Water Vapor Separation Research Articles

Electrospun nanofiber-supported thin-film composite membrane by introducing graphene oxide interlayer for water vapor/N2 separation

In response to the increasing challenge of global water scarcity, the need for alternative water resources has become increasingly critical. Membrane technologies for water vapor separation have emerged as promising approaches for water recovery and reuse. In this study, a polyethersulfone electrospun nanofiber-supported thin-film composite (eTFC) membrane structure with graphene oxide (GO) interlayer, specifically designed for water vapor/N2 separation was introduced. The interlayer was fabricated by controlling the deposition of GO on the electrospun nanofiber substrate. Subsequently, the thin-film was formed through interfacial polymerization using trimesoyl chloride and piperazine as monomers. All the prepared membranes were characterized using analytical techniques. Their water vapor separation performance was evaluated under different water activity conditions and compared to commercial membrane with similar average pore size. The optimized Gi-eTFC (with a GO interlayer of 0.4 mg) exhibited enhanced hydrophilicity, superior water vapor permeance of 3817 GPU, and a relatively high water vapor/N2 selectivity of 115, under conditions of 80 % relative humidity, 1 bar pressure, and a temperature of 30 °C. Gi-eTFC membranes with an optimized GO interlayer showed uniform and successful polyamide active-layer formation, confirming that the introduction of the GO interlayer and the use of nanofibers had a synergistic effect on improving water vapor separation performance.

The impacts of structural parameters on performance and energy loss of the supersonic separator: A sensitivity analysis

The supersonic separator uses pressure energy to achieve highly efficient carbon capture and water vapor separation from the natural gas mixture. Structural parameters are crucial in determining both separation performance and pressure energy loss of the supersonic separator. However, a comprehensive understanding of how them influence flow behaviors and performance is hindered by their coupling effects and the limitations of numerical methods. This study introduces Euler-Lagrange-Euler model to predict separation performance and pressure energy loss of supersonic dehydration process with varying structural parameters. The results show that the expansion ratio of the divergent section, length of the convergent section, inlet radius of the inner body, and throat radius of the inner body significantly impact separation performance and pressure energy loss. Especially the first parameter, the swirl strength and centrifugal acceleration decay to 0.044 and 2.41 × 104 m s−2 as it increases. At the same time, the droplet removal rate significantly improves, but the separation performance does not increase indefinitely due to the shock waves. The dehydration efficiency first increases to 95.09 % at Er= 1.5 and then decreases; the dew point depression also expands to 25.28 K and then drops, and the corresponding pressure loss rises to 0.47 and then falls.

Pore-filled composite membranes for water vapor separation: Bench-scale advancements and semi-empirical modeling

Efficient scale-up processes of gas separation membranes require a thorough assessment of performance across various parameters. Semi-empirical modeling based on theory and empirical data is an attractive approach to predict the required performance. Despite numerous studies on the performance of gas separation membranes depending on internal parameters such as morphology and geometry, relatively few studies on performance dependent on external parameters have been reported. In this study, we propose semi-empirical modeling for the performance of membranes as a function of external parameters using a bench-scale pore-filled composite membranes for water vapor separation. As external parameters, we selected temperature, pressure, relative humidity (RH), and feed flow rate. These parameters influence water vapor permeance, water flux, and RH reduction, which are theoretical indicators of the performance of water vapor separation membranes. A power regression analysis was used to find the power of individual parameters (Y = Coefficient (k) ∙ Xpower), and a multiple linear regression analysis (finite power law model, Y = k ∙ X1α ∙ X2β…) was used to develop a semi-empirical model with the correlations of these parameters. The modeling values closely coincided with measured values, suggesting the effectiveness of the proposed modeling. This method is expected to simplify the prediction of membrane performance, offering valuable insights for potential scale-up processes.

A highly water-selective carboxymethylated cellulose nanofiber (CNF-CMC) membrane for the separation of binary (water/N2) and ternary (water/alcohols/N2) systems in vapor-permeation

A separation top layer was successfully deposited using cellulose nanofiber (CNF) and carboxymethylated cellulose nanofiber (CNF-CMC) on a cellulose acetate (CA) microfiltration membrane via the casting method since the filtration method resulted in the penetration of the coating solution into the membrane support. The CNF-CMC-based separation top layer displayed a uniform non-porous structure with a thickness of approximately 1.3 μm thus indicating that most of the membrane pore substrate was covered by CNF-CMC. In contrast, the CNF-based membrane exhibited a non-uniform porous structure within the range of 10–50 nm formed by aggregated CNFs, which is unsuitable for water vapor separation. The CNF-CMC membrane fabricated by the casting method exhibited a high water vapor permeation and H2O/N2 separation factor of 1.6 × 10−6 mol/(m2 s Pa) and 490, respectively, owing to the high dispersibility of the CNF-CMC solutions along with a reduction of macrovoids and microvoids. In ternary separation systems consisting of H2O/alcohols/N2 mixtures, the rich phase of carboxylate groups on the CNF-CMC enhanced the preferential sorption behavior of water vapor while preventing the permeation of isopropyl alcohol (IPA) and N2. The highest separation performance was observed in an H2O/IPA/N2 mixture with a high water vapor permeance level of 1.5 × 10−6 mol/(m2 s Pa) and an H2O/IPA permeance ratio exceeding 79,000.

A super liquid-repellent hierarchical porous membrane for enhanced membrane distillation

Membrane distillation (MD) is an emerging desalination technology that exploits phase change to separate water vapor from saline based on low-grade energy. As MD membranes come into contact with saline for days or weeks during desalination, membrane pores have to be sufficiently small (typically <0.2 µm) to avoid saline wetting into the membrane. However, in order to achieve high distillation flux, the pore size should be large enough to maximize transmembrane vapor transfer. These conflicting requirements of pore geometry pose a challenge to membrane design and currently hinder broader applications of MD. To address this fundamental challenge, we developed a super liquid-repellent membrane with hierarchical porous structures by coating a polysiloxane nanofilament network on a commercial micro-porous polyethersulfone membrane matrix. The fluorine-free nanofilament coating effectively prevents membrane wetting under high hydrostatic pressure (>11.5 bar) without compromising vapor transport. With large inner micro-porous structures, the nanofilament-coated membrane improves the distillation flux by up to 60% over the widely used commercially available membranes, while showing excellent salt rejection and operating stability. Our approach will allow the fabrication of high-performance composite membranes with multi-scale porous structures that have wide-ranging applications beyond desalination, such as in cleaning wastewater.

Gas dehumidification over supported nicotine-based ionic liquid membranes: Effect of alkyl chain length and ether group presence

In this work, supported nicotine-based IL membranes were synthesized and the effect of alkyl chain length and ether groups presence was examined on physicochemical as well as gas and water vapor separation properties. Gas permeation is mainly affected by diffusion, while solubility is the main factor for water vapor permeation. For this reason, alkyl chain lengthening contributed to the increase of all gas (CO2, CH4, N2) permeabilities due to IL viscosity reduction, while water vapor permeability decreased because of the concomitant increase in hydrophobicity. On the other hand, the membrane containing IL with ether groups exhibited the highest water vapor permeability of 141,000 Barrer with a H2O/CH4 selectivity of 126,000 and a H2O/N2 selectivity of 117,000. These permeation properties, which are the highest relative to other reported SILMs with TFSI- as counter anion, remained unchanged even under mixed gas/water vapor conditions, showing the potential for dehumidification processes.

Permeation Properties of Water Vapor through Graphene Oxide/Polymer Substrate Composite Membranes.

Graphene oxide (GO) has attracted attention as an excellent membrane material for water treatment and desalination owing to its high mechanical strength, hydrophilicity, and permeability. In this study, composite membranes were prepared by coating GO on various polymeric porous substrates (polyethersulfone, cellulose ester, and polytetrafluoroethylene) using suction filtration and casting methods. The composite membranes were used for dehumidification, that is, water vapor separation in the gas phase. GO layers were successfully prepared via filtration rather than casting, irrespective of the type of polymeric substrate used. The dehumidification composite membranes with a GO layer thickness of less than 100 nm showed a water permeance greater than 1.0 × 10-6 mol/(m2 s Pa) and a H2O/N2 separation factor higher than 104 at 25 °C and 90-100% humidity. The GO composite membranes were fabricated in a reproducible manner and showed stable performance as a function of time. Furthermore, the membranes maintained high permeance and selectivity at 80°C, indicating that it is useful as a water vapor separation membrane.

A molecular level based parametric study of transport behavior in different polymer composite membranes for water vapor separation

The membrane dehumidification technology has great energy-saving potential compared to traditional methods. However, the design of composite membrane depends mostly on trial tests. To understand the mechanisms dominating material properties and quantitatively predict the air dehumidification performance of the composite membranes in practical applications, various models combined with different polymeric materials and porous support membranes were developed and investigated by using grand canonical Monte Carlo (GCMC) and Molecular dynamics (MD) simulation methods. The interfacial interactions between the selective layer and the support membrane were analyzed in detail to explore the interface stability and compatibility of various composite membranes. The physical characteristics (density, fractional free volume, solubility parameter and cohesive energy density) and transport properties (solubility, diffusivity, permeability and selectivity) of various composite membranes were parametrically evaluated. The polydimethylsiloxane (PDMS) composite membranes exhibited stronger interfacial interaction in comparison to the PVA composite membranes. The hydrophilicity and polarity of polyvinyl alcohol (PVA) polymer resulted in a stronger interaction between the gas molecules and the PVA membrane. According to the solution–diffusion mechanism, the PVA-PVDF membrane presented the optimal H2O permeability of 3121.38 Barrer among all composite membranes. Generally, polyvinylidene fluoride (PVDF) or polyacrylonitrile (PAN) as the materials of support membrane had good fiber forming characteristics and low gas diffusion resistance, which significantly affects the performance of selective layers. The microscopic mechanisms revealed in this work would lay a solid theoretical foundation for the design of high performance composite membrane for air dehumidification.

Reactive Distillation of Glycolic Acid Using Heterogeneous Catalysts: Experimental Studies and Process Simulation.

The glycerol oxidation reaction was developed leading to selective catalysts and optimum conditions for the production of carboxylic acids such as glycolic acid. However, carboxylic acids are produced in highly diluted mixtures, challenging the recovery and purification, and resulting in high production costs, polymerization, and thermal degradation of some of the products. The protection of the acid function by esterification reaction is one of the most promising alternatives through reactive distillation (RD); this technique allows simultaneously the recovery of carboxylic acids and the elimination of most part of the water. The reactive distillation, experimental and simulation, of glycolic acid was performed, based on kinetic and thermodynamic models developed. For the thermodynamic model, binary parameters of the missing couples were determined experimentally, and the non-random two-liquid (NRTL) model was selected as the most suitable to represent the binary behavior. The kinetic study of the esterification in the presence of homogeneous and heterogeneous catalysis concluded that the heterogeneous reaction can be accurately described either by a pseudo-homogeneous model or the Langmuir–Hinshelwood (L-H) adsorption model. Reactive distillation was conducted in a distillation column filled with random packing sulfonated ion-exchange resin, Nafion NR50®, or with extruded TiO2-Wox. The conversion rate of glycolic acid in reactive distillation increases from 14% without catalyst to 30% and 36% using Nafion NR50® and TiO2-Wox, respectively. As opposed to the batch reactor study, the conversion rate of glycolic acid was better with TiO2-Wox than with sulfonated ion-exchange resin. The better performance was related to an increase in the hydrodynamics inside the column. Tests using water in the feed confirm the hypothesis by increasing the conversion rate because of the decrease in the mass transfer resistance by reducing the average diffusion coefficient. The simulation of the reactive distillation column with ProSim® Plus showed that the yield of the ester increased operating at a low feed rate with reactive stripping. In the presence of water in the feed, nonreactive stages are required, including an enrichment region to separate water vapor.

Performance assessment of a flat-sheet membrane-based dehumidifier with serpentine flow channels: An experimental study

Membrane-based dehumidification system is an emerging technology which drives based on the renewable low-grade energy sources. Water vapor selective membrane is able to separate water vapor from the air which can be used to condition air in buildings, more efficiently than conventional air-conditioning equipment. Flow channel designs (especially serpentine-type) and their impacts on the thermal–hydraulic performance of membrane-based dehumidifiers are essential and not well-studied. In the present work, a novel flat-sheet membrane dehumidifier with serpentine flow channels is designed and evaluated experimentally. The serpentine flow channel offers a long flow path that the air in the wet and dry sides of the channel interacts with each other through the membrane, thereby improving the heat and water vapor transfer. The effect of inlet air flow rate, relative humidity, and temperature of both wet and dry sides on the dehumidification rate, approach temperature, pressure drop, and coefficient of performance of the dehumidifier is examined. Results show that passing the humid air with higher flow rate, humidity, and temperature through the wet side channel leads to the higher dehumidification rate, approach temperature, and pressure drop. Increase of wet side air temperature and flow rate enhances the coefficient of performance, and the effect of inlet air relative humidity on the coefficient of performance is observed negligible at high air flow rates. Parametric study of dry side air condition reveals that the air with lower humidity improves the dehumidification rate and coefficient of performance, while its effect on the approach temperature and pressure drop is observed negligible. Elevated air temperature of dry side has positive and negative impact on the approach temperature and coefficient of performance of the dehumidifier, respectively.

Ultrathin double network-coated hollow fiber membrane designed for water vapor separation

Here we present, for the first time, ultrathin double network (DN)-coated hollow fiber membranes to improve water vapor permeation of polymeric membranes. In this study, we investigated two different DN systems. The hyperbranched polyethyleneimine (HPEI) and its quaternized HPEI form (QHPEI) represented the first network in both systems, while the second network was based on quaternized polyacrylic acid (QACC) and quaternized poly (2-acrylamido-2-methyl-1-propanesulfonic acid) (QAMPS). Various analysis techniques were used to characterize QHPEI and DN-coated polysulfone (PSf) membranes. Water vapor permeation experiments were conducted at QHPEI concentration in total precursor (QHPEI and HPEI) and different operating parameters. The incorporation of a higher QHPEI amount improved the hydrophilicity and water vapor performance of DN-coated membranes. QAAC-100 and QAMPS-100 exhibited the highest performance in each system; however, QAMPS showed higher water vapor permeance (P) and lower selectivity (S). This behavior was attributed to the presence of a bulkier pendant group (i.e. less compact), higher hydrophilicity, and a thinner membrane in QAMPS compared to QAAC. The increment in relative humidity (RH) illustrated a positive effect on the membrane performance, while both temperature and pressure illustrated a negative impact. The best performance obtained by QAAC-100 (S = 511, P = 5825 GPU) and QAMPS-100 (S = 422, P = 8115 GPU) was achieved at 1 bar as feed pressure, 75% as RH, 35 °C as operating temperature, and 1 L/min as feed gas flow rate.

Molecular simulation of enhanced separation of humid air components using GO-PVA nanocomposite membranes under differential pressures.

Hydrophilic nanocomposite membranes have significant advantages in the separation of water vapor which is the core process in air dehumidification. This paper focuses on exploring the micro-mechanism of enhanced separation using graphene oxide-polyvinyl alcohol (GO-PVA) nanocomposite membranes. The sorption and diffusion behaviors of water vapor and nitrogen in GO-PVA membranes were investigated using molecular dynamics (MD) and Monte Carlo (MC) methods. The study showed that embedding GO into a PVA matrix results in a higher glass transition temperature and fractional free volume. The latter is believed to enhance the diffusivity of gas molecules in polymeric membranes. The interaction between the polymer chains and GO nanoparticles notably promotes the adsorption capacity of water vapor and inhibits nitrogen adsorption in the membrane. A water vapor permeance of 8844.07 Barrer and a separation factor of 3.53 could be achieved with the GO-PVA-0.5 membrane. The analysis confirmed that GO has the same effect on single gas and binary gas mixtures, i.e., increasing the water vapor permeability and selectivity. The calculated water vapor permeance of binary gas is 83% lower than that of single gas permeation. It is expected that this research could provide fundamentals for the optimization and synthesis of gas separation membranes.

Synthesis and properties of Polymeric ionic liquids (PILs) bearing hydrophilic PEO groups: Evaluation of gas and water vapor separation performance

New pyridinium based PILs containing PEO pendants were synthesized to be examined as CO2 and water selective membranes. A two-step synthetic procedure was followed including an N-methylation reaction of a precursor copolymer and a subsequent anion exchange metathesis to afford the corresponding PILs. The prepared PILs having different counter-anions form mechanically robust, flexible membranes, which exhibit high thermal stability and Tgs close to room temperature. It was examined the effect of anion nature on physicochemical as well as gas/water vapor separation properties. The conversion of the precursor copolymer to its corresponding PIL analogues led to Tg increase and thermal stability decrease of the latter. Surprisingly, the gas permeability for all PILs was decreased compared to precursor owing to the strong cation-anion interactions developed in the PIL structures which lead to a tighter polymer chain packing and consequently to gas diffusion hindering. The PIL containing the C(CN)3− anion (PIL750-C(CN)3) experiences the lowest CO2 permeability compared to TFSI− and MeSO4− which is accompanied by a very high CO2/CH4 selectivity value of 70 that is among the highest reported in the literature for PILs. This behavior can be attributed to its dense polymer chain packing and thus to its strong sieve-sieving ability associated with the diffusion-driven permeability decrease. Regarding water vapor permeability, it was evidenced that the PIL containing the MeSO4− anion (PIL750-MeSO4) showed the highest water vapor permeability (80,000 Barrer) compared to anions TFSI− and C(CN)3−, which is attributed to MeSO4− increased hydrophilicity and higher hydrogen bond basicity. The high water permeability is accompanied by a very high H2O/CO2 and H2O/N2 selectivity. The water vapor effect on gas permeation of PIL750-TFSI and PIL750-MeSO4 under process gas streams conditions using two different mixtures with compositions 3% H2O:14.5% CO2:82.5 %N2 and 3% H2O:48.5% CO2:48.5% CH4, respectively, was also investigated. The results demonstrate that gas permeability of all tested gases increased under humid conditions due to plasticization induced by water vapor. Accordingly, the separation factors decreased when compared with ideal selectivities in dry conditions for both PILs. However, PIL750-MeSO4 combines the high water vapor permeability with the high H2O/CO2 and HO2/N2 separator factors highlighting its potential to be used in flue gas dehydration and air dehydration.

Numerical Simulation of the Water Vapor Separation of a Moisture-Selective Hollow-Fiber Membrane for the Application in Wood Drying Processes.

In this study, a simplified two-dimensional axisymmetric finite element analysis (FEA) model was developed, using COMSOL Multiphysics® software, to simulate the water vapor separation in a moisture-selective hollow-fiber membrane for the application of air dehumidification in wood drying processes. The membrane material was dense polydimethylsiloxane (PDMS). A single hollow fiber membrane was modelled. The mass and momentum transfer equations were simultaneously solved to compute the water vapor concentration profile in the single hollow fiber membrane. A water vapor removal experiment was conducted by using a lab-scale PDMS hollow fiber membrane module operated at constant temperature of 35 °C. Three operation parameters of air flow rate, vacuum pressure, and initial relative humidity (RH) were set at different levels. The final RH of dehydrated air was collected and converted to water vapor concentration to validate simulated results. The simulated results were fairly consistent with the experimental data. Both experimental and simulated results revealed that the water vapor removal efficiency of the membrane system was affected by air velocity and vacuum pressure. A high water vapor removal performance was achieved at a slow air velocity and high vacuum pressure. Subsequently, the correlation of Sherwood (Sh)–Reynolds (Re)–Schmidt (Sc) numbers of the PDMS membrane was established using the validated model, which is applicable at a constant temperature of 35 °C and vacuum pressure of 77.9 kPa. This study delivers an insight into the mass transport in the moisture-selective dense PDMS hollow fiber membrane-based air dehumidification process, with the aims of providing a useful reference to the scale-up design, process optimization and module development using hollow fiber membrane materials.

A New Device Hypothesis for Water Extraction from Air and Basic Air Condition System in Developing Countries

This work proposes a new device for air treatment with dehumidification and water recovery/storage, with possible mitigation of indoor environmental conditions. The system is based on Peltier cells coupled with a horizontal earth-to-air heat exchanger, it is proposed as an easy-to-implement alternative to the heat pumps and air handling units currently used on the market, in terms of cost, ease of installation, and maintenance. The process provides the water collection from the cooling of warm-humid air through a process that leads to condensation and water vapor separation. The airflow generated by a fan splits into two dual flows that lap the two surfaces of the Peltier cells, one flow laps the cold surfaces undergoing sensible, latent cooling with dehumidification; the other flow laps the hot surfaces and heats up. The airflow undergoes thermal pre-treatment through the underground horizontal geothermal pipe that precedes the Peltier cells. In the water storage tank, which also works as a mixing chamber, the two air streams are mixed to regulate the outlet temperature. The system can be stand-alone if equipped with a photovoltaic panel and a micro wind turbine, able to be used in places where electricity is absent. The system, with different configurations, is modeled in the African city Kigali, in Rwanda.

Air dehumidification using various TEG based nano solvents in hollow fiber membrane contactors

In this study, tri-ethylene glycol (TEG) based nanofluids of carbon nanotubes (CNT), silica (SiO2) and aluminum oxide (Al2O3) in different weight percents of 0.01 and 0.05 wt% were employed to improve the properties of TEG for water vapor absorption in a hollow fiber membrane contactor (HFMC). To do so, the impact of various operational parameters including nanofluid type, nanoparticles (NPs) concentration, liquid and gas flow rate on water vapor separation were elucidated. According to obtained results, CNT nanofluid was more capable on water vapor absorption toward SiO2 and Al2O3, so that the injection of CNT nanofluid led to water vapor absorption enhancement up to 10.8 % as compared to TEG solution alone. The results also indicated that the gas flow rate has an inverse relationship with the amount of water vapor absorption efficiency, whereas increasing the liquid flow rate has no tangible effect on absorption efficiency, which is because of the very high solubility of water vapor in TEG. Ultimately, dynamic light scattering (DLS) analysis was carried out to evaluate the stability of nanofluids and size distribution of nanostructures in the base fluid.

Recent progress and prospects of polymeric hollow fiber membranes for gas application, water vapor separation and particulate matter removal

High-performance hollow fiber membranes can be produced through proper tailoring of spinning parameters.

Solar-thermal membrane for dewatering aqueous organic-acid solutions

A thermally conductive porous membrane has been developed to directly absorb solar energy and conduct heat that can effectively evaporate liquid water at the interface between the membrane and the bulk feed solution. Black, porous, thermally conductive graphite foam support is employed as an effective photothermal-energy absorber and heat conductor that heats up an aqueous feed solution to produce vapor. Graphite nanoparticle-slurry coating is applied onto the foam surface to reduce the pore size and generate a microporous membrane. Then, application of a dense graphene oxide membrane coating as an active separation layer on the microporous nanoparticle surface of internal foam channels allows vapor permeation of volatile molecules. Acetic acid/water solution was studied as a model feed system to experimentally demonstrate effective separation. This model vapor permeation system demonstrates excellent acetic acid separation, with a separation factor of 8.3, under simulated 0.7 sun irradiation. The membrane hydrophobicity and nanostructure, including pore size and surface chemistry, played a significant role in enabling high permselectivity of water vapor over acetic acid molecules, as well as liquid solution. Pore size reduction from open pores to a nonporous dense layer in the membrane enables effective separation of water vapor from the organic vapor, while it reduces the permeation flux. Also, the hydrophilicity of the membrane surface shows ∼3 times higher permeation flux with higher permselectivity, compared with the hydrophobic membrane surface. This work introduces a process of directly using renewable energy instead of conventional heating to drive selective separation of water from organic acids.

A new perspective of functionalized MWCNT incorporated thin film nanocomposite hollow fiber membranes for the separation of various gases

As the increasing demand for gas separation technologies in the industry, the polymeric membrane separation technology has received wide attention based on the advantages of high gas permeance, and low cost. Thin film nanocomposite (TFN) membranes used for the gas separation in industrial level is one of the best choices, because of applied nanoparticles synergistic properties influence to enhance gas permeance and selectivity. In this study thin selective nanocomposite layer has been developed using interfacial polymerization between 3,5-diaminobenzoic acid (DABA) with carboxylated multi-walled carbon nanotubes (C-MWCNTs) and trimesoyl chloride (TMC) on the surface of polysulfone hollow fiber substrate for the separation of various gases like water vapor, H2, CO2, CH4 and N2. Different concentrations of C-MWCNTs are used for the preparation of various TFN membranes. All prepared TFN membranes were well characterized using different physiochemical characterization techniques like ATR-FTIR, AFM, SEM, XPS, contact angle etc. It is found that the prepared membranes are not only used for the separation of water vapor but also utilize for the separation of different gases like H2, CO2, CH4, and N2. The TFN hollow fiber membranes prepared with 0.04 % C-MWCNTs, (C-MWCNT@DT-M4) show good performance in the form of permeance and selectivity among all the prepared membranes, as a water vapor permeance 2570 GPU, H2 permeance 92.5 GPU, along with the water vapor/N2 641, H2/CO2 4.41 and CO2/N2 24.74 and CO2/CH4 18.45 selectivities respectively. The prepared TFN membranes show superior performance to C-MWCNT-based membranes because of their synergetic bonding chemistry and hydrophilic nature. This study has proven that slight addition of functional MWCNTs in polymeric nanocomposite membranes responsible to obtain better performance of the TFN membranes.

Role of polymeric calcium-alginate particles to enhance the performance capabilities of composite membranes for water vapor separation

We synthesized polymeric calcium-alginate (CA) particles with an “egg box” structure using an emulsification additive process to enhance the performance of the thin film composite (TFC) membranes for water vapor separation. The appealing feature of CA particles is that they have a variety of hydrophilic groups, such as hydroxyl and carboxyl groups, which allow them to absorb more water vapor at a relatively rapid rate. Moreover, CA particles are readily available, inexpensive, and biocompatible. Moreover, they can be obtained by one-pot synthesis, which is a relatively simple and convenient method. These particles can be characterized with different techniques. Transmission electron microscopy (TEM) mapping data and X-ray photoelectron spectroscopy (XPS) data illustrate fundamentally that CA particles consist of mostly calcium and oxygen. Energy dispersive X-ray (EDX) data show that the calcium rises from 0 to 0.41 atomic percent when CA content increases from 0.0 to 0.35 wt%. Water vapor/nitrogen gas permeation results show that relatively more CA particles in the polyamide (PA) layer increases the water vapor permeation due to the increased number of sorption sites and greater surface area provided by the particles with their many hydrophilic functional groups. The TFC membrane with 0.1 wt% CA loading shows the best performance such as water vapor permeance of 2143 GPU and selectivity of 706. Thus, adding a small amount of polymeric CA particles to a PA layer can enhance the performance of TFC membranes, making them a viable candidate for water vapor separation membranes.