Mixed Membranes Research Articles

Preparation of TA-O-MoS2/PES mixed matrix ultrafiltration membrane for rare earth wastewater treatment

The trade-off between permeability and selectivity, along with the issue of membrane fouling, has constrained the widespread application of ultrafiltration (UF) membranes in recycling rare earth wastewater. Here, we present the incorporation of tannic acid (TA) modified molybdenum disulfide oxide (O-MoS2) as a functional enhancer to fabricate polyethersulfone (PES) based mixed matrix membranes through a nonsolvent induced phase separation (NIPS) approach. Compared to the unmodified PES membrane, the integration of TA-O-MoS2 significantly improves the hydrophilicity, porosity in the mixed matrix membrane. By altering the concentration of TA-O-MoS2, the TA-O-MoS2/PES UF membrane achieves enhanced hydrophilicity and charge properties, resulting in a remarkable improvement in separation performance. Specifically, the optimized membrane M2 (TA-O-MoS2 addition of 0.1 wt%) exhibits a water flux of 140.98 Lm−2h−1bar−1 and a PEG 20000 rejection rate of 91.00 %, representing increases of 180 % and 120 % over the control PES membrane, respectively. Notably, membrane M2 effectively retains 91.31 % of macromolecular organic compounds in rare earth wastewater, while permitting nearly complete passage of inorganic salts, for instance CaCl2 (3.26 %) and MgSO4 (4.84 %). Moreover, the TA-O-MoS2/PES membrane demonstrates robust antifouling properties and exceptional durability, indicating its significant potential for efficient treatment and resource recovery in rare earth wastewater.

Synthetic membrane selection for in vitro release testing (IVRT): A case study of topical mometasone furoate semi-solid dosage forms

In vitro release testing (IVRT) is extensively used to develop the formulation of topical semi-solid products, to evaluate the quality and consistency of the product after scale-up and post-approval changes, and more recently to aid the evaluation of topical generic products’ equivalency. The selection of synthetic membrane is one of the most critical parameters of the method development part of IVRT. It is well known that the membrane features namely its polymer matrices, porosity, pore size, thickness can have a substantial effect on the IVRT data. However, there is no detailed information available in the literature regarding the membrane selection for different types of topical dosage forms. Therefore, we aimed to investigate whether difference topical semi-solid dosage forms of the same drug molecule would cause to variation in the membrane selection. Within this framework, rheological behaviour of commercially available three different types of topical semi-solid dosage forms (ointment, cream, and lotion) of mometasone furoate (0.1%) were primarily characterized. Then, the membrane inertness test was conducted using a series of synthetic hydrophilic membranes (regenerated cellulose, cellulose acetate, cellulose nitrate, mixed cellulose ester membranes) and hydrophobic membranes (polyether sulfone, polypropylene, polytetrafluoroethylene membranes) after identifying of an appropriate receptor medium that ensures sink condition for mometasone furoate. Lastly, IVRT studies from the topical semi-solid products were performed utilizing Franz-type diffusion cells. The membrane inertness and in vitro release data demonstrated that the cellulose acetate membrane showed superior diffusion properties in general while the other synthetic membranes exhibited varying outcomes for different semi-solid dosage forms of mometasone furoate. Overall, the results indicated that the release rate and the cumulative drug released amount of drug after 6 h through the different synthetic membranes might vary depending on the semi-solid dosage form. In order to select the synthetic membrane for IVRT, it should also be considered potential interactions between the polymer matrices and the chemical structure of drug molecule as well as formulation components prior to conducting membrane inertness test and IVRT studies.

Surface treatment optimization of mixed cellulose ester membrane by cold plasma treatment to improve apple juice clarification

This study aimed to determine the optimal conditions for the surface modification of mixed cellulose ester (MCE) microfiltration membrane by cold plasma (CP) for apple juice clarification. Response surface method using central cubic design (CCD) was employed for the optimization of the membrane surface modification process. Plasma gas type (oxygen, carbon dioxide, and air), power (10, 15, and 20 W), and exposure time (120, 180, and 240 s) were used as the factors for cold plasma surface modification. The results revealed the surface modification of the MCE membrane using air as plasma gas with plasma power and exposure time equal to 10 W and 180 s resulted in the maximum permeate flux in apple juice clarification. The results of scanning electron microscope, and atomic force microscope confirm the effect of CP treatment on the membrane surface roughness. Fourier transform infrared spectroscopy showed the incorporation of the hydroxyl group into the membrane surface due to CP treatment which affected the surface contact angle and hydrophilicity. The CP treatment of the membrane significantly affects the membrane resistances. Also, the surface modification of the MCE membrane using the CP treatment process in optimal conditions is an effective method for clarifying apple juice.

Clarification of apple juice using cold plasma treated mixed cellulose esters membrane: flux modeling, membrane fouling, and juice physicochemical properties evaluation

This study aimed to clarify apple juice using unmodified and low-pressure cold plasma (gas: air, power: 10 W, and exposure time: 180 s) surface-modified mixed cellulose esters (MCE) microfiltration membranes. The effect of feed pressure (20, 40, and 60 kPa), feed flow rate (10, 15, and 20 mL/s), and feed temperature (27 and 40°C) on the permeate flux was evaluated using response surface methodology (RSM). The binary interaction of feed pressure and temperature and the second-order (non-linear) interaction of feed pressure and flow rate had a significant effect on the permeate flux (P<0.05). Generally, the process at 60 kPa, 15 mL/s, and 40 °C resulted in the maximum permeate flux. The cold plasma surface modification of the MCE membrane increased the permeate flux by about 45% at the optimum process conditions. Evaluation of membrane fouling showed that the cake formation was the predominant membrane fouling mechanism during both membrane processing. The physicochemical properties evaluation revealed that the surface-modified membrane produced clarified apple juice with antioxidant activity, reducing sugars, total sugars, phenolic, and vitamin C contents about 18.87%, 12.9%, 15.49%, 24.53%, and 45.15% more than clarified apple juice produced with unmodified MCE membrane, respectively.

Fabrication of TiO2@ZIF-67 metal organic framework composite incorporated PVDF membranes for the removal of hazardous reactive black 5 and Congo red dyes from contaminated water

Novel application of TiO2@ZIF-67 composite incorporated poly (vinylidene fluoride) (PVDF) mixed matrix flat-sheet membranes for treating the water contaminated with hazardous reactive black 5 and congored dyes was the crux of this work. The composite was characterized by FTIR, BET, XRD, zeta potential and particle size, and TGA. The as-synthesized composite was embedded in the PVDF polymeric matrix and flat-sheet-membranes were fabricated adopting the NIPS method followed by the different characterizations like scanning electron microscopy, EDS, elemental mapping, contact angle, atomic force microscopy, surface energy, and XPS. Results of the performance studies showed an enhanced pure water permeability from 150.99 Lm-2h−1 for neat membrane to 261.39 Lm-2h−1 for TZM-2. The reactive black 5 dye was rejected in 97.4 %, 92.2 %, and 84.84 % in acidic, basic and neutral conditions respectively by TZM-2 membrane. Whereas, the PVDF membranes without the composite showed rejections of 83.19 %, 82.5 %, and 72.1 % respectively in acidic, basic, and neutral conditions. The Congo Red dye was rejected in 89.4 %, 95.68 %, and 92.4 % in acidic, neutral and basic conditions respectively by TZM-2 membranes. Whereas, the PVDF membranes without the composite showed rejections of 82.8 %, 91.9 %, and 85.4 % respectively in acidic, neutral and basic conditions.

Optimizing Archaeal Lipid Biosynthesis in Escherichia coli.

Membrane lipid chemistry is remarkably different in archaea compared with bacteria and eukaryotes. In the evolutionary context, this is also termed the lipid divide and is reflected by distinct biosynthetic pathways. Contemporary organisms have almost without exception only one type of membrane lipid. During early membrane evolution, mixed membrane stages likely occurred, and it was hypothesized that the instability of such mixtures was the driving force for the lipid divide. To examine the compatibility between archaeal and bacterial lipids, the bacterium Escherichia coli has been engineered to contain both types of lipids with varying success. Only limited production of archaeal lipid archaetidylethanolamine was achieved. Here, we substantially increased its production in E. coli by overexpression of an archaeal phosphatidylserine synthase needed for ethanolamine headgroup attachment. Furthermore, we introduced a synthetic isoprenoid utilization pathway to increase the supply of isopentenyl-diphosphate and dimethylallyl diphosphate. This improved archaeal lipid production substantially. The archaeal phospholipids also served as a substrate for the E. coli cardiolipin synthase, resulting in archaeal and novel hybrid archaeal/bacterial cardiolipin species not seen in living organisms before. Growth of the E. coli strain with the mixed membrane shows an enhanced sensitivity to the inhibitor of fatty acid biosynthesis, cerulenin, indicating a critical dependence of the engineered E. coli strain on its native phospholipids.

Mixed-Matrix Organo-Silica-Hydrotalcite Membrane for CO2 Separation Part 1: Synthesis and Analytical Description.

Hydrotalcite exhibits the capability to adsorb CO2 at elevated temperatures. High surface area and favorable coating properties are essential to harness its potential for practical applications. Stable alcohol-based dispersions are needed for thin film applications of mixed membranes containing hydrotalcite. Currently, producing such dispersions without the need for delamination and dispersing agents is a challenging task. This work introduces, for the first time, a manufacturing approach to overcoming the drawbacks mentioned above. It includes a synthesis of hydrotalcite nanoparticles, followed by agent-free delamination of their layers and final dispersion into alcohol without dispersing agents. Further, the hydrotalcite-derived sorption agent is dispersed in a matrix based on organo-silica gels derived from 1,2-bis(triethoxysilyl)ethane (BTESE). The analytical results indicate that the interconnection between hydrotalcite and BTESE-derived gel occurs via forming a strong hydrogen bonding system between the interlayer species (OH groups, CO32-) of hydrotalcite and oxygen and silanol active gel centers. These findings lay the foundation for applications involving incorporating hydrotalcite-like compounds into silica matrices, ultimately enabling the development of materials with exceptional mass transfer properties. In part 2 of this study, the gas separation performance of the organo-silica and the hydrotalcite-like materials and their combined form will be investigated.

Modulation of Interlayer Nanochannels via the Moderate Heat Treatment of Graphene Oxide Membranes.

In response to the phenomenon of interlayer transport channel swelling caused by the hydration of oxygen-containing functional groups on the GO membrane surface, a moderate heat treatment method was employed to controllably reduce the graphene oxide (GO) membrane and prepare a reduced GO composite nanofiltration membrane (mixed cellulose membrane (MCE)/ethylenediamine (EDA)/reduced GO-X (RGO-X)). The associations of different heat treatment temperatures with the hydrophilicity, interlayer structure, permeability and dye/salt rejection properties of GO membranes were systematically explored. The results indicated that the oxygen-containing groups of the GO membrane were partially eliminated after heat treatment, and the hydrophilicity was weakened. This effectively weakened the hydration between the GO membrane and the water molecules and inhibited the swelling of the oxidized graphene membrane. In the dye desalination test, the MCE/EDA/RGO membrane exhibited an ultra-high rejection rate of over 97% for methylene blue (MB) dye molecules. In addition, heat treatment increased the structural defects of the GO membrane and promoted the fast passage of water molecules via the membrane. In pure water flux testing, the water flux of the membrane remained above 46.58 Lm-2h-1bar-1, while the salt rejection rate was relatively low.

Band gap engineering of g-C3N4/CuS and its application in Solar Still

Interfacial solar steam generation is considered as economical and more effective implementation of Solar steam generation (SSG) where solar energy is concentrated at the liquid surface via the utilization of heat localization materials (HLM). Herein we report the fabrication of an HLM constituted of a nanocomposite absorber of graphitic carbon nitride (g-C3N4) and covellite copper sulfide (CuS) supported on a mixed cellulose ester membrane, with a substrate of air laid paper-wrapped polystyrene foam. This structure allowed for strong broad-spectrum absorbance, increased hydrophilic character and minimal thermal losses. The HLM system absorbed 98% of the material and had an evaporation rate of 2.58 kgs per square meter per hour. This is twice the evaporation rate of water tested under the same conditions. Moreover, as fabricated HLM was also incorporated in a solar still in order to assess its practical performance in solar distillation. Initial studies proved that HLM modified solar still was more effective than conventional solar stills.

Enhancement in performance of the PVC/nanoclay mixed matrix nanofiltration membrane

Enhancement in performance of the PVC/nanoclay mixed matrix nanofiltration membrane

Enhanced permeability and antifouling properties of carboxylated polysulfone/quaternized polyimide blend ultrafiltration membrane

AbstractThe intricate interplay between chemical composition and the incorporation of functional fillers plays a pivotal role in shaping the structural attributes and separation efficacy of mixed matrix ultrafiltration membranes. In this work, we report the utilization of a novel organic filler of hydrophilic modified polyimide particles (PI‐SO3) for the first time in the preparation of mixed matrix ultrafiltration membranes. A series of ultrafiltration membranes were fabricated using polysulfone as the matrix material and PI‐SO3 as the additive. The addition of PI‐SO3 to the mixed matrix membrane effectively enhanced both water flux and antifouling ability. The ultrafiltration membrane with 0.2% particle content exhibited the highest pure water flux at 535.5 L h−1 m−2, owing to the synergistic regulation of pore structures and surface hydrophilicity. The ultrafiltration membrane with 0.5% PI‐SO3 particles demonstrated the highest flux recovery rate at 76.8%, attributed to the superior hydrophilicity displayed by the added particles within the ultrafiltration membrane. The increased particles content correlated with improved hydrophilicity on the membrane surface, resulting in enhanced antifouling performance. The hydrophilic modified particles effectively regulated pore structures, surface hydrophilicity, and surface charge, ultimately enhancing the performance of mixed matrix ultrafiltration membranes for wastewater purification. Therefore, the use of modified polyimide particles as fillers introduces an innovative method to economically enhance ultrafiltration membranes, providing a potential solution to mitigate the economic costs associated with trade‐off effects during the modification process.

Heavy metals remediation using MOF5@GO composite incorporated mixed matrix ultrafiltration membrane

A polysulfone-based mixed matrix membrane (MMM) was prepared by incorporation of MOF5@GO composite in the polymer matrix. The prepared membrane was characterized by permeability, scanning electron microscopy, Fourier transform infrared spectroscopy, zeta potential, X-ray photoelectron spectroscopy, atomic force microscope, molecular weight cut-off and average pore radius. MMM exhibits enhanced permeability, pore size, surface roughness and molecular weight cut-off compared to polysulfone membrane. Pure water permeability of M−0.5 enhanced from 37.9 to 59.5 L/m2h.bar, which corroborated an increase in molecular weight cut-off from 46.9 to 74.1 kDa and pore radius from 66.9 to 75.4 Å as MOF5@GO composite was incorporated in polysulfone polymer matrix. At neutral pH, the optimized MMM (M−0.5) shows –22.7 mV zeta potential facilitating the adsorption of heavy metals. The M−0.5 membrane exhibits 95–99 % rejection of Pb, Cu, Zn and Cd at 2 bar pressure with enhanced permeate flux (∼116 L/m2h) compared to the polysulfone membrane. M−0.5 membrane shows better antifouling properties than the polysulfone membrane. Among the heavy metals studied, lead and copper showed the maximum rejection. The MMM shows 99 % rejection of lead and copper and breakthrough time of 12 and 9 h, respectively for a small membrane area (0.0012 m2). Thus, the prepared low-pressure driven mixed matrix ultrafiltration membrane was suitable and competent for heavy metal rejection. A modified convection-adsorption model based on the first principle was used to predict the long-term filtration performance of the membrane. The same model was used to generate the performance curve for scaling up the process.

Gramicidin A as a mechanical sensor for mixed nonideal lipid membranes.

Gramicidin A (gA) is a short hydrophobic β-helical peptide that forms cation-selective channels in lipid membranes in the course of transbilayer dimerization. The length of the gA helix is smaller than the thickness of a typical lipid monolayer. Consequently, elastic deformations of the membrane arise in the configurations of gA monomers, conducting dimer, and the intermediate state of coaxial pair, where gA monomers from opposing membrane monolayers are located one on top of the other. The gA channel is characterized by the average lifetime of the conducting state. The elastic properties of the membrane influence the average lifetime, thus making gA a convenient sensor of membrane elasticity. However, the utilization of gA to investigate the elastic properties of mixed membranes comprising two or more components frequently relies on the assumption of ideality, namely that the elastic parameters of mixed-lipid bilayers depend linearly on the concentrations of the components. Here, we developed a general approach that does not rely on the aforementioned assumption. Instead, we explicitly accounted for the possibility of inhomogeneous lateral distribution of all lipid components, as well as for membrane-mediated lateral interactions of gA monomers, dimer, coaxial pair, and minor lipid components. This approach enabled us to derive unknown elastic parameters of lipid monolayer from experimentally determined lifetimes of gA channel in mixed-lipid bilayers. A general algorithm was formulated that allows the unknown elastic parameters of a lipid monolayer to be obtained using gA as a mechanical sensor.

One-step facile fabrication of PDA@MCE for high efficiency seawater desalination

A variety of photothermal materials have been developed and applied in photothermal seawater desalination. As a conjugated polymer, Polydopamine (PDA) has excellent light absorption properties in the UV–visible region, and is widely used as a solar energy material. In this work, Polydopamine-mixed cellulose membrane (PDA@MCE) with Janus structure was prepared by a one-step method for water evaporation at the interface between PDA and mixed cellulose membrane (MCE). PDA@MCE has good thermal stability. When the reaction time is 6 h, the evaporation rate of the composite is twice that of MCE, and the photothermal conversion efficiency is about 62 %. PDA@MCE, as a kind of photothermal material with simple preparation method and friendly to the environment, has excellent application potential in solar driven interfacial water evaporation.

Cellulose acetate, a source from discarded cigarette butts for the development of mixed matrix loose nanofiltration membranes for selective separation

This study presents an environmentally friendly method for extracting cellulose acetate (CA) from discarded cigarette filters, which is then utilized in the fabrication of cellulose-based membranes designed for high flux and rejection rates. CA membranes are likeable to separate dyes and ions, but their separation efficiency is exposed when the contaminant concentration is very low. So, we have integrated graphene oxide (GO) and carboxylated titanium dioxide (COOH-TiO2) in CA to develop mixed matrix membranes (MMMs) and studied them against dyes and most used salts. The CA has been extracted from these butts and added GO and COOH-TiO2 nanoparticles to develop MMMs. The present work administers the effective separation of five dyes (methyl orange, methyl violet, methylene blue, cresol red, and malachite green) and salts (NaCl and Na2SO4) along with the high efficiency of water flux by prepared CA membranes. The prepared membranes rejected up to 94.94 % methyl violet, 91.28 % methyl orange, 88.28 % methylene blue, 89.91 % cresol red, and 91.70 % malachite green dye. Along with the dyes, the membranes showed ∼40.40 % and ∼ 42.97 % rejection of NaCl and Na2SO4 salts, respectively. Additionally, these membranes have tensile strength up to 1.54 MPa. Various characterization techniques were performed on all prepared CA membranes to comprehend their behaviour. The antibacterial activity of MMMs was investigated using the Muller-Hinton-Disk diffusion method against the gram-positive bacterium Staphylococcus aureus (S. aureus) and the gram-negative bacterium Escherichia coli (E. coli). We believe the present work is an approach to utilizing waste materials into valuable products for environmental care.

A fast and effective way to measure the inner pore size distributions of wetted cotton fibers and their pretreatment performance using time-domain nuclear magnetic resonance

This study reports the findings from using time-domain nuclear magnetic resonance (TD-NMR) to analyze the pore structures of cotton fibers. Cotton fibers, which swell and soften in water, present challenges for conventional pore measurement techniques. TD-NMR overcomes these by measuring the transverse relaxation time (T2) of water protons within the fibers, indicative of internal pore sizes. We established a T2-to-pore size conversion equation using mixed cellulose ester membranes. This enabled differentiation between strongly bound, loosely bound, and free water within the fibers, and detailed the water distribution. A method for measuring the pore size distribution of wet cotton fiber was developed using TD-NMR. We then examined how various pretreatments affect the fibers' internal pores by comparing their pore size distribution and porosity. Specifically, caustic mercerization primarily enlarges the porosity and size of larger pores, while liquid ammonia treatment increases porosity but reduces the size of smaller pores. This research confirms TD-NMR's utility in assessing cotton fabrics' wet processing performance.

Mesoporous Mg–Al–Ti composite oxide incorporated mixed matrix ultrafiltration membrane with superior multi-heavy metal removal capacity, anti-fouling & anti-microbial property

Mesoporous Mg–Al–Ti ternary composite oxide nano-adsorbents have demonstrated an exceptional performance to remove multiple heavy metals (As, Pb, Cd, Cr). Incorporation of these nanoparticles (NPs) in polysulfone membrane created a multifunctional mixed matrix membrane (MMM) with heavy metal adsorption capacity (both cationic and anionic species), enhanced hydrophilicity, anti-fouling property, and anti-microbial activity. The best heavy metal removal performance was shown by the membrane incorporated with 0.8 wt% NPs. Hydrophilicity improvement was studied through the decrease in water contact angle from 71° to 57° and surface probing using atomic force microscopy (AFM). With a maximum As(III) adsorption capacity of 256.6 mg/g, the membrane had a breakthrough volume of 25L and could provide safe drinking water for 19 h from a real Arsenic (As) contaminated groundwater sample with a flux of 48 l/m2-h. Beyond that, >90 % removal of Cd, Pb & Cr was also observed with maximum adsorption capacity of 652.9 mg/g, 332.5 mg/g, and 89.4 mg/g respectively. 92.5 % flux recovery after filtering a 1000 ppm bovine serum albumin showed the anti-fouling property. Successful inhibition of both gram-positive and gram-negative bacterial growth, and >99.99 % removal of colony forming units (CFU/ml) in the filtration process confirmed the anti-microbial resistance. With its multifunctionality, these membranes hold great potential for practical water treatment applications.

Interaction of L-phenylalanine with carbonyl groups in mixed lipid membranes

The interaction of L-Phe with the membrane components, i.e., lipids and proteins, has been discussed in the current literature due to the interest to understand the effect of single amino acids in relation to the formation of amyloid aggregates.In the present work, it is shown that L-Phe interacts with 9:1 DMPC (1,2-dimyristoyl-sn-glycero-3 phosphocholine)/DPPC (1,2-dipalmitoyl-sn-glycero-3 phosphocholine) mixtures but not in the 1:9 one. An important observation is that the interaction disappears when DPPC is replaced by diether PC (2-di-O-hexadecyl-sn-glycero-3-phosphocholine) a lipid lacking carbonyl groups (CO). This denotes that CO groups may interact specifically with L-Phe in accordance with the appearance of a new peak observed by Infrared spectroscopy (FTIR-ATR). The interaction of L-Phe affects the compressibility pattern of the 9:1 DMPC/DPPC mixture which is congruent with the changes observed by Raman spectra.The specific interaction of L-Phe with CO, propagates to phosphate and choline groups in this particular mixture as analyzed by FTIR-ATR spectroscopy and is absent when DMPC is dopped with diether PC.

MXene/Ag3PO4 modified PVDF composite membranes for efficient interfacial evaporation and photodegradation

Solar-powered interface evaporation is considered a promising technology to obtain freshwater from non-potable water by using sustainable solar energy. However, research on combining the photocatalytic effect with solar interfacial evaporation technology to go for photothermal conversion materials with full solar spectrum utilization for photothermal and photodegradation capabilities is still scarce. Due to the unique optical properties of MXene, a novel MXene/Ag3PO4-based membrane with synergistic photothermal and photocatalytic effects was developed from the perspective of practical applications such as water purification, photodegradation of organic dyes and antibacterial properties. In this paper, polyvinylidene fluoride (PVDF) and carbon black (CB) were used as the substrate, calcium carbonate (CaCO3) and hydrochloric acid (HCl) were selected as the pore-forming agent for hydrophilic modification, and MXene/Ag3PO4 serves as the photocatalyst. The prepared composite polyvinylidene fluoride membrane (PCC-MXene/Ag3PO4) with Schottky junction, possesses a rich pore structure, abundant water molecule transport channels, high light absorption ability, and low thermal conductivity, which lead to a good performance in solar interface evaporation, photodegradation and antibacterial. The superhydrophobicity and floatability of the nanosponges in water enable them to continuously pump water, which greatly promotes the dissolution of salt accumulation. With the help of porous nanosponges, PCC-MXene/Ag3PO4 exhibits excellent evaporation stability and salt resistance under 1 kW m−2 solar irradiation, as well as photodegradation of organic dyes. In addition, the PCC-MXene/Ag3PO4 membrane has the properties of self-buoyancy, electrical conductivity, and superior flexibility. Therefore, considering the simple preparation method and fine performances, the PCC-MXene/Ag3PO4 mixed membrane has great application potential in the study of interface evaporation, photodegradation of organic dyes, and antibacterial properties.

Efficient pure oxygen separation with the unique graded porous supported symmetric flat mixed conductor ceramic membrane

A graded porous supported symmetric (GPSS) flat ceramic membrane made of a K2NiF4+δ type oxide (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+δ (PLNCG) is fabricated by aqueous tape casting. This membrane design stands out for its unique structure, consisting of a thin dense layer at its core and two graded porous substrates that adhere symmetrically to this middle layer. In comparison to previously reported PLNCG hollow fiber membranes, the GPSS membrane offers superior oxygen permeation flux, exceeding that of the hollow fiber membrane by more than four times. When using air as the feed gas and even when introducing CO2 into the feed gas or sweep gas, the membrane maintains a consistent oxygen permeation flux of 4.41 mL min−1 cm−2 (STP). This work demonstrates that by paying close attention to membrane structure, the oxygen permeation flux of flat membranes can surpass that of hollow fiber membranes. Given its exceptional oxygen separation performance, the PLNCG-GPSS membrane holds great potential for practical applications such as high-purity oxygen production, pure hydrogen production, oxygen-involved catalytical reactions, and CO2 capture and storage.