Thin Selective Layer Research Articles

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.

CO<sub>2</sub> Absorption/Desorption on Gas-Liquid Membrane Contactors Using Monoethanolamine Solvent: Comparison of Porous and Composite Hollow Fibers

The operating efficiency of asymmetric porous and composite membranes with a thin non-porous selective layer was compared in the processes of CO2 absorption and desorption in gas-liquid membrane contactors using aqueous solutions of monoethanolamine (MEA) with low concentration (<14 %). Composite membranes were prepared by direct deposition of poly (1-trimethylsilyl-1-propyne) (PTMSP) in a hollow fiber membrane module. The effects of gas flow rate and MEA solvent linear velocity on the CO2 mass transfer were evaluated. Porous membranes were shown to be more effective in the process of CO2 absorption, because they allow to remove more than 90 % of CO2 from the gas mixture during one pass of the solvent through the contactor. Composite membranes were more promising for CO2 desorption, since they provide half as much of the solvent vapor losses with comparable desorbed CO2 fluxes (0.12-(STP)/(m2·h)). The contributions of membrane and liquid phase to the overall mass transfer resistance during the CO2 absorption process were estimated. It was demonstrated that deposition of a thin selective layer from a highly permeable PTMSP with a thickness of only 3 μm increases the membrane contribution to the total mass transfer resistance from 10-20 % to 60-80 %.

New Method toward a Robust Covalently Attached Cross-Linked Nanofiltration Membrane.

As nanofiltration applications increase in diversity, there is a need for new fabrication methods to prepare chemically and thermally stable membranes with high retention performance. In this work, thio-bromo “click” chemistry was adapted for the fabrication of a robust covalently attached and ultrathin nanofiltration membrane. The selective layer was formed on a pre-functionalized porous ceramic surface via a novel, liquid–vapor interfacial polymerization method. Compared to the most common conventional interfacial polymerization procedure, no harmful solvents and a minimal amount of reagents were used. The properties of the membrane selective layer and its free-standing equivalent were characterized by complementary physicochemical analysis. The stability of the thin selective layer was established in water, ethanol, non-polar solvents, and up to 150 °C. The potential as a nanofiltration membrane was confirmed through solvent permeability tests (water, ethanol, hexane, and toluene), PEG-in-water molecular weight cut-off measurements (≈700 g mol–1), and dye retention measurements.

Electrospun nanofiber supports with bio-inspired modification enabled high-performance forward osmosis composite membranes

Electrospun nanofiber mats (ENMs) are desired candidates as supports for composite forward osmosis (FO) membranes owning to the high porosity and low tortuosity of pores. However, it remains challenge to construct defect-free thin selective layer on ENMs controllably to achieve simultaneous high permeability and selectivity. In order to meet the demands, a novel thin film composite (TFC) FO membrane was fabricated via interfacial polymerization on a polydopamine (PDA) modified ENM substrate (PDA-HPENM), which was hot-pressed (HPENMs) prior to the PDA deposition to improve the mechanical strength and reduce the mat thickness. The internal concentration polarization (ICP) effects and the transmembrane resistance in FO membranes are reduced significantly attributed to the unique pore structure and good hydrophilicity of the PDA-HPENMs, resulting in doubled water flux compared with that of the TFC membranes using HPENM substrates. Moreover, the optimized TFC FO membranes exhibit relatively high rejection (~100%) to heavy metal ions and antibiotics, holding great potential for wastewater treatment.

Suppressed crystallization and enhanced gas permeability in thin films of cellulose acetate blends

Film thickness and blending can affect crystallization and chain dynamics of semi-crystalline polymers, particularly for submicron films. Herein we apply these insights to elucidate a long-standing puzzle for industrial asymmetric membranes for CO2 removal from natural gas, which are based on blends of cellulose diacetate (CDA with a degree of acetylation or DS of 2.45) and cellulose triacetate (CTA with a DS of 2.87). The asymmetric membranes comprise thin selective layers (~100 nm) and have been reported to exhibit gas permeability much higher than the bulk blends. We hypothesize that the film thickness and blending confine crystallization and decrease the crystallinity, increasing gas permeability while retaining high selectivity. Specifically, we systematically determined crystallinity for CTA and two blends with various thicknesses ranging from ≈500 nm to ≈20 μm. Adding 75 mass% CTA in CDA (CDA-CTA75) decreases the crystallinity from 34 vol% to 23 vol% at ≈ 20 μm (accompanied by CO2 permeability increase from 3.9 Barrer to 7.1 Barrer), while decreasing the film thickness of CDA-CTA75 from ≈20 μm to ≈ 1.0 μm decreases the crystallinity from 23 vol% to 13 vol% and increases CO2 permeability from 7.1 Barrer to 14 Barrer. Understanding polymer chain dynamics and crystallization in thin films can be instrumental in designing high-performance membranes for industrial gas separations.

Toward Sustainable Tackling of Biofouling Implications and Improved Performance of TFC FO Membranes Modified by Ag-MOF Nanorods.

In this work, nanorods with high antibacterial properties were synthesized with silver acetate as the metal source and 2-aminoterephthalic acid as the organic linker and were then embedded into thin-film composite (TFC) membranes to amend their performance as well as to alleviate biofouling. Silver metal-organic framework (Ag-MOF) nanorods with a length smaller than 40 nm were incorporated within the polyamide thin selective layer of the membranes during interfacial polymerization. The interaction of the synthesized nanorods with the polyamide was favored because of the presence of amine-containing functional groups on the nanorod's surface. The results of X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and atomic force microscopy characterizations proved the presence of Ag-MOF nanorods in the selective layer of thin-film nanocomposite (TFN) membranes. TFN membranes demonstrated improved water permeance, salt selectivity, and superior antibacterial properties. Specifically, the increased hydrophilicity and antibacterial potential of the TFN membranes led to a synergetic effect toward biofouling mitigation. The number of live bacteria attached to the surface of the neat TFC membrane decreased by more than 92% when a low amount of Ag-MOF nanorods (0.2 wt %) was applied. Following contact of the TFN membrane surface with Escherichia coli and Staphylococcus aureus, full inactivation, and degradation of bacteria cells were observed with microscopy, colony-forming unit tests, and disc inhibition zone analyses. This result translated to a negligible amount of the biofilm formed on the active layer. Indeed, the incorporation of Ag-MOF nanorods decreased the metal-ion release rate and therefore provided prolonged antibacterial performance.

Membranes with Well‐Defined Selective Layer Regulated by Controlled Solvent Diffusion for High Power Density Flow Battery

AbstractMembranes with precise control of selective layer are designed and prepared by adjusting diffusion of solvents. Combining experiments and theoretical calculations, the formation mechanism of ion conductive membranes prepared by a non‐solvent induced phase separation (NIPS) method is found to be related to internal diffusion flux of solvent to the non‐solvent bath and external diffusion flux of non‐solvent to the casting solution. By regulating the internal and external diffusion rates via a two‐step NIPS method, a series of polybenzimidazole (PBI) porous membranes with independently controlled thin selective skin layers and highly porous support layers are fabricated, which achieve a simultaneous improvement in ion selectivity and proton conductivity. A vanadium flow battery assembled with a PBI membrane demonstrates an energy efficiency of 80% at a current density of 220 mA cm−2, which is the highest value among the reported PBI membranes. This provides a simple and effective way to fabricate membranes with well‐defined morphologies.

Effect of the Formation of Ultrathin Selective Layers on the Structure and Performance of Thin-Film Composite Chitosan/PAN Membranes for Pervaporation Dehydration.

The aim of the study is to improve the performance of thin-film composite (TFC) membranes with a thin selective layer based on chitosan (CS) via different approaches by: (1) varying the concentration of the CS solution; (2) changing the porosity of substrates from polyacrylonitrile (PAN); (3) deposition of the additional ultrathin layers on the surface of the selective CS layer using interfacial polymerization and layer-by-layer assembly. The developed membranes were characterized by different methods of analyses (SEM and AFM, IR spectroscopy, measuring of water contact angles and porosity). The transport characteristics of the developed TFC membranes were studied in pervaporation separation of isopropanol/water mixtures. It was found that the application of the most porous PAN-4 substrate with combination of formation of an additional polyamide selective layer by interfacial polymerization on the surface of a dense selective CS layer with the subsequent layer-by-layer deposition of five bilayers of poly (sodium 4-styrenesulfonate)/CS polyelectrolyte pair led to the significant improvement of permeance and high selectivity for the entire concentration feed range. Thus, for TFC membrane on the PAN-4 substrate the optimal transport characteristics in pervaporation dehydration of isopropanol (12–90 wt.% water) were achieved: 0.22–1.30 kg/(m2h), 99.9 wt.% water in the permeate.

Cross-Linked Polyphosphazene Blends as Robust CO2 Separation Membranes.

An effective cross-linking technique allows a viscous and highly gas-permeable hydrophilic polyphosphazene to be cast as solid membrane films. By judicious blending with other polyphosphazenes to improve the mechanical properties, a membrane exhibiting the highest CO2 permeability (610 barrer) among polyphosphazenes combined with a good CO2/N2 selectivity (35) was synthesized and described here. The material demonstrates performance stability after 500 h of exposure to a coal-fired power plant flue gas, making it attractive for use in carbon capture applications. Its CO2/N2 selectivity under conditions up to full humidity is also stable, and although the gas permeability does decline, the performance is fully recovered upon drying. The high molecular weight of these heteropolymers also allows them to be cast as a thin selective layer on an asymmetric porous membrane, yielding a CO2 permeance of 1200 GPU and a CO2/N2 pure gas selectivity of 31, which does not decline over 2000 h. In addition to gas separation membranes, this cross-linked polyphosphazene can potentially be extended to other applications, such as drug delivery or proton exchange membranes, which take advantage of the polyphosphazene's versatile chemistry.

Recent Development in Composite Membranes for Flow Batteries.

Flow batteries (FBs) are one of the most attractive candidates for stationary energy storage and vital in realizing the wide application of renewable energies. Membranes play an important role in isolating redox couples while transporting ions to close the internal electrical circuit. Therefore, membranes with high selectivity and conductivity are highly important. Among different membranes, a composite membrane with independent design of support layer and thin selective top layer becomes one of the most promising candidates to break the trade-off between selectivity and conductivity. In this Review, recent studies on composite membranes for FBs and the principles of membrane design in different systems are discussed and summarized. Finally, the future direction on membrane design for different FBs is presented, which will provide an extensive, comprehensive reference to design and construct high-performance composite membranes for FBs.

Asymmetric mixed-matrix membranes incorporated with nitrogen-doped graphene nanosheets for highly selective gas separation

Conventional mixed-matrix membranes (MMMs) possess a dense structure with a filler material uniformly dispersed within the polymer matrix to engineer the transport properties and achieve enhanced gas separation performances with respect to pure polymeric membranes. However, a dense membrane structure increases the transport resistance and undesirably requires a high filler loading to see a substantial enhancement in separation performances. To address this problem, we fabricated asymmetric MMMs that have a thin-selective layer of around 0.5 μm and a low loading (0.03–0.10 wt%) of nitrogen-doped graphene (N-G) nanosheets. The presence of the nitrogen- and oxygen-containing functional groups on the N-G nanosheets ensured good compatibility between filler and polymer matrix, which resulted in strong polymer/filler interfacial adhesions. The N-G nanosheets were also found to be capable of migrating to the top of the membranes during phase inversion. Hence, despite the low filler loadings used in this work, the capacity of the dense selective layers was greatly enhanced. Based on our experimental results, 0.07 wt% and 0.10 wt% loading of N-G nanosheets can improve both O2/N2 (126.9%) and CO2/N2 (45.8%) selectivities with respect to pure polymeric membranes, resulting in O2/N2 separation performance surpassing the Robeson upper bound.

Development of thin film nanocomposite membrane incorporated with mesoporous synthetic hectorite and MSH@UiO-66-NH2 nanoparticles for efficient targeted feeds separation, and antibacterial performance

Functionalized metal-organic frameworks (MOFs) and their composites are found one of the best material to develop the thin-film nanocomposite (TFN) membranes and concern water purification technologies with boosted water flux and targeted feeds rejection performance. MOFs with suitable functionalities are found more stable and efficient due to strong interfacial polymerization with free functional groups which consequently resulted in a thin selective nanocomposite layer on the surface of polysulfone flat sheet membranes. Similarly, mesoporous synthetic hectorite (MSH), due to negative surface charge acts as the best support material to avoid high agglomeration of positively charged MOF crystals. Additionally, surface hydroxyl functionalities with high dispersion capability in a polymer monomer solution makes MSH as a promising material for MOF support and development of novel membranes. Herein considering all these advantageous aspects of both material, we have established a novel approach for developing of TFN membranes by incorporating MSH, and composite of MSH and MOF (UiO-66-NH2) nanoparticles in piperazine (PIP) aqueous monomer solution, which were further interfacially polymerized with trimesoyl chloride (TMC) organic phase monomer. The developed nanoparticles (MSH and MSH@UiO-66-NH2) formulation were confirmed by ideal characterization techniques such as, PXRD, FTIR, TGA and SEM. Whereas, alteration impact of MSH and MSH@UiO-66-NH2 nanoparticles on prepared membranes were physicochemically evaluated with original TFC membrane by ATR-FTIR, FE-SEM, HR-TEM, AFM, XPS, TGA, zeta potential and contact angle analysing techniques. The efficacy performance of the developed TFN membranes were compared with thin-film composite (TFC) membrane and found that TFN membranes showed excellent water flux and rejection performances against different synthetic feed solutions including most common salts (i. e. NaCl, Na2SO4, CuSO4, MgSO4, MnSO4), toxic boron in the seawater and bulky humic substances. Interestingly upon incorporation of a small amount of (0.01%) MSH and MSH@UiO-66-NH2 nanoparticles into the developed membrane dramatically improved rejection performance against applied feed solutions in the trend of TFC < MSH-TFN < MSH@UiO-66-NH2-TFN. The highest rejection 94.42% for MgSO4 was obtained along with the flux 34.78 L/m2.h at 1.5 MPa. Likewise, 69.56 L/m2.h flux with 71.23% rejection for boron at pH 8 (close to sea water) at 1.5 MPa. Due to hydrophilic and notable antifouling nature of TFN membranes the tested membrane shows excellent humic acid permeate flux of 80.68 L/m2.h and rejection of 98.96%. Besides, MSH@UiO-66-NH2-TFN membrane showed noteworthy antibacterial properties with efficient reduction in the bacterial colony growth. We believed that the present novel membrane modification approach has high potential in the development of high efficient water purification technologies in future.

Effect of the solvent nature on the structure and performance of poly(amide-imide) ultrafiltration membranes

The study covers the fundamental relationships between the nature of aprotic polar solvents [N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO)] used for casting solution preparation and the structure and performance of poly(amide-imide) (PAI) ultrafiltration membranes. It was found that the distinctive feature of the ternary systems PAI-poly(ethylene glycol) (PEG-400, Mn = 400 g mol−1) solvent is gel formation upon the increase in PEG-400 concentration in the solution. The PEG-400 addition to the casting solution was shown to increase pure water flux of the PAI membranes prepared from the casting solutions in different solvents. However, different patterns of the change of pure water flux when gel point is exceeded in PAI-PEG-400-solvent system were revealed. The PAI membranes obtained from the ternary systems PAI-PEG-400-solvent were found to combine high pure water flux at P = 0.1 MPa (130 L m−2 h−1 for DMSO, 120 L m−2 h−1 for DMA and 70 L m−2 h−1 for NMP) and high poly(vinylpyrrolidone) (PVP) rejection coefficients: 98–99% for PVP with Mn = 40000 g mol−1 and 86–95% for PVP with Mn = 10000 g mol−1. SEM studies reveal the significant difference in the PAI membrane structure when different solvents are used for casting solution preparation. The structure of the membranes obtained from 20 wt% PAI solutions in NMP and DMA consists of the thin selective layer supported by substructure pierced by elongated macrovoids. Meanwhile, when DMSO and DMF are used as solvents the addition of PEG-400 yields the suppression of macrovoid formation and anisotropic sponge-like membrane structure is obtained.

Composite Membranes Based on the Poly(1-trimethylsylyl-1-propine): Influence of the Porous Aromatic Frameworks Produced from the Friedel–Crafts Reaction and Introduced into the Polymer Matrix

The effect of particles of porous aromatic frameworks, synthesized by the Friedel–Crafts reaction (PAF-FC), introduced into matrix of glassy polymer poly(1-trimethylsilyl-1-propine) (PTMSP), on the stabilization of the transport characteristics of composite membranes with a thin selective layer (2.0–2.2 Μm) was studied. As a comparison, samples of composite membranes with a selective layer based on PTMSP and PTMSP filled with PAF-11 particles synthesized by the Suzuki reaction are considered. All samples of composite membranes showed a decrease in the absolute values of gas permeability for all gases over time due to relaxation of the nonequilibrium free volume of PTMSP, therewith the greatest decrease is observed during the first thousand hours since membrane creation. The stabilization of the transport characteristics of composite membranes with PTMSP/PAF-FC occurs after 5000 h since membrane creation, further the carbon dioxide performance remains at the level of 8–9 m3 m–2 h–1 atm–1 for 9200 h. Similar performance values for aged composite membranes based on PTMSP and PTMSP/PAF-11 were about 1.5 m3 m–2h–1 atm–1.

Methanol and Humidity Capacitive Sensors Based on Thin Films of MOF Nanoparticles.

The successful development of modern gas sensing technologies requires high sensitivity and selectivity coupled to cost effectiveness, which implies the necessity to miniaturize devices while reducing the amount of sensing material. The appealing alternative of integrating nanoparticles of a porous metal-organic framework (MOF) onto capacitive sensors based on interdigitated electrode (IDE) chips is presented. We report the deposition of MIL-96(Al) MOF thin films via the Langmuir-Blodgett (LB) method on the IDE chips, which allowed the study of their gas/vapor sensing properties. First, sorption studies of several organic vapors like methanol, toluene, chloroform, etc. were conducted on bulk MOF. The sorption data revealed that MIL-96(Al) presents high affinity toward water and methanol. Later on, ordered LB monolayer films of MIL-96(Al) particles of ∼200 nm were successfully deposited onto IDE chips with homogeneous coverage of the surface in comparison to conventional thin film fabrication techniques such as drop-casting. The sensing tests showed that MOF LB films were selective for water and methanol, and short response/recovery times were achieved. Finally, chemical vapor deposition (CVD) of a porous thin film of Parylene C (thickness ∼250-300 nm) was performed on top of the MOF LB films to fabricate a thin selective layer. The sensing results showed an increase in the water selectivity and sensitivity, while those of methanol showed a huge decrease. These results prove the feasibility of the LB technique for the fabrication of ordered MOF thin films onto IDE chips using very small MOF quantities.

High flux thin-film nanocomposites with embedded boron nitride nanotubes for nanofiltration

A novel thin film nanocomposite (TFN) membrane was obtained by incorporating boron nitride nanotubes (BNNTs) into a polyamide (PA) thin selective layer prepared via interfacial polymerisation. The addition of just 0.02 wt% of BNNTs led to a 4-fold increase in pure water permeance with no loss in rejection for divalent salts, methylene blue or humic acid compared to the pure PA membrane. Loadings higher than 0.02 wt% of BNNTs led to agglomeration with overall loss of performance. For the membranes containing 0.02 wt% BNNTs, the pure water permeance was 4.5 LMH@bar, with >90% rejection of MgSO4 and >80% rejection of CaCl2. Fouling tests with humic acid showed a flux recovery ratio of >95% with ~50% lower flux loss during the fouling cycle compared to the polyamide only membrane. These values represent a significant improvement over both commercial polyamide membranes and TFN membranes incorporating carbon nanotubes. We assert that the very small quantity of BNNTs needed to produce the enhanced performance opens the way to their use in water treatment applications where nanofiltration membranes are subject to severe organic fouling.

Membrane Absorption of Ethylene from a Mixture with Ethane Using MDK-3 Composite Membranes

Separation of olefin/paraffin mixtures is an important problem. The use of a gas—liquid membrane contactor is an attractive alternative to traditional power-consuming cryogenic distillation methods. The paper deals with the separation of ethylene from its mixture with ethane (component ratio 19/81 vol %, respectively) using an aqueous silver nitrate solution as a selective ethylene absorbent in a flat-sheet lab-scale membrane module equipped with an MDK-3 commercial composite membrane with the selective layer based on silicone rubber. The effect of the absorbent and gas mixture feed linear velocities on the residual ethylene content of the mixture is considered. The thin selective layer of the membrane is shown to preserve high performance during long-term experimental run ensuring high mass-exchange characteristics and preventing the absorbent penetration into the porous structure of the membrane support.

Novel thin-film composite pervaporation membrane with controllable crosslinking degree for enhanced water/alcohol separation performance

Thin-film composite (TFC) pervaporation membranes is of widespread interest for the alcohol dehydration, since the thin selective layer allows a high permeation flux. However, how to obtain the desired flux and separation selectivity simultaneously is still the bottleneck of industrial application with pervaporation technology. In this study, a novel ultrathin multi-layer polyurea or polyamide pervaporation membrane was designed and assembled via layer-by-layer (LBL) interfacial polymerization (IP) method on the hydrolyzed polyacrylonitrile (HPAN) substrate membrane. During the LBL assembly process, the controllable crosslinking degree of the separation layer formed through changing the concentration of the oil phase monomer while remaining the concentration of the aqueous phase monomer constant based on the solution-diffusion mechanism of pervaporation separation process. The surface characterization revealed that the tris(2-aminoethyl) amine (TAEA)1.5-toluene 2,4-diisocyanate (TDI)1-0.5-0/HPAN composite membrane exhibited much rougher surface than that of the membranes with the same crosslinking degree. The optimized composite membrane exhibited a high separation factor of 844.6 with a desirable permeation flux of 1284.3 g·m−2·h−1 for the pervaporation dehydration 95 wt% ethanol aqueous solution at 80 °C, which was 10-fold increase of separation factor compared with the control membrane. Moreover, the excellent operation stability of the TFC membrane demonstrated the promising prospect for the alcohol dehydration separation. This preparation methodology has potential application in other membrane separation process on the basis of solution-diffusion mechanism, such as gas separation and reverse osmosis membrane.

Highly Selective Oxygen/Nitrogen Separation Membrane Engineered Using a Porphyrin-Based Oxygen Carrier.

Air separation is very important from the viewpoint of the economic and environmental advantages. In this work, defect-free facilitated transport membranes based on poly(amide-12-b-ethylene oxide) (Pebax-2533) and tetra(p-methoxylphenyl)porphyrin cobalt chloride (T(p-OCH3)PPCoCl) were fabricated in systematically varied compositions for O2/N2 separation. T(p-OCH3)PPCoCl was introduced as carriers that selectively and reversibly interacted with O2 and facilitated O2 transport in the membrane. The T(p-OCH3)PPCoCl had good compatibility with the Pebax-2533 via the hydrogen bond interaction and formed a uniform and thin selective layer on the substrate. The O2 separation performance of the thin film composite (TFC) membranes was improved by adding a small amount of the T(p-OCH3)PPCoCl and decreasing the feed pressure. At the pressure of 0.035 MPa, the O2 permeability and O2/N2 selectivity of the 0.6 wt % T(p-OCH3)PPCoCl/Pebax-2533 was more than 3.5 times that of the Pebax-2533 TFC membrane, which reached the 2008 Robeson upper bound. It provides a candidate membrane material for O2/N2 efficient separation in moderate conditions.

New low-cost ultrafiltration membrane made from purified natural clays for direct Red 80 dye removal

This work aims to develop novel ceramic ultrafiltration membranes made from purified natural Moroccan clays. Two raw clays namely Clay A (smooth aspect) and Clay B (rough aspect) were purified via physicochemical treatment. Chemical and mineralogical characterizations demonstrated that obtained purified clays are richer in clayey minerals such as smectite, kaolinite and illite. Thin selective layer was deposed on pozzolan support via spin-coating method using purified clay suspensions and sintered at 800 °C. Prepared membranes were deeply investigated using scanning electron microscopy, pore size, water permeability, and antifouling characterizations. As results, the average pore size is found to be 75 and 90 nm respectively for Clay A and Clay B membranes while the permeability is equal to 14.7 and 16.4 L/h.m2.bar respectively for Clay A and Clay B membranes. The obtained membranes were applied for tangential filtration of Direct Red 80 solution with concentration of 50 ppm under pressure of 3 bar. Experimental results demonstrate that dye rejection could achieve a value of 99 and 97% respectively for Clay A and Clay B membranes. Based on promising filtration results, it can be suggested that prepared UF membranes could be efficiently applied for dyes removal from colored wastewater generated from textile industries.