Capacity Of Membranes Research Articles

Synthesis and Characterization of Ceramide-Containing Liposomes as Membrane Models for Different T Cell Subpopulations

A fine balance of regulatory (Treg) and conventional CD4+ T cells (Tconv) is required to prevent harmful immune responses, while at the same time ensuring the development of protective immunity against pathogens. As for many cellular processes, sphingolipid metabolism also crucially modulates the Treg/Tconv balance. However, our understanding of how sphingolipid metabolism is involved in T cell biology is still evolving and a better characterization of the tools at hand is required to advance the field. Therefore, we established a reductionist liposomal membrane model system to imitate the plasma membrane of mouse Treg and Tconv with regards to their ceramide content. We found that the capacity of membranes to incorporate externally added azide-functionalized ceramide positively correlated with the ceramide content of the liposomes. Moreover, we studied the impact of the different liposomal preparations on primary mouse splenocytes in vitro. The addition of liposomes to resting, but not activated, splenocytes maintained viability with liposomes containing high amounts of C16-ceramide being most efficient. Our data thus suggest that differences in ceramide post-incorporation into Treg and Tconv reflect differences in the ceramide content of cellular membranes.

On the Characterization of Membrane Transport Phenomena and Ion Exchange Capacity for Non-Aqueous Redox Flow Batteries

The development of high-performance membrane materials for non-aqueous redox flow batteries (NAqRFBs) could unlock a milestone towards widespread commercialization of the technology. Understanding of transport phenomena through membrane materials requires diagnostic tools able to monitor the concentrations of redox active species. While membrane characterization in aqueous media focused the attention of the scientific community, dedicated efforts for non-aqueous electrolytes remain poorly developed. Here, we develop new methodologies to assess critical membrane properties, namely ion exchange capacity and species transport, applied to NAqRFBs. In the first part, we introduce a method based on 19F-NMR to quantify ion exchange capacity of membranes with hydrophobic anions commonly used in non-aqueous systems (e.g., PF6 − and BF4 −). We find a partial utilization of the ion exchange capacity compared to the values reported using traditional aqueous chemistry ions, possibly limiting the performance of NAqRFB systems. In the second part, we study mass transport with a microelectrode placed on the electrolyte tank. We determine TEMPO crossover rates through membranes by using simple calibration curves that relate steady-state currents at the microelectrode with redox active species concentration. Finally, we show the limitations of this approach in concentrated electrolyte systems, which are more representative of industrial flow battery operation.

A novel lithium ion-imprinted membrane with robust adsorption capacity and anti-fouling property based on the uniform multilayered interlayer

Effective modification strategies contribute to high adsorption capacity, separation efficiency and anti-fouling properties of ion-imprinted membranes. The design of a homogeneous and hydrophilic interlayer between the substrate membrane and ion-imprinted layer is crucial factor for the excellent performance of ion-imprinted membranes. In this study, a novel multilayered interlayer (SiO2@SP-PDA) was developed and uniformly coated on the substrate surface (PVDF membrane). The polydopamine (PDA) prepared via oxidation of sodium periodate (SP-PDA) increases the uniformity of SiO2@SP-PDA modification, which reduces the agglomeration of the ion-imprinted layer, and thereby boosts the adsorption capacity to 231.77 mg·g−1. The prepared ion-imprinted membrane (SiO2@SP-PDA-IIM) exhibits a favorable anti-fouling property due to the incremental hydrophilicity and the presence of SiO2 nano interlayer. Based on the XDLVO theory, it can be deduced that the SiO2 modification increases the membrane surface electron donor tension (γ−), which plays an essential role in enhancing the anti-fouling property of SiO2@SP-PDA-IIM. In this paper, the design of multilayered structure is of great significance to make the ion-imprinted membrane be a potential candidate for Li+ efficient separation in natural water.

Montmorillonite-perlite-iron ceramic membranes for the adsorption/removal of As(III) and other constituents from surface water

In this study, ceramic membranes made of montmorillonite, perlite and iron were used to remove As(III) from water. Membranes prepared with 0.0, 0.5, 1.0, and 1.5 wt% of iron content were used to filtrate As(III) synthetic water and surface water solutions. As(III) adsorption capacity and removal efficiency, and other parameters such as cations and anions content, turbidity, pH, electrical conductivity were used to evaluate the membranes' performance. Results show that the As(III) adsorption/removal capacity of membranes was improved by the addition of iron. Adsorption capacity of 7.5 μg As(III)/g and removal efficiency of 97% can be achieved in membranes with 1.0 wt% of iron filings content for surface water; however, a greater amount of iron in the membrane structure limits the adsorption capacity of As(III). Besides the capacity of ceramic membranes to adsorb/remove As(III), membranes were also effective to remove other ions, turbidity, and electrical conductivity from the surface water. The addition of iron to the ceramic membranes enhanced their capacity to remove such surface water constituents. These results are important from the practical viewpoint showing the potential of ceramic membranes for the removal of metalloids and other water constituents. Langmuir isotherm model best described the adsorption process in ceramic membranes, suggesting that adsorption of As(III) happened on a monolayered surface of the ceramic membrane.

Magnolol-derived thiol-ene photo-polymerized membranes with intrinsic anti-flammability and high transparency

In this study, a phosphorus-containing bio-based monomer (MBDPP) was first synthesized from renewable magnolol, and subsequently photo-cured with tri-thiol (TPTMP) or tetra-thiol (PETMP) monomers via thiol–ene polymerization. The synthesized MBDPP/TPTMP and MBDPP/PETMP membranes exhibited high char residues at 700 °C in the TGA tests, which were 19.8 wt% and 24.2 wt% for nitrogen while 16.5 wt% and 20.2 wt% for air, respectively, indicating superior charring capacity of both membranes. DMA results indicated that both the higher stiffness and the Tg of the cured MBDPP/PETMP membrane was ascribed to its higher cross-linking density than that of the cured MBDPP/TPTMP owing to the tetra-functional groups of PETMP. In the open flame test, both MBDPP/TPTMP and MBDPP/PETMP membranes self-extinguished immediately when removing the flame source, manifesting excellent intrinsic anti-flammability. The cone calorimeter results further demonstrated that MBDPP/TPTMP and MBDPP/PETMP membranes showed lower PHRR (419 and 388 kW/m2, respectively) and THR (41.38 and 38.98 MJ/m2, respectively) values than most of the thiol-ene photo-polymerized counterparts previously reported. The excellent anti-flammability of MBDPP/TPTMP and MBDPP/PETMP membranes originated from the formation of expandable char residues that played an efficient role in hampering the transfer of flammable pyrolysis products to flame zone as well as insulating the heat irradiation during combustion. Additionally, both MBDPP/TPTMP and MBDPP/PETMP membranes showed excellent transparency (transmittance >85% in the visible region) and flexibility (breaking elongation around 40%). Taking the intrinsic anti-flammability, exceptional transparency and high flexibility into account, the MBDPP/TPTMP and MBDPP/PETMP systems are suitable as intumescent flame retardant coating materials.

Evaluation of properties and performance of poly(ether sulfone ketone) membranes in proton exchange membrane fuel cells

AbstractTwo series of sulfonated poly(ether sulfone ketone)s have been synthesized. The effect of different ratios of sulfone: ketone functional groups on the properties and performance of membranes is studied. The density, ion‐exchange capacity, water absorption, swelling ratio, proton conductivity, thermal and oxidative stability of membranes are determined. The results showed that membranes with higher contents of sulfone functional groups show lower density and consequently higher water absorption and swelling ratio values. A precise evaluation of the effect of different sulfone: ketone functional group ratios on the analytical acid concentration and the effective proton mobility and their relationship with water absorption have been performed. The proton conductivity values are between 71–78 mS.cm−1 at 30°C and 117–208 mS.cm−1 at 80°C. The effective proton mobilities at 80°C are in the range of 10.27 × 10 −4 to 16.68 × 10 −4 cm2.V−1.s−1. The highest current density for prepared membranes in H2/O2 single cell at 100% relative humidity and 80°C is 1900 mA.cm−2.

Oxygen environment and metabolic oxygen demand predictably interact to affect thermal behavior in a lizard, Sceloporus occidentalis.

The climate crisis necessitates predicting how organisms respond to changing environments, but this requires understanding the mechanisms underlying thermal tolerance. The Hierarchical Mechanisms of Thermal Limitation (HMTL) hypothesis proposes that respiratory capacity and marginal stability of proteins and membranes interact hierarchically to determine thermal performance and limits. An untested prediction of the HMTL hypothesis is that behavioral anapyrexia (i.e., reduced body temperature in hypoxia) is exacerbated when metabolic demand is high. We tested this prediction by manipulating western fence lizards' (Sceloporus occidentalis) metabolic demand and oxygen environment, then measuring selected body temperatures. Lizards with elevated metabolic demand selected lower body temperatures at higher oxygen concentrations than resting lizards, but this occurred only at oxygen concentrations <12% O2 , suggesting thermal limits are unaffected by naturally-occurring oxygen variation. Given our results and the ubiquity of behavioral anapyrexia, the HMTL hypothesis may generally explain how oxygen and temperature interactively affect reptile performance.

Standard Operating Protocol for Ion-Exchange Capacity of Anion Exchange Membranes

Ion-exchange capacity (IEC) is the measure of a material’s capability to displace ions formerly incorporated within its structure. IEC is a key feature of anion-exchange membranes (AEM), as it determines the AEM’s ability to conduct the ions required to sustain the electrochemical reactions where they are utilized. As an intrinsic property, measuring the IEC accurately is essential to study AEMs and understand their performance within devices. In this method article, a facile and accurate standard operating procedure (SOP) to measure the IEC of AEMs is proposed. When compared to conventional acid-base back-titration or Mohr titration, the proposed method combines the fast reaction between silver and halide ions and the accuracy of the potentiometric titration, providing a convenient and precise protocol for researchers in the field.

MO752: Doping Polysulfone Dialysis Membranes with Human Neutrophil Elastase Inhibitors—A Proof-of-Concept Study

Abstract BACKGROUND AND AIMS The recurrent contact of blood with the haemodialysis (HD) membrane during the treatment procedure, triggers neutrophil activation, leading to an increase of blood levels of neutrophil elastase that contributes to the chronic inflammatory response experienced by end-stage renal disease patients with a consequent increase of morbidity and mortality. Based on our group's experience in developing flat-sheet polysulfone (PSF) membranes by using the spin-coating and phase-inversion methods [1], and in the synthesis of human neutrophil elastase inhibitors (HNEIs), namely 4-oxo-β-lactam-based compounds [2], the successful doping of PSF membranes with HNEIs has been achieved [3]. These PSF-HNEI biomaterials have proven to be bioactive and biocompatible, and they included in house synthetized HNEIs alongside Sivelestat (SIV, a second generation HNEI) PSF membranes [3]. In this study, we took a step forward aiming to test the efficacy of such modified membranes when exposed to biological conditions (human plasma). METHOD SIV (Abcam) and an in house synthesized 4-oxo-β-lactam-based compound (D4L-2) [2], from our library, were used. The IC50 of both HNEIs in HEPES buffer was evaluated by performing an HNE activity assay [2]. PSF membranes were prepared as described elsewhere [1] and doped with each HNEI by adsorption [3]. In 3 independent assays, triplicates of PSF membrane circles (Ø = 0.6 cm) were incubated with HNEIs vehicle (2.5% DMSO) or with 10–2000 nM SIV or D4L-2 during 3 h at 25°C, for HNEIs adsorption. Afterwards, all PSF-HNEI membranes were incubated in diluted plasma (50% PBS, pH 7.4) or HEPES buffer for 3 h at 37°C. The bioactivity of PSF-HNEI membranes was assessed before and after incubation using the HNE activity assay [2]. The value obtained for PSF membranes incubated with HNEIs vehicle was used to normalize the results (0% HNE inhibition). RESULTS The IC50 of SIV and D4L-2 in solution were 32.7 and 18.1 nM, respectively. Before incubation with either plasma or HEPES buffer, the HNE inhibition capacity of both PSF-HNEI membranes increased in a concentration-dependent manner, reflecting the HNEIs solutions used during the adsorption process. The highest HNE inhibition ability was presented by PSF-D4L-2 membranes (91.7% ± 0.9% versus 35.3% ± 5.0%). After incubation, PSF-HNEIs membranes immersed in HEPES buffer showed a similar HNE inhibition (84.5% ± 2.2% and 34.0% ± 6.2% for D4L-2 and SIV, respectively). However, the modified membranes incubated in plasma showed a significant decrease in HNE inhibition (D4L-2: 23.7% ± 1.6% and SIV: 7.0% ± 2.1%). CONCLUSION D4L-2 showed the best performance (lower IC50 value and higher HNE inhibitory capacity of doped membranes), which is in accordance with following the assumption that the 4-oxo-β-lactam-based inhibitors are more stable molecules and present higher specificity for HNE. However, both PSF-HNEI biomaterials seem to have fulfiled the objective for which they were developed, since, after being incubated in plasma, they presented a significant decrease in the capacity to inhibit HNE, showing that the HNEIs immobilized in the membranes had captured/bound to the HNE present in the plasma sample.

A novel temperature-responsive mixed matrix ultrafiltration membrane based on boron nitride nanomaterial

A novel mixed matrix membrane was prepared by blending polysulfone with two-dimensional boron nitride followed by its hydroxyl functionalization. Prepared nanocomposite membranes were characterized for the surface morphology, surface roughness, zeta potential and hydrophilicity. Uniform dispersion of boron nitride nanoparticles in polysulfone matrix and consequent changes in membrane properties were confirmed by scanning electron microscope images, atomic force microscope images, zeta potential, contact angle analysis, and X-Ray photoelectron spectroscopy. Differential scanning calorimetry (DSC) technique was used to determine the glass transition temperature (Tg) of the modified membrane and the results revealed the presence of BN in the membrane matrix. The highest water flux of 329.52 Liters per sqm per hour (LMH) was obtained in case of PS/BN (1%) as compared to 151.87 LMH of virgin membrane and Albumin rejection also increased by nanocomposites membranes up to certain concentration of Boron nitride. A unique behavior of temperature responsiveness of nanocomposite membrane was observed, where a steep increment in permeate flux by 205% at higher temperature was noted as compared to the virgin Polysulfone membrane where only 103% increase was recorded for the same temperature range. Moreover, the water uptake capacity of nanocomposite membranes were measured to understand the changes with nanomaterial incorporation. The membrane showed a good promise for high-temperature separation applications.

An efficient and high-capacity porous functionalized-membranes for uranium recovery from wastewater

In order to satisfy the increasing needs for sustainable development of the nuclear energy industry, it is critical to vigorously develop efficient materials for uranium separation and recovery from wastewater. In this work, novel amidoxime-functionalized membranes (PAO membranes) were successfully synthesized via a facile one-step non-solvent induce phase separation rather than as-reported synthesized approaches that needed complicated additives or harsh reaction conditions. The pore channels provided large specific surface areas and massive binding sites, and the bulk-shape membrane was convenient for collection. Removal of uranium as a function of initial pH, reaction time, initial concentrations of U(VI), and temperature was studied. The maximum adsorption capacity of the PAO membranes toward U(VI) calculated from the Langmuir model was up to 641.72 mg·g−1 at pH 5 and 298 K. Thermodynamic studies indicated that the enrichment of U(VI) was a spontaneous and endothermic process. The removal percentage of uranium reached 86.50% in simulated wastewater in the case of multiple coexisting metal ions. In addition, the scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results confirmed that the abundant adsorption sites of the PAO membranes were responsible for the efficient immobilization of uranium by forming chelating species, especially amidoxime groups and carboxyl groups. This work presents a novel strategy for mass production of a new generation of high-efficiency adsorbents for uranium-containing wastewater treatment in the future.

Evaluation of chiral separation by Pirkle-type chiral selector based mixed matrix membranes

In the present approach, the chiral resolution capacity of mixed matrix membranes (MMMs) containing silicon-based mesoporous array (named MCM-41) and grafted with Pirkle-type chiral selector is presented. The mesoporous structure was prepared via the hydrothermal method and the polyethersulfone (PES)-based MMMs were obtained from the phase inversion method. The eco-friendly and sustainable synthesis of the mesoporous architecture from the use of silicon-rich waste proved to be efficient, since the MCM-41 structure exhibited interesting textural and structural features, such as high porosity, large pore volume, uniform pore diameter, and high surface area. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) measurements were useful to confirm the presence of MCM-41-Pirkle within the MMMs. The performance of the MMMs was evaluated through filtration tests with the analyte 2,2,2-trifluoro-1-(9-anthryl) ethanol (Pirkle’s alcohol). The concentration of both enantiomers throughout the filtration was monitored by liquid chromatography (LC) using L-phenylglycine column Regis® Technologies (25 cm, 4.6 mm d.i., 5 µm). The MCM-41-Pirkle incorporated within the PES matrix exhibited a good enantioselectivity (α = 1.28) and 45% of the (R)-Pirkle's alcohol was retained. According to our findings, this nano-architectured material can be considered a relevant alternative with great potential for chiral separations in polymeric membrane technology.

Imidazole-doped proton conducting composite membranes fabricated from double-crosslinked poly(vinyl alcohol) and zeolitic imidazolate framework

Proton conducting membranes were fabricated from double-crosslinked poly(vinyl alcohol) and zeolitic imidazolate framework (ZIF). The effect of the ZIF type (ZIF-8, ZIF-67, and a 1:1 wt/wt. mixture (ZIF-mix)) on water uptake, ion exchange capacity, proton conductivity, and oxidative stability of the composite membranes was studied. The membrane comprising ZIF-mix exhibited the highest proton conductivity, suggesting a synergistic effect between ZIF-8 and ZIF-67. The influence of ZIF-mix content on the membrane properties was further investigated, and the optimum loading was 7.5%. The introduction of ZIF-mix provided an improvement in proton conductivity and mechanical strength. Moreover, all composite membranes demonstrated low water uptake, low methanol uptake, adequate thermal stability, and high oxidative stability. To the best of our knowledge, this was the first time a ZIF-mix composite membrane was doped with imidazole to improve proton conductivity under non-humidified conditions. The proton conductivity of the imidazole-doped 7.5%ZIF-mix membrane increased with increasing imidazole content and temperature.

Impact of local and systemic antimicrobials on leukocyte- and platelet rich fibrin: an in vitro study

The aim of this study was to evaluate the effect of local and systemic administration of antimicrobials to leukocyte- and platelet-rich fibrin (L-PRF). For part A, 16 tubes of venous blood were collected from each of eight systemically healthy subjects. Prior to blood centrifugation, 12 of the 16 tubes were injected with 0.125 ml, 0.25 ml or 0.50 ml metronidazole solution. One set of L-PRF membranes was used to assess the release of vascular endothelial growth factor AB, platelet-derived growth factor, transforming growth factor beta 1, and bone morphogenetic protein 2 at indicated time points. The metronidazole release over time by L-PRF membranes was also evaluated. The remaining L-PRF membranes were placed on the surface of agar plates inoculated with three different periodontal pathogens to determine their antibacterial activity. For part B, another six subjects were enrolled with three subjects taking 2 g amoxicillin and three subjects 500 mg metronidazole as prophylaxis prior to a periodontal treatment. Before and 2 h after consuming one of the prescribed antimicrobials, three tubes of blood were collected for preparing L-PRF membranes. These membranes were used to measure the antibacterial activity against periodontal pathogens. No statistically significant difference could be found in the release of growth factors between L-PRF membranes with and without incorporation of metronidazole solution. The release of metronidazole could be detected up to day 3, however with the highest concentration during the first 4 h. This concentration was dose dependent. The antibacterial capacity of L-PRF membranes increased significantly for both the systemic intake, and after the addition of metronidazole solution to the blood tubes before centrifugation, the latter again dose dependent. The antibacterial capacity of L-PRF against the periodontal pathogens tested can significantly be enhanced by the addition of antimicrobials, without disadvantage for the release of growth factors.

Interface electrode and enhanced actuation performance of SiO2-GO/PFSA-based IPMC soft actuators

In this study, ‘three-dimensional structure’ nanohybrid particle (SiO2-GO) were synthesized by in situ hydrolysis and composited with perfluorosulfonic acid (PFSA) to increase the water uptake (WUP) and ion exchange capacity (IEC) of the cast membranes. Ionic polymer metal composite (IPMC) soft actuators were fabricated based on the cast pure PFSA, GO/PFSA and SiO2-GO/PFSA membranes. The morphology and properties of IPMC were researched, and the relationship between them was analyzed in this article. The mechanism of SiO2-GO particles enhancing the properties of IPMC was revealed. The effects of incorporating GO and SiO2-GO on IPMC actuators were analyzed using physicochemical and electromechanical measurements comparing with the corresponding behavior of pure PFSA-based IPMC actuators. Morphology of IPMC showed effective incorporation of GO and SiO2-GO and clarified the dependency of Pt interface electrode on the SiO2-GO content of the PFSA membranes. The addition of SiO2-GO increased dramatically the WUP and IEC of the PFSA membranes and autuation performance of the IPMC actuators. The IPMC with 1 wt% SiO2-GO showed superb properties. The displacement of 1 wt% SiO2-GO under 3 V AC voltage reached 28.4 mm, which is 3.2 times higher than that of the pure PFSA. The maximum displacement under DC voltage reached 44.7 mm (5.5 V), and the blocking force reached 43.2 mN (5 V), which increased respectively 1.1 times and two times.

CF3-MOF enhanced pervaporation selectivity of PDMS membranes for butanol separation

Direct separating butanol from fermentation broth via pervaporation is considered as the most effective method to realize solvent enrichment, which is dominated by membranes. Herein, MOF (MAF-9) with CF3 group is doped into PDMS matrix to enhance the butanol pervaporation, especially selectivity. The super-hydrophobicity of MAF-9 caused by CF3 groups allows the preferential adsorption and permeation for butanol molecules, thus increasing the membrane selectivity; while its appropriate pore diameter renders the exquisite diffusion pathways towards the butanol molecules, thus increasing the membrane flux. Results show that the loading-optimized MAF-9/PDMS MMM has 53 of separation factor and 848 g m−2 h−1 of membrane flux, which are increased by 24% and 16%, respectively, compared with pure PDMS membrane. TGA, FT-IR, BET, and XRD are conducted to characterize the thermal stability, morphology and structure of MAF-9; PALS, SEM, AFM, SD and TGA are tested to evaluate the free volume property, morphology, adsorption capacity and thermal stability of membranes, respectively. Conditions including particle loading, feed temperature and feed concentration are also optimized in this study.

Enhanced performance of novel carbon nanotubes - sulfonated poly ether ether ketone (speek) composite proton exchange membrane in mfc application

Sulfonated poly ether ether ketone (SPEEK) nanocomposite proton exchange membrane (PEM) was prepared by incorporating multi-walled carbon nanotubes (CNT) at different weight percentages for microbial fuel cell (MFC) applications. Physico-chemical, thermal, mechanical and morphological characteristics of the prepared CNT-SPEEK composite membranes were analyzed using various techniques. Further, the water uptake capacity, Ion exchange capacity (IEC) and MFC performance of the CNT-SPEEK composite membranes were evaluated and compared with the pristine SPEEK membrane. Results show that incorporation of CNTs in SPEEK membranes exhibited a better water uptake capacity (34.18%–36.02%) and IEC (1.94–2.15 meq/g) compared to the SPEEK membrane. Improvement in membrane properties resulted in 2-fold higher power density compared to SPEEK membrane. Composite membrane with 0.75% CNT-SPEEK produced the higher power density (1.77 W/m2) in comparison with all the membranes evaluated. Chemical oxygen demand (COD) removal efficiency values of the MFC with SPEEK composite membranes were also found to be around 90%. Overall, the results reveal that CNT-SPEEK composite membrane as a potential PEM for MFC applications.

The Effect of Sulfated Zirconia and Zirconium Phosphate Nanocomposite Membranes on Fuel-Cell Efficiency.

To investigate the effect of acidic nanoparticles on proton conductivity, permeability, and fuel-cell performance, a commercial Nafion® 117 membrane was impregnated with zirconium phosphates (ZrP) and sulfated zirconium (S-ZrO2) nanoparticles. As they are more stable than other solid superacids, sulfated metal oxides have been the subject of intensive research. Meanwhile, hydrophilic, proton-conducting inorganic acids such as zirconium phosphate (ZrP) have been used to modify the Nafion® membrane due to their hydrophilic nature, proton-conducting material, very low toxicity, low cost, and stability in a hydrogen/oxygen atmosphere. A tensile test, water uptake, methanol crossover, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to assess the capacity of nanocomposite membranes to function in a fuel cell. The modified Nafion® membrane had a higher water uptake and a lower water content angle than the commercial Nafion® 117 membrane, indicating that it has a greater impact on conductivity. Under strain rates of 40, 30, and 20 mm/min, the nanocomposite membranes demonstrated more stable thermal deterioration and higher mechanical strength, which offers tremendous promise for fuel-cell applications. When compared to 0.113 S/cm and 0.013 S/cm, respectively, of commercial Nafion® 117 and Nafion® ZrP membranes, the modified Nafion® membrane with ammonia sulphate acid had the highest proton conductivity of 7.891 S/cm. When tested using a direct single-cell methanol fuel cell, it also had the highest power density of 183 mW cm−2 which is better than commercial Nafion® 117 and Nafion® ZrP membranes.

The Response of Tomato Fruit Cuticle Membranes Against Heat and Light.

Two important biophysical properties, the thermal and UV-Vis screening capacity, of isolated tomato fruit cuticle membranes (CM) have been studied by differential scanning calorimetry (DSC) and UV-Vis spectrometry, respectively. A first order melting, corresponding to waxes, and a second order glass transition (Tg) thermal events have been observed. The glass transition was less defined and displaced toward higher temperatures along the fruit ripening. In immature and mature green fruits, the CM was always in the viscous and more fluid state but, in ripe fruits, daily and seasonal temperature fluctuations may cause the transition between the glassy and viscous states altering the mass transfer between the epidermal plant cells and the environment. CM dewaxing reduced the Tg value, as derived from the role of waxes as fillers. Tg reduction was more intense after polysaccharide removal due to their highly interwoven distribution within the cutin matrix that restricts the chain mobility. Such effect was amplified by the presence of phenolic compounds in ripe cuticle membranes. The structural rigidity induced by phenolics in tomato CMs was directly reflected in their mechanical elastic modulus. The heat capacity (Cprev) of cuticle membranes was found to depend on the developmental stage of the fruits and was higher in immature and green stages. The average Cprev value was above the one of air, which confers heat regulation capacity to CM. Cuticle membranes screened the UV-B light by 99% irrespectively the developmental stage of the fruit. As intra and epicuticular waxes contributed very little to the UV screening, this protection capacity is attributed to the absorption by cinnamic acid derivatives. However, the blocking capacity toward UV-A is mainly due to the CM thickness increment during growth and to the absorption by flavone chalconaringenin accumulated during ripening. The build-up of phenolic compounds was found to be an efficient mechanism to regulate both the thermal and UV screening properties of cuticle membranes.

Получение и свойства ультрафильтрационных мембран из ацетата целлюлозы на подложке из нейлоновой сетки

Composite membranes nylon-AC (NAC) were obtained by immersing a nylon mesh substrate in a 5 % solution of cellulose acetate (AC) in acetone. The AC content in the membrane ranged from 21 to 45 %, depending on the number of applied surface layers. According to the results of studying the properties of composite membranes, an increase in water absorption and total porosity of membranes after the application of the first layer of AC was found, and with the application of the next layer of AC, the values of water absorption and total porosity slightly decrease, which is due to the compaction of the membrane structure. Also, a decrease in the contact angle of the membrane wetting by 33° was revealed, which means an increase in the hydrophilic properties of the membrane, which increases the wettability and productivity of the obtained membranes. Composite membranes with two and three layers of AC: NAC2 and NAC3 were used to separate 0.5 % water-oil emulsion with particle sizes from 81 to 422 nm. The specific productivity of the NAC2 membrane by 0.5 % water-oil emulsion was 9433 dm3/(m2·h), the productivity of the NAC3 membrane was 3799 dm3/(m2·h) at a pressure of 0.55 MPa, which exceeds the performance of the commercial ultrafiltration membrane UPM-100 equal to 1843 dm3/(m2·h). According to the results of the study, the retention capacity of composite membranes for oil products from a water-oil emulsion was established, which was 61 % for NAC2 membranes and 75 % for NAC3 membrane. These indicators are not inferior to the retention capacity of a commercial ultrafiltration membrane of the UPM-100 brand.