Membrane Properties Research Articles

Unravelling the effect of molecular interactions on macroscale properties in Sustainion anion exchange membrane (AEM) under hydrated conditions using MD simulations

Sustainion is an anion exchange water electrolyser membrane that has exhibited a scalable performance. In this work, we present a molecular model for the Sustainion membrane incorporating functionalization of the polymer in order to better mimic experimental conditions. Here in, we present a comprehensive exploration of its structural and transport properties like density, diffusivity and conductivity at various operating hydration levels using molecular dynamics simulations. The density exhibits a non-monotonic trend while the diffusivity showcases a non-linear behavior with hydration. Furthermore, diffusion exhibits an Arrhenius-like dependence on temperature with the activation energies exhibiting a non-monotonic relationship akin to the density. It is concluded that the afore-mentioned properties of the Sustainion membrane are due to the counteracting influence of the enhancement in coordination number, and a reduction in the potentials of mean force of the different atomic pairs in the system. The effect of added salt on Sustainion properties is also determined and collated with experiments. Based on comparison with experiment, we deduce that vehicular diffusion is the predominant mechanism in the diffusion of the chloride ion, while it contributes approximately 15% to the diffusivity of the hydroxide ion.

Thermally stabilized polyacrylonitrile/polyphenylene sulfide composite membranes for efficient emission control in harsh environments

In harsh and complex environments, the emission of polluted air poses significant challenges to traditional filtration systems. In contrast to conventional approaches which primarily involve the incorporation of antioxidants into filter materials, this study introduces a novel methodology. Here, we employed polyacrylonitrile (PAN) as a coating for polyphenylene sulfide (PPS) fibers. Furthermore, we innovatively utilized a needle punching process in conjunction with segmented heat treatment to manufacture PAN-PPS composite filter membranes capable of withstanding extreme environmental conditions. During the segmented heat treatment process, the molecular structure of PAN coating underwent a series of changes, ultimately transforming into a heat-resistant ring trapezoidal structure, providing protection for PPS fibers that are prone to oxidation, and thereby enhancing the structural stability of composite filter membrane. Experimental results demonstrated a significant improvement in the mechanical properties of PAN-PPS composite fabric after segmented heat treatment, with the tensile strength increasing by 71.7 % and the Young’s modulus by 91.6 %. Additionally, the flame retardancy and hydrophobic properties of composite membranes were significantly enhanced, exhibiting the excellent stability and better filtration performance in extreme environments. This approach not only addresses the challenges posed by incorporating nano antioxidants into the spinning process but also significantly enhances the high-temperature resistance of the materials. This enables PAN-PPS composite filter bags to effectively control the emission of polluted gases in extreme environments. Furthermore, the thermal treatment process of the PAN coating is easy to implement and cost-effective, providing a novel strategy for the development of extremely high-temperature resistant filtering materials. This makes it possible to explore the development of flexible, high-performance air filtering materials for extreme environments in the future.

Highly durable perfluorosulfonic acid proton exchange membrane by combining inorganic free radical scavengers and organic antioxidants

In this work, a new type of complex was constructed by coordinating quercetin (QC) with cerium (Ce) ions. This complex was introduced into perfluorosulfonic acid resin (PFSA) to fabricate a proton exchange membrane. The coordination process prevented the formation of ion cross-links between cerium and sulfonic acid groups in PFSA, thereby keeping proton conductivity and fuel cell performance of membrane samples at a high level. Due to the insolubility of quercetin in water, its coordination with cerium minimized cerium migration, providing long-lasting resistance to free radicals. The effects of additives on PFSA membrane properties were investigated by measuring IEC, water uptake, swelling ratio, and proton conductivity. Fenton degradation experiments and membrane electrode assembly performance tests was conducted simultaneously. The results demonstrated that compared to the addition of quercetin or cerium alone, the use of QC-Ce increased the proton conductivity by 23.70% after 24-h Fenton degradation and lowered fluoride release by 58.29%. Meanwhile, the PFSA/QC-Ce composite membrane samples maintained an open circuit voltage of 0.935 V and a maximum power density of 668.15 mW cm−2 after 96 h of open circuit voltage hold testing.

Elastic Properties of Low-Dimensional Single-Crystalline Dielectric Oxides through Controlled Large-Area Wrinkle Generation.

Freestanding single-crystalline SrTiO3 membranes, as high-κ dielectrics, hold significant promise as the gate dielectric in two-dimensional (2D) flexible electronics. Nevertheless, the mechanical properties of the SrTiO3 membranes, such as elasticity, remain a critical piece of the puzzle to adequately address the viability of their applications in flexible devices. Here, we report statistical analysis on plane-strain effective Young's modulus of large-area SrTiO3 membranes (5 × 5 mm2) over a series of thicknesses (from 6.5 to 32.2 nm), taking advantage of a highly efficient buckling-based method, which reveals its evident thickness-dependent behavior ranging from 46.01 to 227.17 GPa. Based on microscopic and theoretical results, we elucidate these thickness-dependent behaviors and statistical data deviation with a bilayer model, which consists of a surface layer and a bulk-like layer. The analytical results show that the ∼3.1 nm surface layer has a significant elastic softening compared to the bulk-like layer, while the extracted modulus of the bulk-like layer shows a variation of ∼40 GPa. This variation is considered as a combined contribution from oxygen deficiency presenting in SrTiO3 membranes, and the alignment between applied strain and the crystal orientation. Upon comparison of the extracted elastic properties and electrostatic control capability to those of other typical gate dielectrics, the superior performance of single-crystalline SrTiO3 membranes has been revealed in the context of flexible gate dielectrics, indicating the significant potential of their application in high-performance flexible 2D electronics.

Preparation and properties of asymmetric inverse opal-like microfiltration membranes

Most types of commercially available MF membranes suffer limited separation performances due to huge deviations in pore size and low porosity. In view of this, a new and facile assembly strategy was proposed to prepare an asymmetric inverse opal (IO) like microfiltration (MF) membrane with ordered pore structure, high porosity and large water flux, which is a composite of a disordered layer with three-dimensional pore structures made by dissolved N, N-dimethylformamide (DMF) and an ordered layer with uniform pore size by using a sacrificial template method. The effects of SiO2 microsphere size and DMF treatment on the structure and properties have been investigated. Different DMF treatment times can significantly change the asymmetric structure distribution of MF membrane and further affect the permeability. The water flux of the asymmetric membrane increases with the DMF infiltration time. Based on the SiO2 microsphere template size of 494 nm and the DMF treatment time of 90 s, the porosity and pure water flux can reach 78 % and 1810 L/m2h, respectively. The membrane retains the IO-like structure layer with uniform pore size, and features excellent retention (almost 100 %) for SiO2 microspheres, indicating the great potential of asymmetric IO-like MF membranes for membrane separation applications.

GluN2A or GluN2B subunits of the NMDA receptor contribute to changes in neuronal excitability and impairments in LTP in the hippocampus of aging mice but do not mediate detrimental effects of oligomeric Aβ (1–42)

Studies in rodent models have revealed that oligomeric beta-amyloid protein [Aβ (1–42)] plays an important role in the pathogenesis of Alzheimer’s disease. Early elevations in hippocampal neuronal excitability caused by Aβ (1–42) have been proposed to be mediated via enhanced activation of GluN2B-containing N-methyl-D-aspartate receptors (NMDAR). To what extent GluN2A or GluN2B-containing NMDAR contribute to Aβ (1–42)-mediated impairments of hippocampal function in advanced rodent age is unclear. Here, we assessed hippocampal long-term potentiation (LTP) and neuronal responses 4–5 weeks after bilateral intracerebral inoculation of 8–15 month old GluN2A+/− or GluN2B+/− transgenic mice with oligomeric Aβ (1–42), or control peptide. Whole-cell patch-clamp recordings in CA1 pyramidal neurons revealed a more positive resting membrane potential and increased total spike time in GluN2A+/−, but not GluN2B+/−-hippocampi following treatment with Aβ (1–42) compared to controls. Action potential 20%-width was increased, and the descending slope was reduced, in Aβ–treated GluN2A+/−, but not GluN2B+/− hippocampi. Sag ratio was increased in Aβ–treated GluN2B+/−-mice. Firing frequency was unchanged in wt, GluN2A+/−, and GluN2B+/−hippocampi after Aβ–treatment. Effects were not significantly different from responses detected under the same conditions in wt littermates, however. LTP that lasted for over 2 h in wt hippocampal slices was significantly reduced in GluN2A+/− and was impaired for 15 min in GluN2B+/−-hippocampi compared to wt littermates. Furthermore, LTP (>2 h) was significantly impaired in Aβ–treated hippocampi of wt littermates compared to wt treated with control peptide. LTP induced in Aβ–treated GluN2A+/− and GluN2B+/−-hippocampi was equivalent to LTP in control peptide-treated transgenic and Aβ–treated wt animals. Taken together, our data indicate that knockdown of GluN2A subunits subtly alters membrane properties of hippocampal neurons and reduces the magnitude of LTP. GluN2B knockdown reduces the early phase of LTP but leaves later phases intact. Aβ (1–42)-treatment slightly exacerbates changes in action potential properties in GluN2A+/−-mice. However, the vulnerability of the aging hippocampus to Aβ–mediated impairments of LTP is not mediated by GluN2A or GluN2B-containing NMDAR.

Fabrication of Hydrophobic PET Track-Etched Membranes using 2,2,3,3,4,4,4-Heptafluorobutyl Methacrylate for Water Desalination by Membrane Distillation

The world is currently facing a drinking water problem. Human activity, climate change and pollution of existing water bodies are exacerbating the problem. The scientists around the world are currently trying to purify water using effective and inexpensive methods. One such method is membrane distillation. Membrane distillation is a versatile thermally driven membrane separation process. This method of water purification has the potential to remove salts and other non-volatile components. The work is concerned with the desalination of salt solutions by membrane distillation using ion-track membranes based on polyethylene terephthalate (PET). PET ion-track membranes (PET TMs) were modified by photoinitiated graft polymerization of 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (HFBMA) to make them hydrophobic. Optimal polymerization conditions (monomer concentration, reaction time) were determined, which led to an increase of water CA from 51 to 105°. The obtained membranes were used to purify the solution from NaCl. The effect of salt concentration as well as membrane properties on performance and degree of purification was studied. The results show that large pore size PET TMs modified with HFBMA has the potential to desalinate water in an efficient manner.

Droplet Polymer Bilayers for Bioelectronic Membrane Interfacing.

Model membranes interfaced with bioelectronics allow for the exploration of fundamental cell processes and the design of biomimetic sensors. Organic conducting polymers are an attractive surface on which to study the electrical properties of membranes because of their low impedance, high biocompatibility, and hygroscopic nature. However, establishing supported lipid bilayers (SLBs) on conducting polymers has lagged significantly behind other substrate materials, namely, for challenges in membrane electrical sealing and stability. Unlike SLBs that are highly dependent on surface interactions, droplet interface bilayers (DIBs) and droplet hydrogel bilayers (DHBs) leverage the energetically favorable organization of phospholipids at atomically smooth liquid interfaces to build high-integrity membranes. For the first time, we report the formation of droplet polymer bilayers (DPBs) between a lipid-coated aqueous droplet and the high-performing conducting polymer poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS). The resulting bilayers can be produced from a range of lipid compositions and demonstrate strong electrical sealing that outcompetes SLBs. DPBs are subsequently translated to patterned and planar microelectrode arrays to ease barriers to implementation and improve the reliability of membrane formation. This platform enables more reproducible and robust membranes on conducting polymers to further the mission of merging bioelectronics and synthetic, natural, or hybrid bilayer membranes.

Pressure Changes Across a Membrane Formed by Coacervation of Oppositely Charged Polymer-Surfactant Systems.

We investigate the mass transfer and membrane growth processes during capsule formation by the interaction of the biopolymer xanthan gum with CnTAB surfactants. When a drop of xanthan gum polymer solution is added to the surfactant solution, a membrane is formed by coacervation. It encapsulates the polymer drop in the surfactant solution. The underlying mechanisms and dynamic processes during capsule formation are not yet understood in detail. Therefore, we characterized the polymer-surfactant complex formation during coacervation by measuring the surface tension and surface elasticity at the solution-air interface for different surfactant chain lengths and concentrations. The adsorption behavior of the mixed polymer-surfactant system at the solution-air interface supports the understanding of observed trends during the capsule formation. We further measured the change in capsule pressure over time and simultaneously imaged the membrane growth via confocal microscopy. The cross-linking and shrinkage during the membrane formation by coacervation leads to an increasing tensile stress in the elastic membrane, resulting in a rapid pressure rise. Afterward, the pressure gradually decreases and the capsule shrinks as water diffuses out. This is not only due to the initial capsule overpressure but also due to osmosis caused by the higher ionic strength of the surfactant solution outside the capsule compared to the polymer solution inside the capsule. The influence of polymer concentration and surfactant type and concentration on the pressure changes and the membrane structure are studied in this work, providing detailed insights into the dynamic membrane formation process by coacervation. This knowledge can be used to produce capsules with tailored membrane properties and to develop a suitable encapsulation protocol in technological applications. The obtained insights into the mass transfer of water across the capsule membrane are important for future usage in separation techniques and the food industry and allow us to better predict the capsule time stability.

Self-Assembled Hydrogel Membranes with Structurally Tunable Mechanical and Biological Properties.

Using supramolecular self-assembled nanocomposite materials made from protein and polysaccharide components is becoming more popular because of their unique properties, such as biodegradability, hierarchical structures, and tunable multifunctionality. However, the fabrication of these materials in a reproducible way remains a challenge. This study presents a new evaporation-induced self-assembly method producing layered hydrogel membranes (LHMs) using tropocollagen grafted by partially deacetylated chitin nanocrystals (CO-g-ChNCs). ChNCs help stabilize tropocollagen's helical conformation and fibrillar structure by forming a hierarchical microstructure through chemical and physical interactions. The LHMs show improved mechanical properties, cytocompatibility, and the ability to control drug release using octenidine dihydrochloride (OCT) as a drug model. Because of the high synergetic performance between CO and ChNCs, the modulus, strength, and toughness increased significantly compared to native CO. The biocompatibility of LHM was tested using the normal human dermal fibroblast (NHDF) and the human osteosarcoma cell line (Saos-2). Cytocompatibility and cell adhesion improved with the introduction of ChNCs. The extracted ChNCs are used as a reinforcing nanofiller to enhance the performance properties of tropocollagen hydrogel membranes and provide new insights into the design of novel LHMs that could be used for various medical applications, such as control of drug release in the skin and bone tissue regeneration.

Preparation and performance study of waste plastic blended ultrafiltration membrane

Waste plastic packaging bags (rPVC) and waste milk tea straws (rPLA) were used as membrane materials to prepare ultrafiltration (UF) membranes by the non-solvent induced phase separation (NIPS) method. The study aimed to investigate the influence of various factors, including different rPVC contents (10 wt%-20 wt%), membrane fractions (rPVC/rPLA), additive fractions (Pluronic F-127/PVP-K30), and different additive contents (0.5 wt%-3.0 wt%), on the performance of the membranes. The permeability, morphology, hydrophilicity, chemical composition, thermal stability, and antifouling properties of the blended UF membranes were thoroughly investigated. The experimental results revealed that the presence of rPLA and Pluronic F-127 increased the porosity, water absorption, pore size, and hydrophilicity of the blended UF membranes. Furthermore, the introduction of rPLA enhanced the thermal stability of the blended UF membranes. Additionally, the incorporation of Pluronic F-127 further improved the overall performance of the blended UF membranes. Specifically, it was found that the blended UF membranes achieved a pure water flux (PWF) of 192.50 L·m−2·h−1, while maintaining a bovine serum albumin (BSA) rejection rate of 95.20%. These results were obtained using a content ratio of rPVC/rPLA (90/10) at 14 wt% and an additive content of Pluronic F-127 at 2.5 wt%. By comparing with the blended UF membranes without introducing additives into the casting solution, the roughness (Ra) was reduced by 40.3%, the water contact angle (WCA) was reduced by 7.5%, the flux recovery rate (FRR) was increased by 80.5%, and the fouling resistance was enhanced.

Microstructure and performance modification of PVDF ultrafiltration membrane via adjusting the composition of coagulation Bath

AbstractIn this paper, the effect of the composition of a nonsolvent bath on the physicochemical properties of the polyvinylidene fluoride (PVDF) ultrafiltration membranes were comprehensively investigated using the nonsolvent‐induced phase separation method. Three additives (ethanol, glycerol, or NaCl) were added to the water coagulation bath respectively to obtain different membranes. It was found that the microstructure of the membranes changed from finger‐like structure to the sponge‐like structure with the increase of additives concentration, which successfully improved the retention and mechanical properties of the membranes. In addition, the membrane surface became smoother and more hydrophilic. The membrane fabricated in 30 wt% glycerol bath exhibited outstanding comprehensive properties of retention and anti‐fouling, with a water flux of 243.5 L/(m2 h), a bovine serum albumin rejection of more than 90%, and a flux recovery rate of 97%. From mechanism analysis, the addition of ethanol, glycerol, or NaCl to the coagulation bath altered the thermodynamic stability of the polymer system, and slowed down the rate of solvent and nonsolvent diffusion from a kinetic perspective. This research provides important clues for optimizing the membrane properties, such as flux, rejection, and strength.

Multifaceted Activity of Fabimycin: Insights from Molecular Dynamics Studies on Bacterial Membrane Models.

Membranes─cells' essential scaffolds─are valid molecular targets for substances with an antimicrobial effect. While certain substances, such as octenidine, have been developed to target membranes for antimicrobial purposes, the recently reported molecule, fabimycin (F2B)─a novel agent targeting drug-resistant Gram-negative bacteria─has not received adequate attention regarding its activity on membranes in the literature. The following study aims to investigate the effects of F2B on different bacterial membrane models, including simple planar bilayers and more complex bilayer systems that mimic the Escherichia coli shell equipped with double inner and outer bilayers. Our results show that F2B exhibited more pronounced interactions with bacterial membrane systems compared to the control PC system. Furthermore, we observed significant changes in local membrane property homeostasis in both the inner and outer membrane models, specifically in the case of lateral diffusion, membrane thickness, and membrane resilience (compressibility, tilt). Finally, our results showed that the effect of F2B differed in a complex system and a single membrane system. Our study provides new insights into the multifaceted activity of F2B, demonstrating its potential to disrupt bacterial membrane homeostasis, indicating that its activity extends the currently known mechanism of FabI enzyme inhibition. This disruption, coupled with the ability of F2B to penetrate the outer membrane layers, sheds new light on the behavior of this antimicrobial molecule. This highlights the importance of the interaction with the membrane, crucial in combating bacterial infections, particularly those caused by drug-resistant strains.

Cellular uptake of active nonspherical nanoparticles

Due to the potential applications in biomedical engineering, it becomes more and more important to understand the process of engulfment and internalization of nanoparticles (NPs) by cell membranes. Despite the fact that the interaction between cell membranes and passive particles has been widely studied, the interaction between cell membranes and self-propelled nonspherical NPs remains to be elucidated. Here, we present a theoretical model to systematically investigate the influence of the active force, aspect ratio of NPs, particle size, and membrane properties (adhesion energy density and membrane tension) on the cellular uptake of a nonspherical nanoparticle. It is found that the active force generated by an NP can trigger a type of first-order wrapping transition from a small partial wrapping state to a large one. In addition, the phase diagram in the force-aspect ratio (particle size, adhesion energy density, and membrane tension) space displays more complex behaviors compared with that for the passive wrapping mediated merely by adhesion. These results may provide useful guidance to the study of activity-driven cellular entry of active particles into cells.

The characteristics of high temperature polymer electrolyte membranes for fuel cell based on 2-pyridene based polybenzimidazole blended with poly(vinyl-phosphonic acid)

The present study has focused on exploring new 2-pyridine-bridge-based polybenzimidazole (2-Py-PBIs) based materials for various energy-related uses in proton exchange membrane fuel cells (PEMFC). An electrochemical device, which transforms chemical energy into electrical energy, is known as fuel cell. Using solution polymerization with polyphosphoric acid as a solvent, a series of 2-Py-PBIs were synthesised from the 4,4'-([2,4′-bipyridine]-2′,6′-diyl)bis (benzene-1,2-diamine). 2-Pyridine bridge Polybenzimidazoles are cross-linked with poly (vinylphosphonic acid), which helps us to improve membrane properties like mechanical properties and proton conductivities. FT-IR was used to characterize chemical structure, Ubbelohde viscometer was employed to determine the inherent viscosity. Additionally investigated were the oxidative stability, swelling ratio, ion exchange capability, and water uptake for 2-Py-PBIs. Thermogravimetric analysis is used to evaluate thermal stability. The obtained 2-Py-PBIs membranes were thermally stable and mechanically strong when compared with conventional polybenzimidazole-based membranes. The 2-Py-PBIs:PVPA membranes showed proton conductivity between 0.10 µS/m to 4.65 µS/m.

Driving Role of Zinc Oxide Nanoparticles with Different Sizes and Hydrophobicity in Metabolic Response and Eco-Corona Formation in Sprouts (Vigna radiata).

Zinc oxide nanoparticles (ZnO NPs) cause biotoxicity and pose a potential ecological threat; however, their effects on plant metabolism and eco-corona evolution between NPs and organisms remain unclear. This study clarified the molecular mechanisms underlying physiological and metabolic responses induced by three different ZnO NPs with different sizes and hydrophobicity in sprouts (Vigna radiata) and explored the critical regulation of eco-corona formation in root-nano systems. Results indicated that smaller-sized ZnO inhibited root elongation by up to 37.14% and triggered oxidative burst and apoptosis. Metabolomics confirmed that physiological maintenance after n-ZnO exposure was mainly attributed to the effective stabilization of nitrogen fixation and defense systems by biotransformation of the flavonoid pathway. Larger-sized or hydrophobic group-modified ZnO exhibited low toxicity in sprouts, with 0.89-fold upregulation of citrate in central carbon metabolism. This contributed to providing energy for resistance to NP stress through amino acid and carbon/nitrogen metabolism, accompanied by changes in membrane properties. Notably, smaller-sized and hydrophobic NPs intensely stimulated the release of root metabolites, forming corona complexes with exudates. The hydrogen-bonded wrapping mechanism in protein secondary structure and hydrophobic interactions of heterogeneous functional groups drove eco-corona formation, along with the corona evolution intensity of n-ZnO > s-ZnO > b-ZnO based on higher (α-helix + 3-turn helix)/β-sheet ratios. This study provides crucial insight into metabolic and eco-corona evolution in bionano fates.

Integration of proton exchange membrane fuel cell with air gap membrane distillation for sustainable electricity and freshwater cogeneration: Performance, influential mechanism, multi-objective optimization and future perspective

Proton exchange membrane fuel cell (PEMFC) converts vast majority of hydrogen energy into waste heat, resulting in energy wasting, membrane drying and even lifetime shortening. Herein, air gap membrane distillation is proposed to immediately remove and harness the waste heat from PEMFC for additional freshwater production. By quantifying the irreversible thermodynamic and electrochemical losses, mathematical formulas for the water production, power generation and overall efficiency are derived to evaluate the system performance. After a rigorous model validation, the performance feature, feasibility and competitiveness of the proposed system are examined. The integration system achieves a peak power density 23.69 % higher than that of a single PEMFC at 353 K, with a corresponding increase in exergy efficiency by 3.61 %. In addition, the influential mechanisms of the PEMFC operating conditions, air gap thickness, coolant temperature, and properties of the proton exchange membrane and hydrophobic porous membrane are investigated to discern potential avenues for further performance improvement. The gradient-based local sensitivity analyses further determine the optimal parameter regulation strategies for different output targets. The economic study indicates that the levelized costs of water and electricity over the total lifecycle are 21.53 $ m−3 and 0.061 $ kWh−1, respectively. The multi-objective optimization, integrating genetic algorithm and the technique for order preference by similarity to an ideal solution, maximizes the exergy efficiency and output power density while minimizing the initial investment cost per unit area, with values of 42.84 %, 0.975 W cm−2, and 27.33 $ cm−2, respectively.

Estimation of mixed-gas selectivity of membranes using the linear friction-based model

The development of analytical models for predicting the transport properties of membranes in the separation of multicomponent mixtures is highly relevant because (1) measurements of permeability and sorption of gas mixtures in membrane materials are laborious and time-consuming, and (2) estimation of transport properties based on pure gas measurements is desirable, however, rather unreliable and can lead to serious errors. In this paper, within the framework of the well-known frictional-coefficient formalism, we present nonlinear equations for the fluxes of gas mixture components through the membrane, which take into account the diffusional coupling of the fluxes compared to independent gas transport. As a result, an analytical equation for the mixed-gas selectivity was obtained. This equation has an implicit form, which is not quite convenient for practical application, since it has to be solved numerically. A simple explicit expression for mixed gas selectivity was derived using the so-called linear transport model, which is a linearized version of the original nonlinear flux equations. It is important to emphasize that a comparison of the linear model with the formally more rigorous nonlinear model showed only minor quantitative differences. The input parameters for the model are the single gas transport parameters. Testing the linear model using experimental data for the separation of hydrocarbons (n-butane/methane, n-butane/i-butane, propylene/propane) revealed an acceptable fit. A comparison of the model with recent experimental data on the separation of CO2-containing mixtures using microporous polymers is also presented. It is found that the calculated CO2/N2 mixed gas selectivity is in good agreement with the experimental data, while only a semi-quantitative agreement is observed for the CO2/CH4 separation. Besides, it is shown that the model developed for binary gas separation can be extended to ternary gas mixtures.

Interactions of Brominated Flame Retardants with Membrane Models of Dehalogenating Bacteria: Langmuir Monolayer and Grazing Incidence X-ray Diffraction Studies.

Brominated flame retardants (BFRs) are small organic molecules containing several bromine substituents added to plastics to limit their flammability. BFRs can constitute up to 30% of the weight of some plastics, which is why they are produced in large quantities. Along with plastic waste and microplastic particles, BFRs end up in the soil and can easily leach causing contamination. As polyhalogenated molecules, multiple BFRs were classified as persistent organic pollutants (POPs), meaning that their biodegradation in the soils is especially challenging. However, some anaerobic bacteria as Dehaloccocoides can dehalogenate BFRs, which is important in the bioremediation of contaminated soils. BFRs are hydrophobic, can accumulate in plasma membranes, and disturb their function. On the other hand, limited membrane accumulation is necessary for BFR dehalogenation. To study the BFR-membrane interaction, we created membrane models of soil dehalogenating bacteria and tested their interactions with seven legacy and novel BFRs most common in soils. Phospholipid Langmuir monolayers with appropriate composition were used as membrane models. These membranes were doped in the selected BFRs, and the incorporation of BFR molecules into the phospholipid matrix and also the effects of BFR presence on membrane physical properties and morphology were studied. It turned out that the seven BFRs differed significantly in their membrane affinity. For some, the incorporation was very limited, and others incorporated effectively and could affect membrane properties, while one of the tested molecules induced the formation of bilayer domains in the membranes. Thus, Langmuir monolayers can be effectively used for pretesting BFR membrane activity.

Effects of cell configuration and bipolar membrane on preparation of LiOH through bipolar membrane electrodialysis from salt lake brine

Bipolar membrane electrodialysis (BMED) is a promising process to prepare LiOH from the salt lake brine. Revealing the effects of the cell configuration and property of bipolar membrane (BM) on the mass transfer and current efficiency of BMED is crucial to promote its industrial application. Herein, two-compartment (C-B) and three-compartment (A-C-B), and three types of BMs (FBM, BP-1, and TWBP1) were systematically studied. Results show that three-compartment is superior to two-compartment, as the latter could restrain electromigration of Li+, enable recombination of H+ and OH–, and lead to lower current efficiency. Among three BMs, TWBP1 has highest current efficiency, while BP-1 can prepare LiOH solution with least impurity ions. To reveal the influencing mechanism of the BMs’ properties on the electromigration of Li+ and co-ions leakage, CVC curves and chronopotentiograms were detailly investigated. Results show that the higher energy consumption of BP-1 may be attributed to its highest specific resistivity, while its better co-ions selectivity is beneficial to prepare acid/base solutions with lesser impurities, indicating that effects of the specific resistivity and selectivity of BMs on BMED process for producing LiOH from salt lake brine is an important “trade-off” relationship needing to be balanced to realize the higher current efficiency and higher quality products.