Effect Of Membrane Properties Research Articles

Effect of membrane properties on the odor emanating from training aids for explosive-detecting canines.

Canines are widely used for real-time detection of explosives and have proven to be on par with instrumental methods. Canines are thought to rely largely upon detection of volatile chemical constituents of the explosives, though not necessarily the explosive itself. Hence, it is crucial to understand the odor available to them as generated by training aids. Previous studies have established that the Training Aid Delivery Device (TADD) developed by SciK9 is a reliable training aid that reduces cross-contamination and doubles as a storage device. A TADD comprises a standardized container, a synthetic membrane, a membrane holder, and a lid. In the work presented, activated charcoal strips were placed above and below the TADD membrane to determine the relative amounts of volatiles emitted by dynamite (i.e., ethylene glycol dinitrate (EGDN) and trinitroglycerin (NG)). The strips were eluted and the extracts tested using gas chromatography-mass spectrometry in negative ion chemical ionization mode. A series of t-tests at 95% confidence level were performed to determine any differences in vapor composition above and below the membranes. Nine synthetic membranes and six glass fiber membranes were tested in this study. It was expected that the relative concentration of volatiles would remain the same on both sides of the membrane; however, selective removal of nitroglycerin by some membranes was observed. Synthetic membranes with larger pore sizes showed no alteration in the vapor composition. Both synthetic and glass fiber membranes did not show a significant change in relative concentration of the other volatile compound in dynamite, i.e., EGDN. Out of all the membranes tested, three synthetic membranes and four glass fiber membranes showed selective alteration in odor availability of nitroglycerin in dynamite. For training purposes, membranes that do not alter the vapor composition should be used in the training aid.

Understanding adsorption behavior of Polysorbate-20 to sterile filters in therapeutic proteins final filtration process.

Surfactants are commonly used in the therapeutic protein manufacturing process as stabilizer. Polysorbate-20 (PS-20) is one of the most commonly used surfactants to mitigate protein aggregation in the therapeutic protein formulation. It has been observed that polysorbate can be adsorbed by sterile filters during the final filtration process, which poses risk of uneven distribution and potentially reduced polysorbate concentration in final products. In this study, we evaluated the PS-20 adsorption behavior using commonly used sterilizing-grade microfiltration (MF) membranes via a customized filtration set-up. The effect of membrane properties, including the membrane materials, modification, and layer configuration were studied. In addition, the effect of PS-20 concentration was evaluated and the PS-20 adsorption amount by each type of membranes was determined quantitatively and showed good agreement with the in-process adsorption results. Finally, the selection of sterile filters and strategy of pre-flush are discussed for ensuring accurate PS-20 content in the final therapeutic protein drug product.

Thermal modeling of fluid flow and heat transfer in direct contact membrane distillation

In this paper, a mathematical model was developed, and numerical simulations were conducted to analyze the direct contact membrane distillation process (DCMD) utilizing solar energy. The objective is to identify the optimal operating point, flow parameters, dimensions, and membrane properties of membrane module in terms of permeate water flux and GOR. The novel aspect of this paper is to analyze the flow patterns in the feed and permeate regions on performance of DCMD to maximize water production by optimizing the balance between permeate water flux and GOR. Additionally, the study will identify the most suitable location for installing the MD system based on factors such as solar energy availability and average annual temperature. The results show that the polyethylene (PE) membrane provides the highest permeate water flux, while the polytetrafluoroethylene (PTFE) membrane provides the highest GOR. A significant increase in permeate water flux and GOR is observed when the flow changes from laminar to turbulent. The study also examines the effect of membrane module dimensions, where increasing the length decreases flux but increases GOR, while increasing the width increases flux but decreases GOR. The study also reveals that countries with high annual average temperatures produce higher permeate water flux and GOR. The paper also delves into the effect of membrane properties on water flux and GOR. It is observed that a membrane with high porosity, low thickness, and having a pore size greater than 0.14 µm is desirable.

Hydrophobic Membrane for Water Recovery from Humid Gas by Membrane Condenser: Effects of Membrane Properties on Recovered Water Quality

Two hydrophobic porous ethylene-chlorotrifluoroethylene (ECTFE) membranes quenched in water and air were fabricated by thermally induced phase separation and used for water recovery from ammonia-containing humid gas via vapor condensation. The ECTFE membranes were further hydrophobically modified to enhance their condensation performance. The condensate water quality of the modified membrane significantly improved. The mechanisms of the NH3 contamination in the condensate water were discussed. Surface hydrophobic modification slightly increased the flux and recovery stabilities of the membranes. However, the modification also increased the membrane surface roughness, which adversely affects the vapor condensation and droplet evolution on the membrane surface and reduced the recovered water quality. From the material perspective, desirable porous membranes for vapor condensation should have high surface hydrophobicity and smoothness and reasonably large pore sizes. The reasonably large pore sizes would promote noncondensable gaseous contaminants (e.g., ammonia) to go through the membrane, thereby improving the recovered water quality.

The effect of membrane properties on cell growth in an ‘Airway barrier on a chip’

An important factor in determining epithelial cell barrier integrity in an invitro system is the support membrane on which cells are cultured. In this work a custom airway barrier on chip platform was used to investigate the impact of various support membranes on bronchial epithelial cell growth and barrier formation. The membranes had different pore sizes (0.4 μm or 3 μm), densities (1 × 108, 8 × 105, 1.6 × 106 pores/cm2), thicknesses (9 μm, 12 μm, 20 μm) and chemical treatments (polyvinylpyrrolidone or oxidative). Trans Epithelial Electrical Resistance (TER) data for the various cell constructs was compared with cells grown on commercial Transwells®. The results demonstrate differences in barrier integrity and structure, with cells grown under flow having reduced barrier integrity (lower TER) compared to the same cells grown without flow. Bronchial epithelial cells grown in the dynamic (with flow) barrier on a chip platform consistently grew on 0.4 μm pore membranes with higher TERs, compared to 3 μm pore membranes with thinner cell layers due to cell migration where cells translocated to the basolateral region.

Effect of Membrane Properties on the Carbonation of Anion Exchange Membrane Fuel Cells

Anion exchange membrane fuel cells (AEMFC) are potentially very low-cost replacements for proton exchange membrane fuel cells. However, AEMFCs suffer from one very serious drawback: significant performance loss when CO2 is present in the reacting oxidant gas (e.g., air) due to carbonation. Although the chemical mechanisms for how carbonation leads to voltage loss in operating AEMFCs are known1-2, and have even been used to design systems that minimize the exposure of operating AEMFCs to CO2 3, the way that those mechanisms are affected by the properties of the anion exchange membrane (AEM) has not been elucidated. Therefore, this work studies AEMFC carbonation using numerous high-functioning AEMs from the literature – and links their carbonation behavior to their chemical and physical properties4. References Y. Zheng, T. J. Omasta, X. Peng, L. Wang, J. R. Varcoe, B. S. Pivovar and W. E. Mustain, Energy Environ. Sci., 12, 2806–2819 (2019).Y. Zheng, G. Huang, L. Wang, J. R. Varcoe, P. A. Kohl and W. E. Mustain, J. Power Sources, 467, 228350 (2020).Y. Zheng, G. Huang, M. Mandal, J. R. Varcoe, P. A. Kohl and W. E. Mustain, J. Electrochem. Soc., 168, 024504 (2021).Y. Zheng, L. N. Irizarry Colón, N. Ul Hassan, E. R. Williams, M. Stefik, J. M. LaManna, D. S. Hussey and W. E. Mustain, Membranes, 11(2), 102 (2021).

Modulation of reduced graphene oxide membrane for low-fouling wastewater filtration: Membrane structure, wastewater property, and DFT calculation

Membrane fouling is a major hurdle impeding real-world application of membranes for advanced wastewater treatment. In this study, a GO membrane and a reduced GO (rGO) membrane were examined in parallel for their anti-fouling propensities and ability to remove pharmaceutical compounds from realistic wastewater effluents. The effects of membrane properties and wastewater characteristics on the two aspects were also assessed by experiments and DFT simulation. The results showed that the transmembrane pressure (TMP) of the rGO membrane increased by 0–3.5 kPa after filtering a secondary wastewater effluent from an activated sludge system (SW), as compared to 201.6–292.1 kPa for the GO membrane. Meanwhile, slightly greater TMP increases were observed for both membranes after filtering a secondary wastewater effluent from a partial nitrification and denitrification system (PND), but the fouling remained low for the rGO membrane. Overall, chemical reduction of GO to rGO led to larger SSA and reduced negative charge, which promoted adsorptive filtration of pharmaceutical compounds. Also, the diminishing of functional groups possessed by the GO membrane mitigated attractive interlayer polar interaction and expanded membrane pore dimension, thus enhancing the permeability and anti-fouling propensity of GO membranes.

Nanofiltration membranes for salt and dye filtration: effect of membrane properties on performances.

In this study, commercial nanofiltration membranes (Toray, NF 270, Desal 5 L) were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, optical profilometry, contact angle, mechanical strength and zeta potential measurements. Filtration performance tests were conducted with distilled water, MgSO4 solution and synthetic dye solutions, respectively. Among three commercial membranes, the Toray membrane was thought to be better choice. Additional experiments were carried out for a more detailed characterization of the selected membrane. Therefore, firstly, flux and removal efficiency was monitored by using dye solutions at different pH values, and then experiments were carried out to observe the effect of different temperatures. Also, another filtration test with NaCl solution was performed for the Toray membrane. As the main purpose of this study, we aimed to establish a significant correlation between the structural properties of membranes and their performances. In light of the results obtained, it was observed that the contact angle, mechanical strength and surface roughness values of the membrane significantly affected the membrane performance. It was concluded that the most important parameter in dye removal was the zeta potential. As a result of this work, a data set of commercial membranes was created and is available to all membrane users.

The role of ion exchange membrane in vanadium oxygen fuel cell

The effect of membrane properties on the vanadium-oxygen fuel cell performance was studied on a series of commercially available ion exchange membranes of different thickness and ion exchange capacity by selected characterization techniques including electrochemical impedance spectroscopy (ohmic and charge transfer resistance), steady load curves (performance stability) and galvanostatic charge-discharge cycles (efficiencies and capacity decay). Performance stability of the fuel cell was studied under defined conditions (state of charge, temperature, air flow rate) using continuous charging of vanadium electrolyte. In contrast to the previous studies, our results revealed that the membrane affects the fuel cell performance mainly via water management in the catalytic layer of gas diffusion cathode, while vanadium permeation across the membrane has only a minor impact. Generally, the fuel cell shows improved performance stability for more conductive membranes (thinner and with higher ion-exchange capacity), partially due to reduced ohmic losses, but more significantly due to the better ability of the membrane to drain water from the cathode via osmosis, which prevents the flooding of the cathodic catalytic layer. With the optimized membrane, we achieved stable fuel cell performance at the highest current and power density values reported (75 mA cm−2 and 57 mW cm−2 in 50% state of charge).

Effect of Membrane Properties on the Carbonation of Anion Exchange Membrane Fuel Cells.

Anion exchange membrane fuel cells (AEMFC) are potentially very low-cost replacements for proton exchange membrane fuel cells. However, AEMFCs suffer from one very serious drawback: significant performance loss when CO2 is present in the reacting oxidant gas (e.g., air) due to carbonation. Although the chemical mechanisms for how carbonation leads to voltage loss in operating AEMFCs are known, the way those mechanisms are affected by the properties of the anion exchange membrane (AEM) has not been elucidated. Therefore, this work studies AEMFC carbonation using numerous high-functioning AEMs from the literature and it was found that the ionic conductivity of the AEM plays the most critical role in the CO2-related voltage loss from carbonation, with the degree of AEM crystallinity playing a minor role. In short, higher conductivity—resulting either from a reduction in the membrane thickness or a change in the polymer chemistry—results in faster CO2 migration and emission from the anode side. Although this does lead to a lower overall degree of carbonation in the polymer, it also increases CO2-related voltage loss. Additionally, an operando neutron imaging cell is used to show that as AEMFCs become increasingly carbonated their water content is reduced, which further drives down cell performance.

Simulation of direct contact membrane distillation regeneration of liquid desiccant solutions used in air-conditioning

Membrane distillation (MD) has great potential for the treatment of hyper saline waters, including liquid desiccant solutions used in air-conditioning systems. Previous experimental investigations have demonstrated the technical feasibility of MD for regeneration of liquid desiccant solutions. In this study, a direct contact membrane distillation (DCMD) process of the LiCl liquid desiccant solution was simulated using MATLAB software. The simulation was first validated using data obtained from experimental tests. Then, it was used to elucidate the water temperatures, LiCl concentration, and water flux profiles along the membrane leaf inside the DCMD membrane module. Finally, with the help of the simulation, the effects of membrane properties and process operating conditions on the DCMD process performance were systematically examined. The results obtained from this simulation enrich the knowledge and hence facilitate the realization of MD for the liquid desiccant solution regeneration application.

Effect of membrane properties in a membrane rotating biological contactor for wastewater treatment

Membrane fouling is a major drawback of almost all pressure-driven membrane processes that limit their widespread application. This study compares the biological and the hydraulic performances of polyvinylidene fluoride (PVDF) and polysulfone (PSF) membranes when used as external filtration for polishing of a rotating biological contactor (RBC) effluent and as an integrated part in a membrane rotating biological contactor (MRBC). MRBC is an upgrade of the conventional RBC, in which the disk rotations are used not only to provide biological aeration but also as an inherent mechanism for membrane fouling control. Results showed that high biological performances were achieved irrespective of the membrane materials. The steady-state permeabilities of the membranes in MRBC are higher than external filtration by 92.4% and 19.7% for the PVDF and PSF membrane respectively. In the MRBC, smaller membrane-to-disk gaps and high disk rotational speed improve permeability for both membranes reaching the values of 297 and 173 L/(m2 h bar) for PVDF and PSF membranes, respectively. Full-scale energy consumption projection results show that the MRBC consumes only one-fourth of the energy of a referenced membrane bioreactor. The PVDF membrane outperforms PSF membrane thanks to the effective fouling control that maximize the throughput of a lower intrinsic resistance of the PVDF membrane. It implies that apart from membrane material, other operational parameters can still be optimized to further enhance the MRBC performance.

Outdoor air state that may cause moisture condensation in membrane-type total heat exchangers using different membrane materials

Total heat exchanger (THX) is an air-to-air heat exchanger with a heat/moisture exchanging core made of water vapor permeable membrane, it is used to reduce the building energy consumption by recovering both heat and moisture from ventilation air. In hot and humid climate, the membrane surface may get a temperature below the dew point of supply outdoor air, causing moisture condensation at the membrane surface, which may degrade the exchanger performance and increase the health risk. In this research, a mathematical model is built to describe the heat and moisture transfer in the core of a THX, the effects of membrane properties on moisture condensation are analyzed, and the critical outdoor air states for occurrence of the moisture condensation are calculated. The results show that large membrane adsorption constant and large maximum moisture uptake may restrain the moisture condensation, which occurs more easily at the intersection of the supply and exhaust airstreams. The optimal membrane properties are recommended based on a comprehensive consideration of the safety and economy.

Effect of membrane properties on tilted panel performance of microalgae biomass filtration for biofuel feedstock

Efficient membrane-based technology for microalgae harvesting can be achieved via application effective membrane fouling control coupled with appropriate membrane materials. This study explores the combined impact of membrane properties and the tilted panel system on filterability of Euglena sp broth, a potential source of biofuel feedstock. Four membranes from polyvinylidene difluoride (PVDF) and polysulfone (PSF) of PVDF-1, PVDF-3, PSF-1 and PSF-3 were evaluated. Generally, increasing aeration rate, tilting angle and lowering switching period enhance the system performance for all the tested membranes to give the highest permeances of 660, 724, 743 L/m2 h bar, respectively. Those values are among the highest reported in literature. The magnitude of the effect is affected by the membrane properties, mainly by pore size. Tilting without switching configuration is desirable for the membrane with a large pore size (PVDF-1, 0.42 μm) which produced the highest panel permeability of 724.3 (L/m2 h bar), which is >23% higher than the tilted with switching. For this membrane, intermittent aeration applied under switching mode worsened the pore blocking. Membranes with low pore sizes (0.11, 0.04 and 0.03 μm for PVDF-3, PSF-1 and PSF-3, respectively) excelled under switching mode since they are less prone to pore blocking due to smaller pore apertures. Overall results suggest that to gain the full benefit of the tilted panel, operational system of either one-sided without switching or two-sided involving switching must be tailored in conjunction with the desirable properties of the membranes. This finding can help to lower the energy input for microalgae-based biofuel production.

Membrane separation process modeling for CO2 partial removal in prepurification of air separation units

A novel membrane/adsorption hybrid system was proposed for air prepurification in large scale air separation units. Mathematical models were established for cocurrent and countercurrent flow patterns with crude nitrogen as purge stream to describe the membrane separation performance. The experimental and predicted results are in good agreement confirming the validity of the mathematical models. Effects of membrane properties and operation parameters on O2 recovery, N2 recovery, and membrane area requirement were investigated. For countercurrent flow pattern, O2 recovery and N2 recovery were larger than 98 and 99%, respectively, and membrane area requirement was less than 0.25 m2/m3•h−1 with feed side pressure of 0.6 MPa and the purge gas/feed gas ratio of 0.2.

Effect of Membrane Properties on Ion Crossover in Vanadium Redox Flow Batteries

Ion crossover through the membrane is a critical issue associated with the performance and reliability of vanadium redox flow batteries (VRFBs). In this work, we develop a numerical model to investigate the effects of thickness, fixed charge concentration and electro-kinetic permeability of the cation-exchange membrane (CEM) on the ion crossover from diffusion, migration and electro-osmotic convection (EOC) in VRFBs. The cycling performances of VRFBs in different conditions are compared. The results show that thicker membranes reduce the diffusion flux but have little influence on the migration and EOC fluxes. The net vanadium ion crossover from the negative side to the positive side increases with the state-of-charge (SOC), and the thicker membranes lower the asymmetric degree of the vanadium ion crossover between charge and discharge. Both higher fixed charge concentration and enhanced electro-kinetic membrane permeability increase the migration and EOC effects in membranes, and thus increase the crossover of V2+ and V3+; these effects decrease the crossover of VO2+ and VO2+ at discharge, and vice versa for charge. The coulombic efficiency decreases with the increase of the electro-kinetic permeability, and the reduction of coulombic efficiency is more obvious when the membrane fixed charge concentration is higher.

Fouling Behavior of Polyphenols during Model Juice Ultrafiltration: Effect of Membrane Properties

Fruit juice is a complex mixture, in which polyphenols are active compounds for human health. In this paper, the effects of membrane properties, such as materials and molecular weight cutoff (MWCO), on fouling behavior of four typical polyphenols in model fruit juice ultrafiltration process were investigated. Zeta potential, contact angle, SEM image, and fouling resistances were determined. Static adsorption and rejection content of polyphenols on membranes were measured. Quantitative structure-activity relationship (QSAR) model has been developed to demonstrate the relationships between rejection and molecular parameters. Results showed that materials, MWCOs, hydrophobic properties, electrical parameters, and molecular parameters are critical factors. Membranes which were hydrophobic and positively charged have higher permeate flux and lower fouling resistance. Polyphenols were adsorbed by membranes as irreversible fouling and also had an important contribution in cake layer fouling. Retention of polyphenols on polyethersulfon 5-kDa membrane was the largest, while that on PVDF 50-kDa membrane was the least. According to QSAR analysis, rejections of polyphenols were higher when the molecules have smaller dipole moment, larger connectivity index 3Xpv, and smaller 4Xpcv.

The Effect of Membrane Properties on Performance and Transports inside Polymer Electrolyte Membrane Fuel Cells

The primary focus of this work is evaluation, modeling, and comparison of fuel cell properties for a sulfonated aromatic hydrocarbon polymer membrane under fuel cell operations against the standard commercial Nafion membrane. Membrane characterization of transport properties were reported. The fuel cell performance, current distribution mapping, and water balance measurements of both membrane were also examined at different humidity conditions. The studies show that at high RH, the hydrocarbon membrane gives better performance with less water flooding when compared with standard Nafion. However at low RH, where the membrane needs more hydration and conducting of the proton, the standard Nafion membrane shows higher performance than hydrocarbon membrane. Local distributions of current density, water content and liquid water in hydrocarbon membranes were simulated and compared with a Nafion 212 membrane. Both experimental data and model predictions show that the hydrocarbon membrane gives more uniform current distributions than that of the Nafion membrane. The computational model can predict water transport across the membrane and can be used to observe flooding in PEMFC.

Effects of membrane properties on the binding activities of the HN and HC heavy-chain domains of botulinum neurotoxin A

Binding behaviors of the HN and the HC domains of BoNT/A were investigated individually to identify if there exist any differences in their interaction with the cell membrane. Recombinant fragments corresponding to both BoNT/A HN and HC regions were prepared (HN519–845 and HC967–1296) and their binding to synaptic proteins was verified. The binding behaviors of these heavy-chain domains were analyzed by treating the Neuro 2a, a murine neuroblastoma cell line, with compounds known to alter membrane properties. Cholesterol depletion and lipid raft inhibition increased the binding of HN519–845 to Neuro 2a cells without affecting HC967–1296-cell interaction. Sphingolipid depletion decreased the binding of cells to both HC967–1296 and HN519–845 whereas, loading exogenous GD1a, on to the Neuro 2a cells, increased the binding of both the peptides to cells. Microtubule disruption of the Neuro 2a cells by nocodazole decreased the binding of both HC967–1296 and HN519–845 to the treated cells. Inhibition of the clathrin-mediated endocytosis using dynasore, chlorpromazine or potassium (K+) depletion buffer lowered the binding of both HC967–1296 and HN519–845 to the cells, but seemed to exert a more pronounced effect on the binding of HC967–1296 than on the binding of HN519–845. Results indicate that while both the HN and HC domains are involved in the binding of the toxin to neuronal cells there are differences in their behavior which probably stem from their respective amino acid composition and structural location in the toxin three-dimensional structure along with their intended role in translocation and internalization into the cells.

Temporal evolution of the selectivity-permeability relationship during porous membrane filtration of protein solutions

Currently, there is no clear understanding on the effects of membrane properties on temporal evolution of membrane selectivity-permeability relationships during microfiltration or ultrafiltration-based water treatment. In this study, porous polyvinylidene fluoride (PVDF) membrane, polyvinyl chloride membrane, and glass-fiber membrane with distinctive physical and chemical properties were employed to filter bovine serum albumin (BSA) at different pH, coupled with model simulation approaches. Both the experimental results and model prediction showed that, due to the existence of different filtration mechanisms, selectivity of the PVDF membrane and the PVC membrane increase with decreasing permeability, whereas an opposite trend was observed for the glass-fiber membrane. Also, pH strongly affected permeability by changing the zeta potentials of the solutes and the membrane surfaces. Moreover, membrane selectivity was less significantly affected by pH for the polymeric membranes than for the glass-fiber membrane. Practically, high selectivity and permeability may be simultaneously achieved during water treatment by: (1) selection of membranes with suitable pore structure (such as control of solute diameter >1/5 pore diameter); (2) control of feed water condition (such as pH) to suppress intermolecular interactions or solute-membrane interactions, further influence the deposition/adsorption of solute on membrane.