Single Gas Permeation Research Articles

Revisiting the Effect of the Resistance to Gas Accumulation in Constant Volume Systems on the Membrane Time Lag.

The time-lag method is commonly used to determine membrane permeability, diffusivity and solubility in a single gas permeation experiment in a constant volume system. An unwritten assumption on which this method relies is that there is no resistance to gas accumulation in the downstream receiver of the system. However, this is not the case, even with the specially designed receiver used in this study when, in addition to tubing, the receiver utilizes an additional accumulation tank. The resistance to gas accumulation originates from a finite diffusivity (Knudsen diffusion) of gases in tubing, which are magnified by "resistance-free" accumulation tank(s). As a result of the resistance to gas accumulation, the time lag of the membrane is underestimated, which leads to an overestimation of gas diffusivity in the membrane. The experimentally predicted resistances in different configurations of the receiver, expressed by the difference in the time lag at two different receiver locations, were several times greater than the theoretically predicted values. A high molecular PPO membrane was used to demonstrate this effect. The time lags measured at different locations differed by as much as 30%. The diffusivity of nitrogen in a PPO of 4.04 × 10-12 m2/s determined at the optimum configuration of the receiver is at least 50% lower than the literature-reported values.

Determination of time lag by accurate monitoring of pressure decay in a new generation constant volume system

The time-lag method is the standard approach for evaluating membrane permeability, diffusivity and solubility in a single gas permeation experiment. The conventional time-lag method relies on accurately monitoring the pressure rise in a constant volume downstream from the membrane following a change in pressure upstream from the membrane. The same information could be extracted from the upstream pressure decay in the same time-lag experiment. However, accurately monitoring the pressure decay presents a challenge due to the resolution limitations of absolute pressure transducers. If the membrane was characterized based on pressure decay, a mass spectrometer could be used to simultaneously monitor the composition of the gas permeating from the membrane, opening the time-lag method to gas mixtures. Also, the simultaneous monitoring of pressure rise and decay could provide additional information about gas transport in the membrane, which is critical for more complex membrane materials.•The resolution challenge was overcome by splitting the upstream volume into the working and reference volumes and monitoring pressure decay using a differential pressure transducer between the two volumes.•The validity of the measured pressure decay was confirmed by the unique relation between the upstream and downstream time lags for a commercial PDMS membrane.

Enhanced hydrogen separation performance of cobalt-doped microporous silica membranes: Influence of cobalt content and processing parameters

This research focused on synthesizing microporous silica and cobalt-doped silica through acid-catalyzed hydrolysis and condensation. The effects of various synthesis parameters (calcination temperature, cobalt content, and cobalt addition step) were investigated. The results confirmed that the presence of cobalt in the microporous structure enhances the performance of the silica membrane. However, the hydrothermal stability remained unchanged, which can be attributed to the pore size of the silica. The competitive cobalt-doped silica sol coated on a modified support, resulting in a membrane with better performance compared to the blank silica membrane. The membrane was subjected to single gas permeation tests: H2 permeance of 1.8 × 10−7 mol m−2 s−1 Pa−1 and H2/N2 selectivity of 58 at a low temperature of 200 °C. The high apparent activation energy (Ea) observed for H2, suggests the presence of a molecular sieving mechanism, which was further improved by incorporating cobalt into the microporous structure of silica.

Single-file diffusion and its influence on membrane gas separation: A case study on UTSA-280

Gas permeation in metal-organic framework-based (MOF-based) membranes is often elucidated through the solution-diffusion model, where the adsorption and diffusion of gases play equally vital roles. This study draws attention to a unique phenomenon known as single-file diffusion (SFD) occurring within MOF membranes that possess ultramicropores with dimensions comparable to the gas molecules themselves. When SFD takes place, the separation performance becomes solely reliant on the adsorption quantities on the feed side of the membrane. As a proof of concept, we fabricated a UTSA-280 membrane and subjected it to testing using gas mixtures of CO2/N2 and CO2/CH4. Two crucial observations substantiate the occurrence of single-file diffusion. Firstly, in the gas mixtures, the diffusion coefficients of N2 or CH4 were observed to align closely with that of CO2, despite the intrinsic diffusion coefficients of CO2, N2, and CH4, as determined from single-gas permeation experiments, exhibiting differences. Secondly, the CO2 mole fractions within the adsorption phase closely mirrored those in the gas phase on the permeate side. Given the high adsorption selectivity of UTSA-280 for CO2, the UTSA-280 membrane delivers outstanding permeation selectivity for CO2/N2 (611) and CO2/CH4 (80.7). Our experimental findings are supported by mesoscale kinetic Monte Carlo simulations, which confirmed the relation between the CO2 compositions in the adsorption phase on the feed side and in the gas phase on the permeate side. Furthermore, density functional theory calculations revealed high energy barriers associated with CO2 surpassing its counterparts, rendering such processes unfavorable, thereby reinforcing our experimental findings regarding single-file diffusion.

Characterization and synthesis of high permeance SSZ-13 membranes to separate CO2 from CH4 for biogas upgrading

Small-pore zeolites, such as CHA (0.38 nm), have pores that are comparable to the size of CH4 but larger than the size of CO2. As a result of the combination of diffusion and adsorption, these membranes are projected to have strong CO2/CH4 selectivity and CO2 permeance. During this work, SSZ-13 CHA membranes were synthesized, evaluated, and characterized by X-ray Diffraction, Field-Emission Scanning Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, Fourier Transform Infrared Spectroscopy, Solid-State Nuclear Magnetic Resonance, and Thermogravimetric Analysis. Synthesized membranes on the inner surface of single channel alumina supports with a pore size of 200 nm and a length of 105 mm and an active membrane area of ∼17 cm2 showed an ideal permselectivity for CO2/CH4 of 122 (in the single gas permeation measurement) and a CO2 permeance of 36.1 × 10−7 [mol/(m2 s Pa)] and CO2/CH4 selectivity of 173 and a CO2 permeance of 6.5 × 10−7 [mol/(m2 s Pa)] for equimolar CO2 − CH4 mixture. According to the results, the membranes are capable of separating CO2 from natural gas and upgrading biogas for industrial purposes.

Fabrication of 3-(trihydroxysilyl)-1-propanesulfonic acid membranes with superior affinity and selectivity for NH3 permeation over H2 and N2 at 50–300 °C

Ammonia (NH3) produced by Haber-Bosch process is separated through the condensation process, which needs a large amount of energy consumption. Membrane separation technology is compelling for achieving energy-saving and efficient NH3 separation. Therefore, 3-(trihydroxysilyl)-1-propanesulfonic acid (TPS) was applied, for the first time, to fabricate sulfonic silica-based membranes and evaluated for NH3 selective permeation. The amorphous siloxane network can be formed by simple condensation of silanol (Si–OH) under sulfonic acid (-SO3H) self-catalysis, as confirmed by the results of Fourier transform infrared spectroscopy and X-Ray diffractometry. Moreover, TPS xerogel powders dried from TPS sols showed excellent thermal stability and dense structure via thermogravimetric and N2 adsorption analyses. Importantly, an intensive NH3 adsorption amount of ∼3.0 mmol g−1 for TPS xerogels from NH3 adsorption and temperature-programmed desorption was twice higher than the reported oxidized (3-mercaptopropyl)trimethoxysilane xerogels (∼1.41 mmol g−1), which was ascribed to the inherently stronger proton-acidic -SO3H groups in TPS. Finally, TPS membranes prepared using TPS solutions diluted with ethanol expressed superior NH3-selective permeation based on favorable molecular sieving and NH3 adsorption-diffusion via single and binary gas permeation, especially remarkable NH3 permeance of ∼2.6 × 10−7 mol m−2 s−1 Pa−1 and excellent NH3/N2 selectivity of 266 at 300 °C.

Microporous Adsorbent-Based Mixed Matrix Membranes for CO2/N2 Separation

As the atmospheric carbon dioxide (CO2) concentration rapidly rises, carbon capture, utilization, and storage (CCUS) is an emerging field for climate change mitigation. Various carbon capture technologies are in development with the help of adsorbents, membranes, solvent-based systems, etc. One of the main challenges in this field is the removal of CO2 from nitrogen (N2) gas. This paper focuses on mixed matrix membrane technology, for which the CO2/N2 separation performance is based on differences in gas permeations. Membrane separation and purification technologies are widely studied for carbon capture. Microporous adsorbents such as zeolites and metal organic frameworks (MOFs) for carbon capture have been attracting researchers’ attention due to their highly porous structures, high selectivity values, and tunable porosities. Utilizing microporous adsorbents dispersed within a novel, blended polymer matrix, fourteen membranes were prepared with the commercial MOF ZIF-8, zeolite 13X, and kaolin, with methyl cellulose (MC) and polyvinyl alcohol (PVA), which were tested using a single gas permeation setup in this study. The addition of polyallylamine (PAH) as a chemisorbent was also investigated. These membranes were synthesized both with and without a polyacrylonitrile (PAN) support to compare their performances. MC was found to be an ideal polymeric matrix component to develop free-standing MMMs. At 24 °C and a relatively low feed pressure of 2.36 atm, a free-standing zeolite-13X-based membrane (MC/PAH/13X/PVA) exhibited the highest N2/CO2 selectivity of 2.8, with a very high N2 permeability of 6.9 × 107 Barrer. Upon the optimization of active layer thickness and filler weight percentages, this easily fabricated free-standing MMM made of readily available materials is a promising candidate for CO2 purification through nitrogen removal.

Development and investigation of a multilayer PDMS/zeolite composite membrane for CO2 separation applications

This work aims to investigate and develop a concept for CO2 separation based on PDMS/SSZ–13 (high-Si CHA) composite membranes. Firstly, an Al2O3 support was coated with SSZ-13 zeolite layer, then to increase the performance of the membrane, a Polydimethylsiloxane layer was effectively deposited homogeneously to cover the cracks and defects of the zeolite layer. The results of single gas permeation measurements displayed a notable increase in ideal CO2/CH4 selectivity up to 428 at the lowest PDMS concentration of 0.5 vol%. Moreover, a coating time of 10 min preserved CO2 permeance while increasing CO2/CH4 selectivity from 5 to 120. A twentyfold increase in CO2/CH4 selectivity was noted with mixed gas permeation without a reduction in CO2 permeance. Quantitative and qualitative microscopic analyses were also carried out on the coated membrane to better understand its morphology and microstructure. The outcomes indicated that PDMS layer decreased the permeation of N2 and CH4 and enhanced surface affinity toward CO2, resulting in reduced defects in the zeolite membranes and enhanced selectivity for CO2/N2 and CO2/CH4.

Preparation and Gas Separation of Amorphous Silicon Oxycarbide Membrane Supported on Silicon Nitride Membrane.

An amorphous silicon oxycarbide membrane supported on a silicon nitride membrane substrate was prepared. A starting suspension containing polyhydromethylsiloxane (PHMS), tetramethyltetravinyl-cyclotetrasiloxane (TMTVS) and a platinum catalyst was first prepared and spin-coated on a silicon nitride membrane, and then the suspension was cross-linked and cured, followed by pyrolyzing at 1000 °C under a flowing Ar atmosphere. A dense amorphous silicon oxycarbon ceramic membrane with a thickness of about 1.8 µm was strongly bonded to the Si3N4 membrane substrate. The single gas permeation of H2 and CO2 indicated that the ideal permeation selectivity of H2/CO2 was up to 20 at 25 °C and 0.5 MPa with good long-term stability, indicating the potential application of the obtained membrane for hydrogen purification.

Single and mixed gas permeability studies on mixed matrix membranes composed of MIL-101(Cr) or MIL-177(Ti) and highly permeable polymers of intrinsic microporosity

The gas transport properties of mixed matrix membranes (MMMs), prepared by dispersing nanoparticles of MOFs MIL-101(Cr) or MIL-177(Ti) into highly permeable Polymers of Intrinsic Microporosity PIM-EA-TB or PIM-TMN-Trip, were investigated. The homogeneity of the dispersion was confirmed by means of Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray (EDX) mapping analysis. Single gas time-lag measurements provided the permeability and ideal selectivity of different gas pairs, both after treatment of the MMMs with methanol and after natural aging over an extended period (up to 2000 days). This data demonstrated that the gas size-sieving pores of MIL-101(Cr) and MIL-177(Ti) and their good dispersion into the PIM matrix results in MMMs with enhanced gas separation performance, as compared to films composed solely of the polymer. The comparison of actual permeability with the Maxwell model for PIM-EA-TB with both MOFs confirmed the good dispersion and the absence of anomalies, whereas the inconsistency of permeability with prediction data for PIM-TMN-Trip suggests that the MOFs improved the polymer properties, stiffening or occupying the polymer free volume. In particular, the incorporation of MIL-101(Cr) into PIM-EA-TB significantly enhances the H2 permeability from ∼6000 to 13,000 Barrer, with a concurrent increase of the H2/N2 selectivity from 14 to 21. MIL-177(Ti) also enhances the H2/N2 selectivity to 20 due to a slight reduction of the N2 permeability. The addition of MIL-101(Cr) and MIL-177(Ti) into the ultra-permeable PIM-TMN-Trip showed more modest increases in H2 permeability and H2/N2 selectivity from 4.6 to ∼ 10. Hence the data for some of the MMMs surpass the 2008, and even approach the 2015/2019 Robeson’s upper bounds, particularly for gas pairs including H2.

Pervaporation dehydration of an isopropanol aqueous solution using microporous TiO2-SiO2-OCL (Organic chelating Ligand) composite membranes prepared under different firing conditions

Microporous TiO2-SiO2 composite membranes intended for use in the pervaporation dehydration of a water/isopropanol mixture were prepared via the sol–gel method using acetylacetone (ACA) as an organic chelating ligand (OCL). TiO2-SiO2-ACA sols were prepared by using titanium (IV) propoxide (TiTP), an alkoxide of Ti, tetraorthoethylsilicate (TEOS), an alkoxide of Si, and ACA, as a composite of TiO2 and SiO2 with coordinating OCL to Ti. The dried gels were fired at 300 °C under N2 or at 500 °C under air, and were analyzed via FT-IR. Both powders had Ti-O-Si bonds, however, OCL in the powder fired at 500 °C in air has decomposed and removed. The TiO2-SiO2-ACA sols were applied to alumina plates and fired at either 300 °C under N2 or at 500 °C under air to check the water-contact angle, which indicated that the OCL was retained on the plates fired at 300 °C under N2 and were more hydrophobic than when fired at 500 °C under air. TiO2-SiO2-ACA composite membranes were fabricated by coating either the TiO2-SiO2-ACA sol layer fired at 300 °C under N2 or that fired at 500 °C under air onto a TiO2-SiO2 intermediate layer with an α-alumina support. The pore sizes of both membranes were estimated via the NKP method for single-gas permeance at 200 °C. The mean pore sizes of the membranes fired under N2 at 300 °C and under air at 500 °C were 0.47 nm and 0.68 nm, respectively, which suggested the possibility of pore size control via firing conditions. Pervaporation tests of the TiO2-SiO2-ACA composite membranes in a water/isopropanol mixture (IPA: 90 wt%) showed that the membranes fired under air at 500 °C and under N2 at 300 °C had values for permeation flux of 0.90 and 0.13 kg/(m2 h) and separation factors of 667 and 98 at 50 °C, respectively. The higher permeation flux of the membrane fired under air at 500 °C was due to the influence of a larger pore size as well as to a more hydrophilic surface. On the other hand, the separation factor was also higher for the membrane fired under air at 500 °C, because the hydrophilic surface facilitated water permeation. These results indicate the possibility of using firing conditions to control both the pore size and the surface properties of microporous TiO2-SiO2-ACA composite membranes for use in PV separation.

Composite membranes based on ether oxygen-rich polyimide with superior CO2/N2 separation properties prepared by interfacial polymerization

Ether oxygen-rich polymeric membranes emerge as promising membranes in CO2 separation due to the high affinity between CO2 molecules and ethylene oxide segments. However, there is a massive challenge in developing asymmetric membranes with high CO2 permeation performance and CO2/light gas separation performance. This work revealed composite membranes with ether oxygen-rich polyimide separation layers were developed by interfacial polymerization between 1,2,4,5-benzenetetracarbonyl tetrachloride and commercial diamines named o,o'-bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol followed by thermal imidization. The influences of the polymerization time and monomer concentrations on the gas transport and separation properties of the composite membranes were studied based on single-gas permeation. The optimum membrane possessed a superior high ideal CO2/N2 separation factor of 429 accompanied with a moderate permeance of 150 GPU for CO2 at 25oC and 0.2 MPa. The performance stability was studied by operating the membrane at various pressures and temperatures. The result showed the composite membrane possessed excellent plasticization resistivity at high pressures. The separation property of composite membranes for CO2/N2 binary mixture was also evaluated. The influences of the operation parameters, including stage-cut and pressure ratio on the product purity and recovery were investigated. The results showed great practical application potential in efficient separation of flue gas.

Innovative NH3 separation over immobilized molten salt membrane at high temperatures

In industry, CO2 emissions can be mitigated by replacing conventional ammonia separation techniques withenergy-efficient systems. In this study, a ZnCl2 immobilized molten salt (IMS) membrane was synthesized and evaluated for the potential separation of NH3 from a gas mixture containing N2 and H2. The membrane was prepared via the direct deposition technique, and several permeation tests were performed to evaluate its permeation characteristics at atmospheric pressure with temperatures ranging from 290 °C to 325 °C. For single gas permeation at 300 °C, NH3 permeance was found to be as high as 182 GPU, with NH3/N2 and NH3/H2 ideal selectivities of 11,375 and > 107, respectively. For binary mixtures (10 %/90 % NH3/N2 and NH3/H2), NH3 permeance as high as 825 GPU was achieved at the same operating conditions. Remarkably, higher permeance (∼1100 GPU) was obtained by feeding ternary mixtures (11 %/67 %/23 % NH3/H2/N2) at a temperature of 325 °C. An exceptionally high NH3 purity (99.9 %) was achieved in the permeate stream. The IMS membrane exhibits prolonged stability, working for more than 180 h with no significant performance loss. This pioneering study shows that the ZnCl2 IMS membrane can be used to separate NH3 at high temperatures with a potential application for treating downstream ammonia in the industrial Haber Bosch process.

Gas permeation properties of bridged-type organosilica membranes at extremely low temperatures and the application to oxygen separation

A bridged-type organosilica, bis(triethoxysilyl)methane (BTESM) membrane was evaluated in detail for single-gas permeation at temperatures ranging from −130 to −200 °C, and for binary (O2/He, O2/N2) separation at 30 and -115 °C, respectively. The permeance of He, Ar, and N2 demonstrated a trend of activated diffusion as permeance increased with an increase in the temperature; O2 permeance, however, reached its maximum value at about −80 °C. O2 permeance increased with a decrease in the temperature (30 to −80 °C), and permeance then gradually decreased (−80 to −130 °C), which demonstrates surface diffusion. In the case of O2/He binary separation, both O2 and He permeated according to molecular sieving at 30 °C, but at −115 °C, O2/He selectivity was enhanced approximately 10-fold due to permeation blockage by adsorbed O2. On the other hand, in the case of O2/N2 binary separation at −115 °C, the effect of permeation blocking by adsorbed O2 permeance was lessened due to the effect of competitive adsorption, which translated to a level of O2/N2 selectivity that was only 1.5-fold higher than that at 30 °C.

Mixed Matrix Membranes Using Porous Organic Polymers (POPs)-Influence of Textural Properties on CO2/CH4 Separation.

Mixed matrix membranes (MMMs) provide the opportunity to test new porous materials in challenging applications. A series of low-cost porous organic polymer (POPs) networks, possessing tunable porosity and high CO2 uptake, has been obtained by aromatic electrophilic substitution reactions of biphenyl, 9,10-dihydro-9,10-dimethyl-9,10-ethanoanthracene (DMDHA), triptycene and 1,3,5-triphenylbenzene (135TPB) with dimethoxymethane (DMM). These materials have been characterized by FTIR, 13C NMR, WAXD, TGA, SEM, and CO2 uptake. Finally, different loadings of these POPs have been introduced into Matrimid, Pebax, and chitosan:polyvinyl alcohol blends as polymeric matrices to prepare MMMs. The CO2/CH4 separation performance of these MMMs has been evaluated by single and mixed gas permeation experiments at 4 bar and room temperature. The effect of the porosity of the porous fillers on the membrane separation behavior and the compatibility between them and the different polymer matrices on membrane design and fabrication has been studied by Maxwell model equations as a function of the gas permeability of the pure polymers, porosity, and loading of the fillers in the MMMs. Although the gas transport properties showed an increasing deviation from ideal Maxwell equation prediction with increasing porosity of the POP fillers and increasing hydrophilicity of the polymer matrices, the behavior of biopolymer-based CS:PVA MMMs approached that of Pebax-based MMMs, giving scope to not only new filler materials but also sustainable polymer choices to find a place in membrane technology.

Investigation of the effect of Ni and Cu variant MOF-74 in the Polydimethylsiloxane (PDMS)-based Mixed Matrix Membranes (MMMs) for efficient gas separation applications.

Mixed matrix membranes (MMMs) containing metal-organic frameworks (MOFs) have been an emerging and promising membrane technology to contribute to different gas separation applications including carbon dioxide (CO2) and oxygen (O2) separation, because of their large surface areas and distinctive gas adsorption features. In this work, the fabrication process of Polydimethylsiloxane (PDMS)-based MMMs was reported, in which 0.5 to 2 wt.% of each type of (Cu, Ni)-based MOF-74 variants were incorporated into a PDMS matrix in order to achieve high CO2/N2, O2/N2, and CO2/O2 separation efficiency. These MMMs and their nanofillers (MOF-74) were extensively characterized using scanning electron microscopy (SEM) along with Energy Dispersive X-Ray (EDX) mapping, X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), a single gas permeation testing system, and an ultimate tensile strength testing (UTS) unit in order to gain insight into their properties in relation to their gas separation performance. The 1 wt.% of both (Cu and Ni)-MOF-74@PDMS were selected as the most optimum MMMs due to their uniform morphology and enhanced tensile strength, which exhibited high CO2 permeabilities of 4432 Barrer (37.9% increase) and 4288 Barrer (33.5% increase), respectively. Furthermore, in the case of 1 wt.% Ni-MOF-74@PDMS, the CO2/N2, O2/N2, and CO2/O2 selectivities were also enhanced to 36.2 (141.6% increase), 3.2 (21.9% increase), and 11.25 (98.1% increase), respectively. While, in the case of 1 wt.% Cu-MOF-74@PDMS the CO2/N2 and O2/N2 selectivities showed an increment up-to 94.7 (531.5% increase) and 6.47 (145% increase), respectively, Whereas, at 0.5 wt.%, Cu-MOF-74@PDMS showed the best CO2/O2 selectivity of 25.26 (344.7% increase).

Taguchi Design Methodology for the Optimization of CO2 Permeance in Gas Capture Process from Polluted Air

CO2 single-gas permeance has been studied in the present work by the ssz-13 membrane. SEM was used to characterize the membranes. Feed flow rate, Feed pressure, Sweep gas flow rate as the studied parameters, and these factors varied at five levels with an orthogonal array of L25. Applying Taguchi experimental design allowed to examine the impact of the most important parameters on membrane permeabilit. CO2 permeance had the biggest effect by feed flow rate.

Polarization enhanced CH4/N2 separation in bromine functionalized ZIF-62 based mixed-matrix membranes

Owing to the similarities in polarity, kinetic size, and boiling point, CH4 and N2 separation remains difficult and energy-consuming. However, the difference in polarizability offers an opportunity for boosting the separation by differentiating their interactions with the metal-organic framework (MOF). Herein, bromine (Br) functional group is rationally introduced into ZIF-62 to strengthen CH4/N2 separation through the polarization effect. The anisotropic charge distribution on Br atom can induce electron cloud deformation of gas molecules, especially CH4 molecules with higher polarizability, thus generating differentiated interactions. As a result, ZIF-62-Br exhibits a 69.7% increase in CH4 adsorption capacity and obviously improved selectivity compared with the ZIF-62, and embedding ZIF-62-Br in the polyethyleneimine (PEI) matrix endows the obtained mixed-matrix membranes (MMMs) with good CH4/N2 separation performance (CH4 permeance of 3157 GPU and CH4/N2 ideal selectivity of 7.6 for single gas permeations, and CH4 permeance of 2235 GPU and CH4/N2 selectivity of 4.2 for mixed gas tests). The good separation performance and stability suggest that MMMs fabricated with ZIF-62-Br in this work can be a promising candidate for facilitating the exploration of CH4/N2 membrane separation.

Novel polymer composite coated with ethylcellulose nanoparticle from waste paper as an alternative material to extracorporeal oxygenation membrane

Extracorporeal membrane oxygenator (ECMO) is a valuable technology to support people with acute respiratory distress syndrome (ARDS) and is recommended for COVID-19 patients. This study aims to fabricate polymer-based composite membranes coated with ethylcellulose nanoparticles from waste paper and identify the performance of the composite as ECMO candidates. Composite membranes were made from four types of polymers, namely, nylon, PTFE (polytetrafluoroethylene), Pebax® MH-1657, and SBS (poly-(styrene-b-butadiene-b-styrene)). PDMS (polydimethylsiloxane) 1 wt.% and ethylcellulose nanoparticles (3% and 10 wt.%) were used as membrane coatings to increase their hydrophobic properties. The success of cellulose isolation and ethylcellulose synthesis from waste paper was confirmed by the FTIR and XRD analysis. The size of the synthesized ethylcellulose nanoparticles was 32.68 nm. The coating effect on composite membranes was studied by measuring the contact angle, membrane porosity, protein quantification tests, and single gas permeation of O2 and CO2. Based on the protein quantification test, the protein could not pass through the Pebax/PDMS and SBS/PDMS composites coated with 10 wt.% ethylcellulose; this indicated less risk of plasma leakage. The gas permeation test on nylon/PDMS, PTFE/PDMS, and SBS/PDMS composites coated with 10% ethylcellulose resulted high CO2/O2 selectivity, respectively, 2.17, 3.48, and 3.22 as good indication for extracorporeal oxygenation membrane.

Preparation, Characterization and Hydrothermal Stability of Hydrophobic TiO2/SiO2 Membrane

Hydrophobic TiO2/SiO2 (TiO2/HSiO2) membrane was fabricated by sol-gel method using methyltriethoxysilane as a precursor instead of partial tetraethylorthosilicate. The thermal stability of the composites was characterized by Fourier transform infrared spectra, X-ray diffraction, thermogravimetric-differential thermogravimetric analysis and N2 adsorption-desorption measurements. The H2 permeation and H2 permselectivity of TiO2/HSiO2 membrane were investigated by single gas permeance test. Calcination at about 350 ∼ 400 °C is suitable for preserving the hydrophobicity of the TiO2/HSiO2 membrane. The H2 permeance and H2 permselectivity in TiO2/HSiO2 membranes increased significantly with growing temperatures. At 200 °C and 0.4 MPa, the H2 permeance of TiO2/HSiO2 membrane is 7.27 × 10−6 mol·m−2·Pa−1·s−1 and the H2/CO2 and H2/N2 permselectivities are 7.68 and 10.09, respectively. In comparison to the HSiO2 membrane, the H2 permeances of TiO2/HSiO2 membrane increased by 71.56%, and the H2/CO2 and H2/N2 permselectivities increased by 23.07% and 24.11%, respectively. After steam treatment, the water absorption rate of TiO2/HSiO2 materials decreased by 33.17% relative to that of HSiO2 materials. TiO2/HSiO2 membrane has better hydrothermal stability and reproducibility than HSiO2 membrane.