane arrangements

In order to reduce the reboiler duty, the conventional CO2 chemical absorption process had been retrofitted by splitting some cold CO2-rich solvent prior to the lean-rich heat exchanger to recover the latent heat of hot stripped gas vented from CO2 desorber, which was called the rich-split carbon capture process. In this study, we promoted this rich-split carbon capture process by introducing 4 nm pore size tubular ceramic membranes, in which the coupled heat and water transfers from the stripped gas into the split CO2-rich monoethanolamine (MEA) aqueous solution across the membrane were permitted. Five types of ceramic membrane arrangements (Mode A to Mode E) were experimentally investigated and compared at different operating conditions in terms of the heat flux per volume of ceramic membrane (QCM). Results showed that among all the five ceramic membrane arrangements, the best heat recovery performance in terms of QCM value can be achieved using Mode-A where the stripped gas and rich MEA solvent flows were serially arranged in two serial ceramic membranes. Additionally, Mode-A has the best operating flexibility to the changes of water vapor content and stripped gas flow rate. Our study demonstrated that Mode-A may be an excellent candidate for recovering more waste heat at a high stripped gas flow rate. Furthermore, Mode-E can obtain a comparable heat recovery performance to Mode-A. In Mode-E, four parallel ceramic membrane tubes were bundled to form a heat exchanger with the same membrane volume to Mode-A. So if the layout of membrane tubes and shell size in Mode-E can be optimized elaborately, Mode-E will show a competitiveness in making the heat exchanger more compact on the premise of high heat recovery performance.

Estimation of concentration polarization in a fluidized bed reactor with Pd-based membranes via CFD approach

A fluidized bed membrane reactor has its great advantage in the industrial application of hydrogen production owing to good mass and heat transfer characteristics compared to a fixed bed membrane reactor. However, the concentration polarization and the densification zone formation caused by membrane permeation will restrict mass and heat transfer as well as hydrogen membrane flux. In this work, a three-dimensional simulation is carried out to investigate the hydrogen separation process in a fluidized bed membrane reactor under the Euler-Euler framework. The effects of membrane arrangements with different eccentric distances and membrane sites including internal and external membranes on concentration polarization and densification zones are discussed. The results reveal that the enhancement of eccentric distances can weaken the concentration polarization, whereas the densification zone scope is enhanced. The arrangement of internal membranes can hinder the concentration polarization and promote the hydrogen separation, while external membranes significantly influence the hydrogen removal at the bottom of the reactor.

Cubic membrane formation supports cell survival of amoeba Chaos under starvation-induced stress.

Cubic membranes (CM) are highly organized membrane structures found in biological systems. They are mathematically well defined and reveal a three-dimensional nano-periodic structure with cubic symmetry. These membrane arrangements are frequently induced in cells under stress, disease conditions, or upon viral infection. In this study, we investigated CM formation in the mitochondria of amoeba Chaos carolinense and observed a striking correlation between the organism's ability to generate CM and the cell survival under starvation. Since starvation also induces autophagy, rapamycin was used to pharmacologically induce autophagy, and interestingly, CM formation was observed in parallel. Conversely, inhibition of autophagy reverted the cubic mitochondrial inner membrane morphology to tubular structure. In starved Chaos cells, mitochondria and autophagosomes did not co-localize and ATP production was sustained. CM transition in the mitochondria during starvation or upon induction of autophagy might prevent their sequestration by autophagosomes, thus slowing their rate of degradation. Such sustained mitochondrial activity may allow amoeba Chaos cells to survive for a longer period upon starvation.

Evaluation of radical scavenging system in amoeba Chaos carolinense during nutrient deprivation.

The frequent appearance of non-lamellar membrane arrangements such as cubic membranes (CMs) in cells under stressed or pathological conditions points to an intrinsic cellular response mechanism. CM represents highly curved, three-dimensional nano-periodic structures that correspond to mathematically well-defined triply periodic minimal surfaces. Specifically, cellular membrane may transform into CM organization in response to pathological, inflammatory and oxidative stress conditions. CM organization, thus, may provide an advantage to cope with various types of stress. The identification of inducible membrane systems, such as in the mitochondrial inner membranes to cubic morphology upon starvation, opens new avenues for understanding the molecular mechanisms of cellular responses to oxidative stress. In this study, we compared the cellular responses of starved and fed amoeba Chaos carolinense to oxidative stress. Food deprivation from C. carolinense induces a significant increase in prooxidants such as superoxide and hydrogen peroxide. Surprisingly, we observed a significant lower rate of biomolecular damage in starved cells (with higher free radicals generation) when compared with fed cells. Specifically, lipid and RNA damages were significantly less in starved cells compared with fed cells. This observation was not due to the upregulation of intracellular antioxidants, as starved amoeba show reduced antioxidant enzymatic activities; however, it could be attributed to CM formation. CM could uptake and retain short segments of nucleic acids (resembles cellular RNA) in vivo and in vitro. Previous results showed that nucleic acids retained within CM sustain a minimal oxidative damage in vitro upon exposure to high level of superoxide. We thus propose that CM may act as a 'protective' shelter to minimize the oxidation of biologically essential macromolecules such as RNA. In summary, we examined enzymatic antioxidant activities as well as oxidative damage biomarkers in starved amoeba C. carolinense in correlation with the potential role of CM as an optimal intracellular membrane organization for the protection of biological macromolecules against oxidative damage.

(Invited) Graded Oxygen Transport Membranes for Energy Efficient Separation Applications

Oxygen transport membranes (OTM) have attracted great interest due to their ability to separate oxygen from air in an energy-efficient way. One major driver in the last decade was the potential CO2 sequestration, enabled by the Oxyfuel technology, i.e. combustion of fossil fuel with pure oxygen instead of air. Process simulations show that oxygen generation by ceramic membranes leads to significantly lower efficiency losses compared to conventional separation technologies. Another application of interest is the development of membrane reactors, combining the separation tasks with a chemical reaction, which is normally catalytically promoted. Such process intensification could play a significant role in future sustainable industrial production processes. Recently, a growing attention again is paid in petrochemical applications such as partial oxidation of methane to synthesis gas or oxidative coupling of methane to higher hydrocarbons such as ethylene, propylene, or even aromatics, which are important intermediates for the chemical industry. However, the demand on the materials stability in harsh operation conditions is much higher compared to the sole oxygen separation from air. OTMs are gastight Mixed Ionic Electronic Conductors (MIEC), which allow oxygen diffusion through oxygen vacancies and simultaneous conduction of electrons in the opposite direction. These processes require operation temperatures typically above 700°C. Obviously a key issue is the progress in the development of gastight oxygen separation membranes, which should have high oxygen permeation rates and at the same time sufficient thermal, chemical, and mechanical stability permitting a long term reliable operation. Since materials stability and permeability exhibit a trade-off a compromise has to be found. A promising approach is maximizing the oxygen permeation rate of stable materials by reducing the membrane thickness. However, a sole thickness reduction below a characteristic thickness Lc is not the solution as surface exchange kinetics becomes more and more rate limiting. The focus of the presentation lies on the development of materials and graded membrane arrangements for different applications. However, highly permeable membrane materials show a chemical instability against CO2, SOx and other flue gas components. One major challenge faced is therefore to identify and develop membrane materials, components, and a Proof of Concept-module for the 4-end mode OTM integration. The selected desired membrane assemblies will consist of a thin membrane layer supported on substrate with engineered porosity and oxygen reduction catalysts with high and stable activity in flue gas. The presentation is focussed on the material and microstructure aspect of stable perovskite and dual phase membranes. The manufacturing of thin supported membranes by sequential tape casing and the sintering procedure is shown and the characterisation of these membranes regarding performance (flux and conductivity), properties e.g. thermal and chemical expansion, stability and microstructure, etc. is shown.

Bio-Lithography: A Novel Process for Modification and Patterning of Supported Lipid Bilayers using Lipopolysaccharide, a Biological Amphiphile

Biological cell membranes are highly organized, multi-component systems that carry out complex energy and information processing. Supported lipid bilayers (SLBs) have shown great promise as model membranes but generating biologically-relevant complexity is challenging using existing membrane patterning techniques. Here we demonstrate an unconventional method that allows the controlled formation and in situ modification of complex membrane arrangements. Lipopolysaccharide (LPS) is a membrane-inserting amphiphile and an important human toxin. We recently reported that LPS can insert into and destabilize fluid-phase SLBs, leading to the formation of voids [Adams et al. (2014) Biophys J. 106, 2395]. We noted that the fluidity and continuity of the remainder of the SLB was maintained. In the current study, we exploit this effect of LPS to generate SLBs containing voids that can be backfilled to introduce desired functional components. This ‘biochemical-assisted lithography’ procedure was used to generate hierarchically organized membrane domains and microscale 2-D array patterns of domains. These domains could be formed using proteins, gel-phase lipids or even synthetic polymers. Alternatively, the voids could be healed by introducing new fluid-phase lipids. Significantly, this technique can be used to repeatedly modify membranes allowing iterative control over membrane composition. This approach expands our toolkit for functional membrane design, with potential applications for enhanced materials templating, biosensing and mimicking biological processes. Furthermore, we present fundamental insights into the interaction of lipids and other amphiphiles, demonstrating that line tension and alkyl chain packing effects can direct the organisation of a membrane-inserted amphiphile into geometric patterns.

NS4A and NS4B proteins from dengue virus: Membranotropic regions

Proteins NS4A and NS4B from Dengue Virus (DENV) are highly hydrophobic transmembrane proteins which are responsible, at least in part, for the membrane arrangements leading to the formation of the viral replication complex, essential for the viral life cycle. In this work we have identified the membranotropic regions of DENV NS4A and NS4B proteins by performing an exhaustive study of membrane rupture induced by NS4A and NS4B peptide libraries on simple and complex model membranes as well as their ability to modulate the phospholipid phase transitions Pβ′–Lα of DMPC and Lβ–Lα/Lα–HII of DEPE. Protein NS4A presents three membrane active regions coincident with putative transmembrane segments, whereas NS4B presented up to nine membrane active regions, four of them presumably putative transmembrane segments. These data recognize the existence of different membrane-active segments on these proteins and support their role in the formation of the replication complex and therefore directly implicated in the DENV life cycle.

A look through ‘lens’ cubic mitochondria

Cell membranes may fold up into three-dimensional nanoperiodic cubic structures in biological systems. Similar geometries are well studied in other disciplines such as mathematics, physics and polymer chemistry. The fundamental function of cubic membranes in biological systems has not been uncovered yet; however, their appearance in specialized cell types indicates a role as structural templates or perhaps direct physical entities with specialized biophysical properties. The mitochondria located at the inner segment of the retinal cones of tree shrew (Tupaia glis and Tupaia belangeri) contain unique patterns of concentric cristae with a highly ordered membrane arrangement in three dimensions similar to the photonic nanostructures observed in butterfly wing scales. Using a direct template matching method, we show that the inner mitochondrial membrane folds into multi-layered (8 to 12 layers) gyroid cubic membrane arrangements in the photoreceptor cells. Three-dimensional simulation data demonstrate that such multi-layer gyroid membrane arrangements in the retinal cones of a tree shrew's eye can potentially function as: (i) multi-focal lens; (ii) angle-independent interference filters to block UV light; and (iii) a waveguide photonic crystal. These theoretical results highlight for the first time the significance of multi-layer cubic membrane arrangements to achieve near-quasi-photonic crystal properties through the simple and reversible biological process of continuous membrane folding.

Optimum nanofi ltration membrane arrangements in seawater pretreatment - Part-I

NF membrane seawater pretreatment is an attractive technique that can provide unique permeate quality having negligible fouling and scaling potential and hence suitable for both membrane and thermal desalination processes. The technique was applied commercially in SWCC Umm-Lujj SWRO plant at 65% recovery. Operation at such recovery as pretreatment process is considered unattractive from the economic point of view. Accordingly, the aim of this study was to maximize NF product recovery and reduce operational cost while maintaining long membrane life. To achieve the target different investigation areas and techniques are considered. This paper presents Part-1 of this study which includes the performances of seven different NF arrangements in seawater pretreatment starting from 4 up to 20 NF elements in terms of recovery ratio, product quality, energy consumption and membrane hydraulic performance. The study revealed that 8-elements array at 65% recovery is the best choice for single stage NF process. Whereas...

A new recovery process of carbon dioxide from alkaline carbonate solution via electrodialysis

AbstractBipolar membrane electrodialysis is applied to CO2 recovery from alkaline carbonate solution. CO2 in flue gas is captured by an alkaline hydroxide absorbing solution to form an alkaline carbonate solution. The captured CO2 is recovered from the alkaline carbonate solution via bipolar membrane electrodialysis, and the alkaline solution is regenerated simultaneously. To reduce the power requirement for CO2 recovery, this study considers optimal design and operation. Three membrane arrangements were compared, and the results indicate the membrane arrangement comprising a bipolar membrane and cation exchange membrane is the most energy saving. With further optimization of operation conditions, the minimum power requirement for CO2 recovery was reduced to 2.1 MJ/kg‐CO2 (or 2.1 GJ/t‐CO2). © 2009 American Institute of Chemical Engineers AIChE J, 2009

Supramolecular organization of phycobiliproteins in the chlorophyll d-containing cyanobacterium Acaryochloris marina

Here we report the high-resolution detail of the organization of phycobiliprotein structures associated with photosynthetic membranes of the chlorophyll d-containing cyanobacterium Acaryochloris marina. Cryo-electron transmission-microscopy on native cell sections show extensive patches of near-crystalline phycobiliprotein rods that are associated with the stromal side of photosynthetic membranes. This supramolecular photosynthetic structure represents a novel mechanism of organizing the photosynthetic light-harvesting machinery. In addition, the specific location of phycobiliprotein patches suggests a physical separation of photosystem I and photosystem II reaction centres. Based on this finding and the known photosystem’s structure in Acaryochloris, we discuss possible membrane arrangements of photosynthetic membrane complexes in this species.

Pervaporation performance analysis and prediction—using a hybrid solution-diffusion and pore-flow model

A hybrid mathematic model for pervaporation is proposed which incorporates the concepts of solution-diffusion model and pore model. The model allows performance prediction as well as the establishment of the internal concentration and pressure profiles within the membrane. The model parameters specific to the particular membrane and mixture system are determined using liquid sorption and pervaporation experimental data. The model is experimentally examined using ethanol–water mixtures and poly(dimethyl siloxane)–poly(vinyldiene fluoride) (PDMS–PVDF) composite membranes. The characteristics of flux and separation factor predicted using the model are in fair agreement with the experimental data under various feed concentrations and downstream pressures for different membrane arrangements, including single-layer, reverse single-layer and double-layer PDMS–PVDF composite membranes. Internal profiles of pressure, concentration and component mole fraction can be established using the model. Concentration polarization phenomena for ethanol and water are located at membrane interfaces and vapor–liquid interfaces, respectively. Performances of several different membrane designs are compared using the model.

Asymmetric Bipolar Membranes in Acid−Base Electrodialysis

In this experimental study, the influence of asymmetric bipolar membranes on the salt impurities in the acid and base product is investigated. The thickness of one, the other, or both ion-permeable layers of a bipolar membrane is increased. With increased layer thickness, the current-voltage curves of the electrodialysis repeat unit recorded in a pilot-scale module show a reduced limiting current density, and thus they indicate an overall higher selectivity of these arrangements. Furthermore, these curves indicate water transport limitations for some membrane arrangements. Electrodialysis experiments with the same module at a high current density confirm the overall salt ion flux reduction. Moreover, these acid-base electrodialysis experiments directly reveal an increased asymmetry of the salt ion fluxes which can be utilized to design custom-made bipolar membranes with very high purity of either the produced acid or the base while keeping the bipolar membrane functioning without water transport limitations. The presented experiments also show that the bipolar membrane behavior can be characterized in situ, i.e., as a part of a electrodialysis repeat unit mounted in a pilot-scale electrodialysis module.