Pervaporation Separation Performance Research Articles

Mixed matrix membranes consisting of PDMS and IL@MoS2 for enhancing 2-phenylethanol pervaporation separation

The MoS2-based mixed matrix membranes (MMMs) exhibited excellent pervaporation separation for aromatic compounds, but the narrow interlayer spacing and few affinity sites in MoS2 limited the simultaneous improvement in the total flux and separation factor. Therefore, constructing 2-PE transport channels and affinity sites in MMMs is of significant importance to improve the pervaporation separation performance. Herein, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (IL) was intercalated into the interlayer of the molybdenum disulfide (MoS2) under electrostatic and concentration diffusion interactions to obtain IL@MoS2. Then, IL@MoS2 was incorporated into polydimethylsiloxane (PDMS) to prepare MMMs for efficient 2-PE separation, which had good miscibility with polymer matrix. The total flux, separation factor and pervaporation separation index of as-prepared MMMs reached 1466 g m−2 h−1, 33 and 47,571 g m−2 h−1, separately, which increased by 26 %, 31 % and 44 % compared with that of PDMS embedding with MoS2. This is because IL@MoS2 in MMMs not only can afford 2-PE transport channels, but also provide 2-PE affinity sites due to the hydrogen bonds and π-π interactions, which promotes the solubility of 2-PE in MMMs. When the concentration of maltol increased to 1500 ppm in 2-PE aqueous solution, the 2-PE flux and separation factor of 2-PE/water only decreased by 23 % and 26 %, revealing that MMMs had good 2-PE selectivity in 2-PE/maltol/water mixture. In addition, it displayed exceptional durability during 168 h testing, demonstrating that this membrane had a good application prospect for 2-PE separation.

Synthesis optimization and separation mechanism of ZSM-5 zeolite membranes for pervaporation dehydration of organic solvents

Pervaporation (PV), as an energy-efficient mixture separation technology, plays an important role in the chemical industry. In this work, no organic templates were needed to produce high-performance ZSM-5 membranes with an extremely low Si/Al ratio of 3.3 on α-Al2O3 tubular supports using 100 nm nanoseeds. The effects of preparation parameters on the crystalline phase structures, micromorphologies, and PV separation performance of ZSM-5 membranes were comprehensively investigated. The results revealed that the Si/Al ratio of gels significantly affected both the Si/Al ratio and the crystal orientation of the final ZSM-5 membrane. The optimized ZSM-5 membrane with a thickness of 1.8 μm was utilized to dehydrate various organic solvents via PV, and the influence of the operating parameters on PV dehydration performance was evaluated and is described herein. Furthermore, the permeation behaviors of single gases and PV were examined using permeate molecules within a similar size range to reveal the PV mechanism of the ZSM-5 membrane. The results demonstrated that gas permeation followed Knudsen diffusion, while PV permeation was decreased with decreases in the affinity of molecules, revealing an adsorption-diffusion mechanism that dominated PV dehydration through the ZSM-5 membrane. Moreover, the as-synthesized ZSM-5 membrane had good water permselectivity for water/acetone (e.g., total flux = 1.03 kg/(m2 h), α = 307) and for water/isopropanol (e.g., total flux = 1.49 kg/(m2 h), α = 1070) mixtures compared with other membranes reviewed in the literature. The synthesized ZSM-5 membrane also exhibited excellent reproducibility, high stability, and attractive PV separation performance, demonstrating its significant potential application in the PV dehydration of organic solvents.

Hydrophobic enrichment-induced augmentation of NH2-UiO-66 particle interactions for enhanced pervaporation performance of polydimethylsiloxane membrane

BackgroundIn this research, we aimed to improve the hydrophobic property of NH2-UiO-66 particles by palmitoyl chloride (PC) modification. PC-UiO-66 particles were mixed in the selective layer of PDMS (polydimethylsiloxane)-PVDF (Polyvinylidene fluoride) composite membrane for organo-selective pervaporation. MethodsWe effectively preserved conspicuous crystallinity and high porosity during a conversion from hydrophilic to hydrophobic MOF, as confirmed by XRD and BET studies. The successful incorporation of palmitoyl long alkyl chains into PC-UiO-66 was verified through FTIR, XPS, and EDS studies. PC-UiO-66 particles exhibited an excellent dispersion in PDMS matrix due to a strong interfacial polymer-MOF interaction observed in FESEM and AFM studies. An organophilic pervaporation separation performance of pristine PDMS, NH2-UiO-66/PDMS, and PC-UiO-66/PDMS membranes coated on PVDF support was evaluated for ethanol/water, IPA/water, and 1,5 PDO/IPA feed solution. Significant findingsThe results demonstrated that adding PC-UiO-66 particles significantly improved the separation performance of PC-UiO-66/PDMS membranes, achieving the highest selectivity compared to pristine PDMS and NH2-UiO-66/PDMS membranes.

Mussel-inspired modification of 2D MoS2 to construct a hybrid nanocomposite membrane with enhanced pervaporation dehydration of isopropanol

In this work, a thin-film nanocomposite (TFN) membrane was constructed using a hybrid polydopamine (PD)-MoS2 (MoS2@PD) filler for pervaporation dehydration of isopropanol. The exfoliated MoS2 was first modified through bio-inspired coating of PD. The resulting MoS2@PD with different weight ratio with respect to PEI was then deposited into the hydrolyzed polyacrylonitrile support through pressure-assisted filtration, followed by crosslinking with trimesoyl chloride. Characterization experiments were performed with the membranes using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy, X-Ray Photoelectron Spectroscopy, Energy-Dispersive X-ray Spectroscopy, Field Emission Scanning Electron Microscopy, Atomic Force Microscopy, and water contact angle analyses. The PD serves as a bridging agent between MoS2 and the crosslinked PEI, enhancing the membrane’s physicochemical properties, including surface morphology and hydrophilicity. For membrane performance on pervaporation dehydration of 70/30 wt% isopropanol/water mixture at 25 °C, the addition of MoS2@PD led to a simultaneous increase in permeation total flux and water content in the permeate. Notably, MoS2@PD0.3-TFN membrane demonstrated a permeation flux of 2870.10 g∙m−2∙h−1 and 0.86/99.14 wt% isopropanol/water permeate mixture. The membrane also maintained stable performance under varying feed concentration, feed temperature, and long-term operations. This study contributes valuable insights into the development of MoS2-based membrane with enhanced pervaporation separation performance.

Separating 2-phenylethanol from aqueous solution by mixed matrix composite membranes based on beta-cyclodextrin metal organic frameworks

Natural 2-phenylethanol (2-PE) is a spice with the rose-like fragrance and non-toxicity to human, whose classical separation technique from the plants has faced great challenge owing to high energy consumption, chemical engineering safety and environmental pollution issue. Herein, the mixed matrix composite membranes (MMCMs) for 2-PE pervaporation separation from aqueous solution were engineered by incorporating beta-cyclodextrin metal organic frameworks (β-CD-MOFs) with a large amount of hydroxyl groups and hydrophobic cavities into the polydimethylsiloxane (PDMS) matrix. The as-prepared MMCMs exhibited excellent 2-PE pervaporation separation performance with the permeation total flux, separation factor, and pervaporation separation index of 1186 g m−2 h−1, 21.3 and 24076 g m−2 h−1, respectively, which increased by 25.8 %, 129.0 % and 208.6 % compared with that of the pristine one, outperforming MMCMs embedding with other fillers, when 2-PE concentration in aqueous solution is 6000 ppm. This can be explained by the fact that the hydrogen bonding and hydrophobic interaction between β-CD-MOFs and 2-PE improves 2-PE dissolution in the membrane, thus enhancing the 2-PE solubility selectivity in MMCMs. Thus, MMCMs had specific recognition for 2-PE over a spice maltol, whose 2-PE flux and the 2-PE/water separation factor only reduced by 15.0 % and 37.6 % respectively, when maltol concentration increased to 2000 ppm in 6000 ppm of 2-PE aqueous solution. Besides, resultant MMCMs showed long-term stability for over 140 h with the average permeation total flux of 1317 g m−2 h−1 and the separation factor of 21.8.

Unlocking complex chemical and morphological transformations during thermal treatment of O-hydroxyl-substituted polyimide of intrinsic microporosity: Impact on ethanol/cyclohexane separation

In this work, we investigated the pervaporation separation performance of an ethanol – cyclohexane mixture using a thin-film composite membrane based on a heat-treated, o-hydroxyl-substituted polyimide of intrinsic microporosity (PIM-6FDA-OH). We report in detail the complex chemical and structural transformations that are associated with the development of thermally-rearranged (TR, 400–450 °C), and carbon molecular sieve (CMS) membranes (>500 °C). These transformations strongly affect the affinity-related (e.g. swelling behavior) and morphology-related (e.g. microporosity) properties of the TR and CMS membrane materials which translate into a complex molecular-level separation behavior toward an organic solvent mixture during pervaporation. We show that excellent separation performance (total flux ∼ 4 kg/m2h and ethanol/cyclohexane separation factor of ∼1250) can be achieved after precise thermal treatment at the onset of the CMS formation. In addition, we highlight the unique property of pervaporation where, in contrast to liquid solvent permeation, the downstream side of the membrane remains essentially dry due to exposure to high vacuum. As a result, a sharp molecular cut-off can be achieved within this dry downstream region of the membrane despite considerable overall swelling/penetrant concentration in the upstream region of the membrane.

Metal-covalent organic framework nanosheets engineered facilitated transport membranes for toluene/n-heptane separation

Facilitated transport membranes is a promising strategy to fabricate efficient separation membranes for aromatic/aliphatic mixtures. However, building up selective channels with uniformly distributed facilitated transport sites is still challenging. In this study, Cu-TAPB-COF (CuCOF) nanosheets, a kind of metal-covalent organic frameworks (MCOFs), were synthetized and introduced into poly (ether-block amide) (Pebax®2533) matrix to construct facilitated transport membranes for toluene/n-heptane mixtures. As the aromatic skeleton linked by covalent interaction, CuCOF could provide continuous low mass transfer resistance channel. And Cu(I) exist in skeleton could serve as uniformly distributed facilitated transport sites and maintain a long-term stability. The resulting membrane exhibited a higher adsorption selectivity and lower swelling degree compared with pure Pebax membrane. The membrane exhibited high pervaporation separation performance for 50 wt% toluene/n-heptane mixture. When the filling contents of CuCOF was 2.0 wt%, the membrane achieved a permeation flux of 937 g m−2 h−1 and the separation factor of 4.7.

Molecular Simulation for Guiding the Design and Optimization of Mixed Matrix Membranes (MMMs) in the Pervaporation Process

Molecular simulation has been used extensively in the study of pervaporation membranes as a new economical and environmentally friendly research method. In this paper, A-SiO2/PDMS-PTFE mixed matrix membranes (MMMs) were prepared by molecular-simulation-guided experiments to achieve the separation of dimethyl carbonate/methanol (DMC/MeOH)) azeotropes. The interaction energy, X-ray diffraction pattern mean square displacement, and density field between PDMS and inorganic particles were analyzed by molecular dynamics simulations. The dissolution and diffusion processes of the DMC/MeOH azeotropes system in the MMM were simulated, and the surface-silylated silica (A-SiO2) with relatively better performance was screened. Based on the simulation results, A-SiO2/PDMS-PTFE MMMs were prepared by the coblending method, and the pervaporation separation performance of MMM membranes for DMC/MeOH azeotropes with different A-SiO2 loadings was investigated. When the A-SiO2 loading was 15 wt %, the separation factor of DMC/MeOH azeotropes at 50 °C was 4.74 and the flux was 1178 g m-2 h-1, which was consistent with the expected results of the simulation. The MMMs showed good stability in pervaporation over a period of up to 120 h. This study demonstrates that molecular simulations can provide a viable means for pretest screening and validation of experimental mechanisms, and to a certain extent, guide the design and optimization of pervaporation membranes.

Sub-nanometer scale tailoring of the microstructures of composite organosilica membranes for efficient pervaporation of toluene/n-heptane mixtures

Amorphous organosilica-based membranes are of enormous potential for pervaporation separation of organic mixtures, however, engineering organosilica membranes with the on-demand pore size and functionality for precise molecular sieving still remains a challenge. Herein, as a proof-of-concept, we proposed a facile and novel co-condensation strategy by pairing the biphenyl-bridged organosilica precursor (BTESBP) with another organosilica precursor (PhTES) equipped with a phenyl pendant group for efficient pervaporation of aromatic/aliphatic mixtures. It was demonstrated that the strong aromatic π-π interactions between BTESBP and PhTES as well as the steric hindrance effect of PhTES allowed the tailoring of membrane pore size at the sub-nano scale, and enhanced the accessibility of biphenyl groups to aromatic hydrocarbons. At the optimal BTESBP/PhTES mass ratio of 98/2, the resulting BTESBP/PhTES composite organosilica membrane achieved superior toluene/n-heptane pervaporation separation performance with a total flux surpassing 1 kg m−2 h−1 and a separation factor of 8–10 for a 50 wt% toluene/n-heptane feed mixture. Hopefully, this study can stimulate the rethinking of the design principles for composite organosilica membranes and the subsequent development of advanced membranes for energy-efficient pervaporation of organic mixtures.

Surface-modified silicalite-1-filled PDMS membranes for pervaporation dehydration of trichloroethylene.

In this study, the impact of silane coupling agents, namely 3-aminopropyltrimethoxysilane (APTMS), trimethylchlorosilane (TMCS), and 1,1,3,3-tetramethyldisilazane (TMDS), on the hydrophobicity of silicalite-1 zeolite was investigated to enhance the pervaporation separation performance of mixed matrix membranes (MMMs) for trichloroethylene (TCE). The hydrophobicity of TMCS@silicalite-1 and TMDS@silicalite-1 particles exhibited significant improvement, as evidenced by the increase in water contact angle from 96.1° to 101.9° and 109.1°, respectively. Conversely, the water contact angle of APTMS@silicalite-1 particles decreased to 85.2°. Silane-modified silicalite-1 particles were incorporated into polydimethylsiloxane (PDMS) to prepare mixed matrix membranes (MMMs), resulting in a significant enhancement in the adsorption selectivity of trichloroethylene (TCE) on membranes containing TMCS@silicalite-1 and TMDS@silicalite-1 particles. The experimental findings demonstrated that the PDMS membrane with a TMDS@silicalite-1 particle loading of 40 wt% exhibited the most favorable pervaporation performance. Under the conditions of a temperature of 30 °C, a flow rate of 100 mL min-1, and a vacuum degree of 30 kPa, the separation factor and total flux of a 3 × 10-7 wt% TCE aqueous solution were found to be 139 and 242 g m-2 h-1, respectively. In comparison to the unmodified silicalite-1/PDMS, the separation factor exhibited a 44% increase, while the TCE flux increased by 16%. Similarly, when compared to the pure PDMS membrane, the separation factor showed an 83% increase, and the TCE flux increased by 20%. These findings provide evidence that the hydrophobic modification of inorganic fillers can significantly enhance the separation performance of PDMS membranes for TCE.

Breakthroughs on tailoring membrane materials for ethanol recovery by pervaporation

• Mixed matrix membranes (MMMs) with well-designed membrane structures may provide both high permeability and membrane selectivity to break trade-off effect due to the better control over physi-/chemical micro-environment and cavity/pore size as well as size distribution. • Fillers should be orderly arranged in polymer matrix and form continuous transport channels for ethanol to full play the synergistic effect of polymer and fillers. • Building firm bonding interactions between filler and polymer is one of the most promising methods to strengthen the PV performance of MMMs. • The development of bioinspired materials and structures provides enlightening ideas for the construction of ethanol perm-selective membranes. Bioethanol, as a clean and renewable fuel, has gained increasing attention due to its major environmental benefits. Pervaporation (PV) is a promising and competitive technique for the recovery of ethanol from bioethanol fermentation systems due to the advantages of environmental friendliness, low energy consumption and easy coupling with fermentation process. The main challenge for the industrial application of ethanol perm-selective membranes is to break the trade-off effect between permeability and selectivity. As membrane is the heart of the pervaporation separation process, this article attempts to provide a comprehensive survey on the breakthroughs of ethanol perm-selective PV membranes from the perspectives of tailoring membrane materials to enhance PV separation performance. The research and development of polymeric and organic/inorganic hybrid membranes are reviewed to explore the fundamental structure-property-performance relationships. It is found that mixed matrix membranes with well-designed membrane structures offer the hope of better control overphysi-/chemical micro-environment and cavity/pore size as well as size distribution, which may provide both high permeability and membrane selectivity to break the trade-off effect. The tentative perspective on the possible future directions of ethanol perm-selective membranes is also briefly discussed, which may provide some insights in developing a new generation of high-performance PV membranes for ethanol recovery.

Poly(vinyl alcohol)/carbon nanotube (CNT) membranes for pervaporation dehydration: The effect of functionalization agents for CNT on pervaporation performance

Polymeric membrane-based pervaporation separation for desalination of salty water and dehydration from water/organic solvent mixtures is studied. In this work surface-functionalized carbon nanotubes (CNTs) are used to build up water-conduction pathways in poly(vinyl alcohol) (PVA) membranes. For probing the effect of functionalization agents for CNT on pervaporation separation performance, 4 agents, including PVA, polyethylenimine, lignin, and cellulose nanocrystal, have been included in the studies. The hydrophilicity of the functionalization agents, providing strong interaction between the functionalized CNT surfaces and water molecules, plays a critical role on construction of water-conduction pathways in the PVA/functionalized CNT membranes. Small amount of functionalized-CNTs (about 0.03 wt%) have exhibited significant effects on enhancing the permeation fluxes of the membranes. Among the functionalized CNTs, PVA-CNT shows the highest performance on enhancing the permeation fluxes of the corresponding membranes for desalination on a feeding solution of 3.5 wt% NaCl(aq). On the other hand, for dehydration on water/alcohol mixtures, ozonized lignin-functionalized CNTs are most effective for membrane modification. For a 70 wt% ethanol aqueous solution at 25 °C, the PVA/lignin-CNT membrane possessing 0.03 wt% of lignin-CNT exhibits a flux of 880 g m−2 h−1, compared to the value of 565 g m−2 h−1 found with the neat PVA membrane. The water concentrations of the permeated liquids for both membranes are above 99.95 wt%, corresponding to water separation factors above 4464. The increased fluxes could be attributed to the enhanced molecule mobility associating to the CNT-based water conduction pathways.

Vacuum-Assisted Interfacial Polymerization Technique for Enhanced Pervaporation Separation Performance of Thin-Film Composite Membranes.

In this work, thin-film composite polyamide membranes were fabricated using triethylenetetramine (TETA) and trimesoyl chloride (TMC) following the vacuum-assisted interfacial polymerization (VAIP) method for the pervaporation (PV) dehydration of aqueous isopropanol (IPA) solution. The physical and chemical properties as well as separation performance of the TFCVAIP membranes were compared with the membrane prepared using the traditional interfacial polymerization (TIP) technique (TFCTIP). Characterization results showed that the TFCVAIP membrane had a higher crosslinking degree, higher surface roughness, and denser structure than the TFCTIP membrane. As a result, the TFCVAIP membrane exhibited a higher separation performance in 70 wt.% aqueous IPA solution at 25 °C with permeation flux of 1504 ± 169 g∙m−2∙h−1, water concentration in permeate of 99.26 ± 0.53 wt%, and separation factor of 314 (five times higher than TFCTIP). Moreover, the optimization of IP parameters, such as variation of TETA and TMC concentrations as well as polymerization time for the TFCVAIP membrane, was carried out. The optimum condition in fabricating the TFCVAIP membrane was 0.05 wt.% TETA, 0.1 wt% TMC, and 60 s polymerization time.

Acid-reinforced ionic cross-linking of sodium alginate/polyamidoamine dendrimer blended composite membranes for isopropanol dehydration through pervaporation

Extreme swelling of hydrophilic polymer such as sodium alginate in aqueous liquid mixture separation processes has always been a problem that needs to be resolved. Herein, the ionic interactions between polyamidoamine (PAMAM) dendrimers and sodium alginate (SA) were improved by using simple aqueous acidic solution after obtaining the dense composite membranes. The zero generation PAMAM dendrimer (G0) used has four terminal primary amine reactive groups (P4). The acid-reinforced ionic cross-linked (ARIC) membranes gave an impressive water stability even at high water content in feed of 90 wt% during the separation process. The composite membranes were characterized accordingly for their chemical and physical properties. Also, the efficiency of the ARIC process was evaluated by separating alcohol/water mixtures through pervaporation at varying feed concentration and temperature. Impressively, the membranes treated with sulfuric acid resulted to a smaller free volume size compared to hydrochloric acid revealed by positron annihilation spectroscopy (PAS). This means that a lower swelling degree for the sulfuric acid-treated membranes giving better separation efficiency even at high water feed composition. The best pervaporation separation performance was observed in separating 70/30 wt% isopropanol/H2O aqueous solution at 55 °C. It has a permeation flux of 6.59 kg m−2 h−1 and a 99.97 wt% water content in permeate. The membrane, SA-P4-H2SO4/PVDF also exhibited good stability for 552 h maintaining a water concentration in permeate above 97 wt%.

Machine Learning-Enabled Prediction and High-Throughput Screening of Polymer Membranes for Pervaporation Separation.

Pervaporation (PV) is considered as a robust membrane-based separation technology for liquid mixtures. However, the development of PV membranes is impeded largely by the lack of adequate models capable of reliably predicting the performance of PV membranes. In this study, we collect an experimental data set with a total of 681 data samples including 16 polymers and 6 organic solvents for a wide variety of water/organic mixtures under various operating conditions. Then, two types of machine learning (ML) models are developed for prediction and high-throughput screening of polymer membranes for PV separation. Based on the intrinsic properties of polymer and solvent (water contact angle of polymer and solubility parameter of solvent) as gross descriptors, the first type accurately predicts PV separation performance (total flux and separation factor). The second type is based on the molecular representation of polymer and solvent, giving accuracy comparable to the first type, and applied to screen ∼1 million hypothetical polymers for PV separation of water/ethanol mixtures. With a threshold of 700 for the PV separation index, 20 polymers are shortlisted, with many surpassing experimental samples. Among these, 10 are further identified to be synthesizable in terms of a synthetic complexity score. The ML models developed in this study would facilitate the optimization of operating conditions and accelerate the development of new polymer membranes for high-performance PV separation.

Electrospun carboxyl‐functionalised multi‐walled carbon nanotube/poly(vinyl alcohol) asymmetric pervaporation membrane: Application and modeling

AbstractThis study focuses on the development of an asymmetric membrane comprised of an electrospun carboxyl‐functionalised multi‐walled carbon nanotube (COOH‐MWCNT)/poly (vinyl alcohol) (PVA) composite nanofibre layer on a dense PVA separation layer (MCOOH‐MWCNT). The electrospun nanofibre layer in this study acts as a “pre‐selective layer” instead of its common function as a membrane support. In addition, COOH‐MWCNT, a hydrophilic filler is integrated in the nanofibres to further enhance the membrane pervaporation separation performance. Immense improvement was observed in the pervaporation performance of the resultant asymmetric membranes in the dehydration of aqueous 1,4‐dioxane solutions, owing to the presence of the electrospun composite nanofibres as a hydrophilic layer. The resultant asymmetric membrane showed an increase of nearly 80% in water permeation flux as compared to that of the dense PVA membrane alone, and the separation factor was improved from 392.65 to 605.35. The parameters estimated using Rautenbach model showed that the dehydration of aqueous 1,4‐dioxane solutions via pervaporation is dominantly governed by sorption process. The permeation flux, transport coefficient of water and 1,4‐dioxane of the electrospun asymmetric membrane showed a good agreement in between the experimental data and those predicted using Rautenbach model.

Stable Zr-Based Metal-Organic Framework Nanoporous Membrane for Efficient Desalination of Hypersaline Water.

Treatment of hypersaline waters is a critical environmental challenge. Pervaporation (PV) desalination is a promising technique to address this challenge, but current PV membranes still suffer from challenging issues such as low flux and insufficient stability. Herein, we propose in situ nanoseeding followed by a secondary growth strategy to fabricate a high-quality stable metal-organic framework (MOF) thin membrane (UiO-66) for high-performance pervaporation desalination of hypersaline waters. To address the issue of membrane quality, a TiO2 nano-interlayer was introduced on coarse mullite substrates to favor the growth of a UiO-66 nanoseed layer, on which a well-intergrown UiO-66 selective membrane layer with thickness as low as 1 μm was finally produced via subsequent secondary growth. The PV separation performance for hypersaline waters was systematically investigated at different salt concentrations, feed temperatures, and long-term operation in different extreme chemical environments. Besides having nearly complete rejection (99.9%), the UiO-66 membrane exhibited high flux (37.4 L·m-2·h-1) for hypersaline waters, outperforming current existing zeolite and MOF membranes. The membrane also demonstrated superior long-term operational stability under various harsh environments (hypersaline, hot, and acidic/alkaline feed water) and mild fouling behavior. The rational design proposed in this study is not only applicable for the development of a high-quality UiO-66 membrane enabling harsh hypersaline water treatment but can also be potentially extended to other next-generation nanoporous MOF membranes for more environmental applications.

Hydrophobic Two-Dimensional MoS2 Nanosheets Embedded in a Polyether Copolymer Block Amide (PEBA) Membrane for Recovering Pyridine from a Dilute Solution.

A two-dimensional molybdenum disulfide (MoS2) nanosheet, as a new type of inorganic material with high hydrophobicity and excellent physicochemical stability, holds great application potential in the preparation of a high separation performance organic–inorganic hybrid membrane. In this work, high hydrophobic MoS2 was embedded in hydrophobic polyether copolymer block amide (PEBA) to prepare PEBA/MoS2 organic–inorganic hybrid membranes. The structure, morphology, and hydrophobicity of the hybrid membrane were characterized by scanning electron microscopy, thermogravimetric analysis, contact angle goniometry, X-ray diffraction, infrared spectroscopy analysis, and atomic force microscopy. The effect of embedding of MoS2 on the swelling degree and pervaporation separation performance of the PEBA/MoS2 hybrid membrane was studied with a 1.0 wt % pyridine dilute solution. The results indicated that with increasing the MoS2 content, the separation factor of PEBA/MoS2 increased first and then decreased, while it showed a downward trend in the permeation flux. When the MoS2 content in the PEBA/MoS2 hybrid membrane was 10.0 wt %, the permeation flux was 83.4 g m–2 h–1 (decreased by 21.5% compared with the pure PEBA membrane), and the separation factor reached a maximum value of 11.11 (increased by 37.6% compared with the pure PEBA membrane). Meanwhile, the effects of feed temperature on the pervaporation separation performance of PEBA/MoS2 hybrid membranes were also studied. In addition, as the PEBA/MoS2 hybrid membrane has excellent thermal stability, it is expected to be a promising material for recovering pyridine from wastewater.

Pervaporation dehydration of bio-fuel (n-butanol) by dry thermal treatment membrane

In the present investigation, laboratory synthesized graphene oxide (GO) as a nano-filler was used in polyetherimide (PEI) flat-sheet membranes (PM). The PEI flat-sheet membrane was fabricated through a dry-thermal treatment (DTT) method. The effects of fabrication method were investigated on polyetherimide-GO membrane prepared by dry-thermal treatment (PMDTT). The morphological structure was investigated via different characterization; Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), contact angle measurement and Raman spectra. The results indicated that, the hybrid PMDTT membrane displayed reasonably better pervaporation separation performance in comparison to neat PMDTT membranes. The concentrations of water at the permeate side of hybrid and neat PMDTT membrane were 99.3 and 90.9 wt.%, respectively. Hybrid membranes showed a 78.3% enhanced permeation rate. Enhancement of pervaporation property of hybrid PMDTT membrane could be ascribed mainly due to the presence of graphene oxide in the dense top layer. Overall, the blending of graphene oxide in hybrid PMDTT membranes could be a promising approach for enhancing the pervaporation properties of the membranes.

Preparation of hybrid membranes by incorporating hydrophilic UiO-66 nanoparticles for high-performance pervaporation dehydration of aprotic solvents

Hydrophilic UiO-66 crystals with superior water adsorption ability were synthesized and incorporated into the polyimide (PI) membrane for efficient aprotic solvent separation via pervaporation. The effect of the different UiO-66 addition in the pyromellitic dianhydride (PMDA)-2, 2-bis[4-(4-amlnophenoxy)phenyl]propane (BAPP)-based PI membrane on the membrane structure, thermal stability, surface hydrophilicity, solvent-resistant, and pervaporation performance was systematically studied. The UiO-66/PI hybrid membranes with small amount content (2 wt%) exhibited high hydrophilicity and excellent swelling resistance due to the superb dispersion benefiting from the excellent complexation of UiO-66 and PI chain. The effects of operational variables such as operating temperature and concentration of feed solution on the pervaporation separation performance of the hybrid membranes with different UiO-66 loadings were investigated. When the mass fraction of UiO-66 was 2 wt%, the hybrid membranes show the permeation flux of 109.7 and 57.1 g/(m2h) and separation factor of 34.1 and 133.9, respectively, for DMF/H2O and DMAc/H2O systems.