Influence Of Membrane Properties Research Articles

Methacrylated chitosan/jellyfish collagen membranes as cell instructive platforms for liver tissue engineering

Although the multidisciplinary area of liver tissue engineering is in continuous progress, research in this field is still focused on developing an ideal liver tissue template. Innovative strategies are required to improve membrane stability and bioactivity.In our study, sustainable biomimetic membranes were developed by blending methacrylated chitosan (CSMA) with jellyfish collagen (jCol) for liver tissue engineering applications.The in vitro biological behaviour demonstrated the capability of the developed membranes to create a suitable milieu to enable hepatocyte growth and differentiation. The functionalization of chitosan together with the biocompatibility of marine collagen and the intrinsic membrane properties offered the ideal biochemical, topographical, and mechanical cues to the cells. Thanks to the enhanced CSMA/jCol membranes' characteristics, hepatocytes on such biomaterials exhibited improved growth, viability, and active liver-specific functions when compared to the cell fate achieved on CSMA membranes. Our study provides new insights about the influence of membrane properties on liver cells behaviour for the design of novel instructive biomaterials. The enrichment of functionalized chitosan with marine collagen represents a promising and innovative approach for the development of an appropriate platform for hepatic tissue engineering.

Carbon dioxide absorption in a gas-liquid membrane contactor: Influence of membrane properties and absorbent chemistry

The present work demonstrates the performance of hollow fibre membranes fabricated using polyvinyl chloride, polystyrene (EPS) and polydimethylsiloxane (PDMS) coupled with 30% monoethanolamine (MEA) in a gas liquid membrane contactor (GLMC) for the absorption of carbon dioxide. A gas mixture with a composition of (50/50 v/v%) methane (CH4) and (CO2) was used to assess the efficiency of the prepared membranes in the removal of carbon dioxide. Then HFM 3 which showed high CO2 removal was used to separate a mixture of nitrogen (N2)/oxygen(O2)/carbon dioxide (CO2) with a composition of (73/18/9 v/v%), respectively. Four different absorption liquids: 30 % MEA solution, 30 % EDA solution, 30 % MEA – graphene oxide (GO) and 30 % EDA-GO nanofluids were coupled with HFM3 to analyse the efficiency of the different amine liquids in CO2 absorption in GLMC. The 30 % EDA-GO solution showed an increase in the efficiency of CO2 absorption. The nanofluids showed an enhancement factor for CO2 absorption in the nanofluid was 121 % and 117 % for MEA-GO and EDA-GO, respectively. This enhancement was attributed to the hydrodynamic effects and Brownian motion of graphene oxide in the amine liquids. 30 % EDA solution infused with 0.2 mg/ml graphene oxide nanoparticles achieved the highest loading of carbon dioxide 0.25 mol/ cm3.

Direct conversion of CO2 to dimethyl ether in a fixed bed membrane reactor: Influence of membrane properties and process conditions

The direct hydrogenation of CO2 to dimethyl ether (DME) is a promising technology for CO2 valorisation. In this work, a 1D phenomenological reactor model is developed to evaluate and optimize the performance of a membrane reactor for this conversion, otherwise limited by thermodynamic equilibrium and temperature gradients. The co-current circulation of a sweep gas stream through the permeation zone promotes both water and heat removal from the reaction zone, thus increasing overall DME yield (from 44% to 64%). The membrane properties in terms of water permeability (i.e., 4·10−7 mol·Pa−1m−2s−1) and selectivity (i.e., 50 towards H2, 30 towards CO2 and CO, 10 towards methanol), for optimal reactor performance have been determined considering, for the first time, non-ideal separation and non-isothermal operation. Thus, this work sheds light into suitable membrane materials for this applications. Then, the non-isothermal performance of the membrane reactor was analysed as a function of the process parameters (i.e., the sweep gas to feed flow ratio, the gradient of total pressure across the membrane, the inlet temperature to the reaction and permeation zone and the feed composition). Owing to its ability to remove 96% of the water produced in this reaction, the proposed membrane reactor outperforms a conventional packed bed for the same application (i.e., with 36% and 46% improvement in CO2 conversion and DME yield, respectively). The results of this work demonstrate the potential of the membrane reactor to make the CO2 conversion to DME a feasible process.

Study of Anion Exchange Membrane Properties Incorporating N-spirocyclic Quaternary Ammonium Cations and Aqueous Organic Redox Flow Battery Performance.

Flexible cross-linked anion exchange membranes (AEMs) based on poly (p-phenylene oxide) grafted with N-spirocyclic quaternary ammonium cations were synthesized via UV-induced free-radical polymerization by using diallylpiperidinium chloride as an ionic monomer. Five membranes with ion exchange capacity (IEC) varying between 1.5 to 2.8 mmol Cl−·g−1 polymer were obtained and the correlation between IEC, water uptake, state of water in the membrane and ionic conductivity was studied. In the second part of this study, the influence of properties of four of these membranes on cell cycling stability and performance was investigated in an aqueous organic redox flow battery (AORFB) employing dimethyl viologen (MV) and N,N,N-2,2,6,6-heptamethylpiperidinyl oxy-4-ammonium chloride (TMA-TEMPO). The influence of membrane properties on cell cycling stability and performance was studied. At low-current density (20 mA·cm−2), the best capacity retention was obtained with lower IEC membranes for which the water uptake, freezable water and TMA-TEMPO and MV crossover are low. However, at a high current density (80 mA·cm−2), membrane resistance plays an important role and a membrane with moderate IEC, more precisely, moderate ion conductivity and water uptake was found to maintain the best overall cell performance. The results in this work contribute to the basic understanding of the relationship between membrane properties and cell performance, providing insights guiding the development of advanced membranes to improve the efficiency and power capability for AORFB systems.

Cavitation bubble dynamics in a vicinity of a thin membrane wetted by different fluids

Understanding and controlling the interaction of cavitation bubbles and nearby material is becoming essential optimization of various processes. We examined the interaction of a single bubble with a membrane with different fluids on each side of it. Significant differences in bubble behavior depending on the fluid properties were observed, while the influence of membrane properties was less pronounced. The study has important implications, such as optimization of sonoporation (targeted drug delivery) where the mechanism, by which the permeability of the membrane is increased, is still not well understood. These results show that the focus of the optimization process should, in the first place, lie on the properties of liquids, rather than the mechanical properties of the membrane itself.

A Critical Review of Membrane Wettability in Membrane Distillation from the Perspective of Interfacial Interactions.

Hydrophobic membranes used in membrane distillation (MD) systems are often subject to wetting during long-term operation. Thus, it is of great importance to fully understand factors that influence the wettability of hydrophobic membranes and their impact on the overall separation efficiency that can be achieved in MD systems. This Critical Review summarizes both fundamental and applied aspects of membrane wetting with particular emphasis on interfacial interaction between the membrane and solutes in the feed solution. First, the theoretical background of surface wetting, including the relationship between wettability and interfacial interaction, definition and measurement of contact angle, surface tension, surface free energy, adhesion force, and liquid entry pressure, is described. Second, the nature of wettability, membrane wetting mechanisms, influence of membrane properties, feed characteristics and operating conditions on membrane wetting, and evolution of membrane wetting are reviewed in the context of an MD process. Third, specific membrane features that increase resistance to wetting (e.g., superhydrophobic, omniphobic, and Janus membranes) are discussed briefly followed by the comparison of various cleaning approaches to restore membrane hydrophobicity. Finally, challenges with the prevention of membrane wetting are summarized, and future work is proposed to improve the use of MD technology in a variety of applications.

Pervaporation performance of crosslinked PVA membranes in the vicinity of the glass transition temperature

This work investigates the pervaporation performance of crosslinked poly (vinyl alcohol) (PVA) membranes for ethanol dehydration near the glass transition. The solubility of water and ethanol mixture in the membranes was measured as a function of feed composition and sorption temperature, and the data was modelled by perturbed-chain statistical associating fluid theory (PC-SAFT). Importantly, this approach allows the solubility of the two components to be determined individually. Model results show that the heat of sorption of water and ethanol was constant across the temperature range. Water permeance generally decreased when operational temperature increased, indicating a solubility-controlled transport behavior. The permeance also increased when water feed concentration increased. Activation energy analysis provided more insights about the influence of membrane properties on the mass transport mechanism. At 90 wt% ethanol feed composition, the apparent activation energy (Ea) for water permeation changed from 9.6 kJ mol−1 when temperature was < 70 °C to − 9.1 kJ mol−1 when temperature was > 80 °C. When the feed composition decreased to 80 wt% ethanol, a transition was observed at a lower temperature range (60–65 °C). These changes were related to changes in the activation energy of diffusion, given the heat of sorption was constant. The permeability of ethanol was lower due to its larger molecular size, but a similar transition was observed for the 80 wt% ethanol case.

Influence of Membrane Properties on Pineapple Wine Clarification and Fouling Behavior

The experiment was carried out to investigate the influence of membrane pore size and hydrophobicity on the quality of clarified pineapple wine and fouling characteristics, using stirred cell dead–end microfiltration. The test membranes were mixed cellulose acetate (MCE, pore size 0.45 and 0.22 μm), modified polyvinylidene fluoride (MPVDF, 0.22 μm) and polyethersulfone (PESF, 0.22 μm). It was found that all types of membrane successfully clarified the pineapple wine. The membrane pore size and hydrophobicity played an importance role in membrane fouling, both reversible and irreversible. Regarding the permeate flux and fouling, 0.45 μm MCE was the most suitable for pineapple wine clarification. However, intensive organoleptic test with pilot scale would be needed.

A study on the stability of polyethersulfone ultrafiltration membranes in a photocatalytic membrane reactor

To date no information about the stability of the polymer membranes in photocatalytic membrane reactors (PMRs) has been published. In order to implement this technology into the full scale the lifespan of the membranes should be assessed. In this paper the investigations on the influence of membrane properties, type of a TiO2 photocatalyst (P25, ST-01, A700, and A800), a presence of oxidative species and the process parameters such as feed cross flow velocity and transmembrane pressure (TMP) on the stability of commercial polyethersulfone ultrafiltration membranes with different cut-off in a PMR are presented. Under the conditions prevailing in the PMR all the tested membranes lost their separation properties towards dextrans. The membrane characterized by the finest pores and thus the most delicate skin layer was damaged to the highest extent. The small angular-shaped particles of ST-01 caused a more severe damage of the membrane surface than the large round-edge shaped particles of A800. The deterioration of the membrane separation properties was less severe at low (1bar) TMP value compared to that at TMP of 3bar. The loss of the separation properties of the membranes was caused to a greater extent by the abrasion of their surface by the photocatalyst particles than by the action of oxidative species.

Influence of membrane properties on the transient behavior of polymer electrolyte fuel cells

Understanding the performance of proton exchange membrane (PEM) fuel cells is critical to the water management in the fuel cell system. Low-humidity operating conditions present a complex interaction between dynamic behavior and water transport owing to different time scales of water transport mechanisms in the transient process. Toward understanding the effects of membrane properties on the dynamic behavior, this paper presents numerical simulations for a single channel PEM fuel cell undergoing changes in load, by subjecting the unit cell to step change in current. The complex interaction between cell voltage response and water transport dynamics for various membrane properties is explored in detail, where the performance is critically related to the water content of the membrane. Detailed computational fluid dynamics (CFD) simulations are carried out to show that step increase in current density leads to anode dryout due to electro-osmotic drag, and to investigate the dependence of transient behavior on the variations in membrane properties. The results show that water uptake by the membrane is a crucial factor in determining the occurrence of anode dryout and hence voltage reversal, and can be avoided by a graded membrane design.

Regulatory role of membrane fluidity in gene expression and physiological functions

Plants, algae, and photosynthetic bacteria experience frequent changes in environment. The ability to survive depends on their capacity to acclimate to such changes. In particular, fluctuations in temperature affect the fluidity of cytoplasmic and thylakoid membranes. The molecular mechanisms responsible for the perception of changes in membrane fluidity have not been fully characterized. However, the understanding of the functions of the individual genes for fatty acid desaturases in cyanobacteria and plants led to the directed mutagenesis of such genes that altered the membrane fluidity of cytoplasmic and thylakoid membranes. Characterization of the photosynthetic properties of the transformed cyanobacteria and higher plants revealed that lipid unsaturation is essential for protection of the photosynthetic machinery against environmental stresses, such as strong light, salt stress, and high and low temperatures. The unsaturation of fatty acids enhances the repair of the damaged photosystem II complex under stress conditions. In this review, we summarize the knowledge on the mechanisms that regulate membrane fluidity, on putative sensors that perceive changes in membrane fluidity, on genes that are involved in acclimation to new sets of environmental conditions, and on the influence of membrane properties on photosynthetic functions.

Neck-size distributions of through-pores in polymer membranes

Abstract Capillary flow porometry (CFP) is used for measuring the most constricted part (bottleneck) of through-pores in synthetic membranes. In present work, a systematic study has been carried out to evaluate influence of membrane properties like tortuosity, intersecting pores and thickness on CFP. For evaluating CFP, the track-etched membranes were used as these membranes have cylindrical pores. The average, maximum and minimum pore diameters and pore-diameter distributions in the track-etched membranes were obtained by CFP, and compared with the values obtained by different techniques like atomic force microscopy (AFM), scanning electron microscopy (SEM) and molecular weight cut-off (MWCO). The internal architecture of pore in the track-etched membranes was studied by growing gold nano-rods in the pores. The gold nano-rods were grown in the membrane by electrodeposition using removable electrode (Hg). The transmission electron microscopy (TEM) of nano-gold rods were carried out after dissolution of the membranes in dichloromethane. The studies carried out in the present work showed that: (i) the CFP data remained practically independent of the membrane thickness and tortuosity, (ii) it measured the most constricted diameter of a pore independent of pore-architecture, and (iii) mean flow pore-diameters data were highly reproducible (±5%). The capability of CFP for assessing quality of the membrane was demonstrated using the pore-filled membrane samples having different amounts of the crosslinked poly- N -isopropylacrylamide (poly-NIPA). These samples were prepared by UV-initiator induced in situ photo-polymerization of NIPA in pores of the host microporous poly(propylene) membrane.

The influence of membrane properties on the Silt Density Index

The Silt Density Index (SDI) is commonly applied as a measure for the fouling potential of particles in RO and NF feed waters. The accuracy and reproducibility of the SDI test is increasingly questioned. In this work, the influence of membrane properties on the SDI value is investigated. Eight commercial ‘0.45 μm’ membrane types made of different materials (PVDF, PTFE, acrylic copolymer, nitro cellulose, cellulose acetate, nylon 6,6, and polycarbonate) were used to measure the SDI. Three samples were randomly chosen from each membrane type (same lot), and several membrane properties were studied (pore size distribution, pore shape, surface and bulk porosity, thickness, surface charge, contact angle and surface roughness). SDI values for an artificial feed, composed of a solution of α – alumina particles of 0.6 μm diameter, were determined. The characterization of these membranes shows variation between the membranes used in this study (M1–M8), and within a batch of one membrane type. Substantial differences were found in the SDI values for the different types of membrane filters used. Pore size, porosity and thickness are the most important membrane properties and determine the membrane resistance. Using a membrane with high a membrane resistance results in a low SDI value. The variations in measured SDI values between batches and within a batch are large and explain, at least partly, the problems encountered in practice with unacceptable variations in SDI values. These observed differences make the test unreliable. The variations are attributed to differences in properties of the membranes used. In order to make the SDI a reliable fouling index, there is a very strong need for membrane filters with uniform and constant properties.

Effect of membrane properties on chromium(III) recirculation from concentrate salt mixture solution by nanofiltration

This paper presents results concerning the influence of membrane properties on effective recirculation of chromium(III) from tannery wastewater by nanofiltration process. DK, HL, DL “thin film” membranes and asymmetric CK membrane were tested for theirs permeability and selectivity on model chromium solution contained 2 gCr 3+/dm 3, 10 gCl −/dm 3 and 10 gSO 4 2−/dm 3. Presented results allowed to conclude that both the high permeability and selectivity of NF membranes used for chromium recirculation from low pH, concentrate salt mixture solution are dependent on the membrane surface charge phenomenon. The retaining of the high permeate flux of chromium tannery wastewater at pH below 4, required the use of membranes with their IP as low as possible to assured the negative NF membrane surface charge and low chloride ions retention equal to 7–11%. As a consequence the polarization effect was reduced and the increase of permeate flux was observed. The use of such membranes guarantees obtaining of both a high permeate flux and a concentrated solution of chromium(III) as retentate which is suitable for recirculation. Due to the fouling and aggressive conditions characterized the tanning wastewater the polyamide/polysulfone membranes are suggested. The cellulose acetate membranes do not ensure satisfied results during treatment of tannery wastewater.

Influence of membrane properties on physically reversible and irreversible fouling in membrane bioreactors

This study aimed to examine the impact of membrane properties on membrane fouling in membrane bioreactor (MBR). Membrane fouling was divided into two categories: physically reversible and irreversible fouling. Membrane properties related to each type of membrane fouling were investigated separately. Five microfiltration (MF) and one ultrafiltration (UF) membranes with different properties (pore size, contact angle, roughness, zeta potential, and pure water permeability) were examined with a laboratory-scale MBR, fed with synthetic wastewater. Two separate experiments were conducted: the first to examine physically reversible fouling, and the second to examine physically irreversible fouling. The correlation between the degree of each type of fouling and membrane properties was studied. High correlation was observed between the degree of physically reversible fouling and roughness (R(2)=0.96). In contrast, with regard to physically irreversible fouling, strong correlation between roughness and degree of membrane fouling can only be found in the case of MF membranes. Except for the membrane with the highest roughness, the degree of physically irreversible fouling can be well correlated with pure water permeability (lower pure water permeability results in higher degree of physically irreversible fouling) including UF membrane. On the basis of the results obtained in this study, it can be concluded that roughness is an important factor in determination of physically reversible fouling regardless of the types of membrane (i.e. MF or UF membranes) and evolutions of physically irreversible fouling can be mitigated when an MBR is operated with membranes with smooth surface and high pure water permeability.

Influence of membrane properties on fouling in submerged membrane bioreactors

Polymeric flat-sheet membranes with different properties were used in filtration experiments with activated sludge from a pilot-scale MBR to investigate the influence of membrane pore size, surface porosity, pore morphology, and hydrophobicity on membrane fouling. An improved flux-step method was used to measure both the critical flux and critical flux for irreversibility. Long term experiments were performed to evaluate if influences of membrane properties on short term could be translated to long term fouling behavior. The results showed that a hydrophilic asymmetric membrane with an interconnected pore structure, a nominal pore size of 0.3 μm, and large surface porosity of 27%, provided the best membrane performance with respect to critical flux and critical flux for irreversibility. The dominant fouling mechanism in long term filtration experiments was gel layer formation, which for this membrane was the least severe, and therefore extended the sustainable time.

Influence of membrane properties on spike synchronization in neurons: theory and experiments

In the brain spike synchronization in neurons is involved in information transfer and certain forms of dysfunction. The theory of random point processes was used to relate the statistical properties of input point processes to synchronization between firing in neurons viewed as threshold devices. Derived analytical relations describe normalized synchronization in the case of shared input with balanced excitation and inhibition. For neuronal models with unbalanced shared input and spike generating Hodgkin-Huxley type conductances, the theory satisfactorily describes the temporal dependence of spike synchronization on the delay between spikes. Computer generated stochastic stimulus current was used to stimulate motoneurons in turtle spinal cord slices. Theory was able to approximate the temporal dependence of spike synchronization on the delay between spikes when the membrane time constant and the relative spike threshold measured were used in calculations. In agreement with the theoretical prediction, normalized spike synchrony was reduced when the threshold for spike generation was lowered by injection of steady depolarizing bias current. In spinal motoneurons the relative spike threshold can be lowered by a persistent inward current facilitated by activation of certain metabotropic transmitter receptors. After induction of this inward current spike synchronization was reduced several times. It is suggested that downregulation of the persistent inward current in motoneurons by disruption of brainstem modulatory systems, as in Parkinson disease, can facilitate tremor due to the increased synchrony between motoneurons.

Influence of membrane properties on spike synchronization in neurons: theory and experiments

In the brain spike synchronization in neurons is involved in information transfer and certain forms of dysfunction. The theory of random point processes was used to relate the statistical properties of input point processes to synchronization between firing in neurons viewed as threshold devices. Derived analytical relations describe normalized synchronization in the case of shared input with balanced excitation and inhibition. For neuronal models with unbalanced shared input and spike generating Hodgkin–Huxley type conductances, the theory satisfactorily describes the temporal dependence of spike synchronization on the delay between spikes.Computer generated stochastic stimulus current was used to stimulate motoneurons in turtle spinal cord slices. Theory was able to approximate the temporal dependence of spike synchronization on the delay between spikes when the membrane time constant and the relative spike threshold measured were used in calculations. In agreement with the theoretical prediction, normalized spike synchrony was reduced when the threshold for spike generation was lowered by injection of steady depolarizing bias current.In spinal motoneurons the relative spike threshold can be lowered by a persistent inward current facilitated by activation of certain metabotropic transmitter receptors. After induction of this inward current spike synchronization was reduced several times. It is suggested that downregulation of the persistent inward current in motoneurons by disruption of brainstem modulatory systems, as in Parkinson disease, can facilitate tremor due to the increased synchrony between motoneurons.

Neosepta microporous ion-exchange membranes in dialysis desalination of immunoglobulin fraction of mouse ascitic fluids

The transport properties of porous cation- and anion-exchange membranes differing in pore size, porosity and ion-exchange capacity have been investigated in order to choose a membrane with an optimal set of properties suitable for the dialysis desalination of immunoglobulins (Igs) ( M w 180 000) of mouse ascitic fluids. The porosity of membranes is controlled by the conditions of synthesis. The membranes were employed in the nontraditional dialysis process combining diffusion and convection. The duration of the process was considerably reduced (from 5 days to 2–6 h) and the Igs were better separated from accompanying low-molecular-weight substances in comparison with conventional dialysis. The influence of membrane properties and counterpressure imposed on the membrane to prevent the dialysate from an unnecessary dilution is discussed.

Influence of Membrane Properties on System Performances in Pervaporation under Concentration Polarization Regime

Abstract The concentration polarization phenomenon was studied in the case of the dehydration by pervaporation of octanol in relatively concentrated solutions (up to 47000 ppm of water in n-octanol). The dependence of the observed performances on the mass transfer properties of the membrane and the boundary layer is analyzed theoretically. Experiments performed with cellulose acetate membranes of different thicknesses at a variable stirring speed in an agitated cell allowed us to determine the parameters of the theoretical model. It appears that the selectivity in pervaporation may depend in a complex way on the mass transfer in the boundary layer due to the possible concentration-dependent coupling of fluxes in the membrane. Results of the simulations of situations in which the membrane characteristics as well as the mass transfer in the liquid phase were changed are given to illustrate the influence of different parameters on the observed performances.