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Composite polymer membranes were obtained using the so-called dry phase inversion and were used for desalination of diluted saline water solutions by pervaporation (PV) method. The tests used a two-layer backing, porous, ultrafiltration commercial membrane (PS20), which consisted of a supporting polyester layer and an active polysulfone layer. The active layer of PV membranes was obtained in an aqueous environment, in the presence of a surfactant, by cross-linking a 5 wt.% aqueous solution of polyvinyl alcohol (PVA)—using various amounts of cross-linking substances: 50 wt.% aqueous solutions of glutaraldehyde (GA) or citric acid (CA) or a 40 wt.% aqueous solution of glyoxal. An ethylene glycol oligomer (PEG 200) was also used to prepare active layers on PV membranes. Witch its help a chemically cross-linked hydrogel with PVA and cross-linking reagents (CA or GA) was formed and used as an active layer. The manufactured PV membranes (PVA/PSf/PES) were used in the desalination of water with a salinity of 35‰, which corresponds to the average salinity of oceans. The pervaporation method was used to examine the efficiency (productivity and selectivity) of the desalination process. The PV was carried at a temperature of 60 °C and a feed flow rate of 60 dm3/h while the membrane area was 0.005 m2. The following characteristic parameters of the membranes were determined: thickness, hydrophilicity (based on contact angle measurements), density, degree of swelling and cross-linking density and compared with the analogous properties of the initial PS20 backing membrane. The physical microstructure of the cross-section of the membranes was analyzed using scanning electron microscopy (SEM) method.

Organic–inorganic hybrid silica materials, incorporating an organic group bridging two silicon atoms, have demonstrated great potential in creating membranes with excellent permselectivity. Yet, the large-scale production of polymer-supported flexible hybrid silica membranes has remained a significant challenge. In this study, we present an easy and scalable approach for fabricating these membranes. By employing a sol–gel ultrasonic spray process with a single-pass method, we deposited a thin and uniform hybrid active layer onto a porous polymer substrate. We first optimized the deposition conditions, including substrate temperature, the binary solvent ratio of the silica sol, and various ultrasonic spray parameters. The resulting flexible hybrid silica membranes exhibited exceptional dehydration performance for isopropanol (IPA)/water solutions (IPA: 90 wt%) in the pervaporation process, achieving a water flux of 0.6 kg/(m2 h) and a separation factor of around 1300. This work demonstrates that the single-pass ultrasonic spray method is an effective strategy for the large-scale production of polymer-supported flexible hybrid silica membranes.

The separation of a toluene/methanol/water ternary mixture is a difficult task due to the toluene/water and toluene/methanol azeotropes. In this article, low-energy pervaporation is proposed for the separation of the ternary azeotrope toluene–methanol–water. This work investigates the effects of feed temperature, feed flow rate, and vacuum on pervaporation and compares the energy consumption of pervaporation with that of distillation. The results showed that at the optimized flow rate of 50 L/h and a permeate side vacuum of 60 kPa at 50 °C, the water and methanol content in the permeate was about 63.2 wt.% and 36.8 wt.%, respectively, the water/ methanol separation factor was 24.04, the permeate flux was 510.7 g/m2·h, the water content in the feed out was reduced from 2.5 wt.% to less than 0.66 wt.%, and the dehydration of toluene methanol could be realized. Without taking into account the energy consumption of pumps and other power equipment, pervaporation requires an energy consumption of 43.53 kW·h to treat 1 ton of raw material, while the energy consumption of distillation to treat 1 ton of raw material is about 261.5 kW·h. Compared to the existing distillation process, the pervaporation process consumes much less energy (about one-sixth of the energy consumption of distillation). There is almost no effect on the surface morphology and chemical composition of the membrane before and after use. The method provides an effective reference for the dehydration of organic solvents from ternary mixtures containing toluene/methanol/water.

The performance of a new commercial polyvinyl alcohol (PVA) membrane (PERVAPTM 4100HF) was investigated and compared with a standard membrane (PERVAPTM 4100) for the dehydration of isopropanol (isopropyl alcohol) with an azeotropic point using pervaporation process. Both membranes were also characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and contact angle (CA) goniometer. The results showed that the PERVAP™ 4100HF was thinner (1–1.5 μm) and had a lower degree of cross-linking than the PERVAP™ 4100HF (2–3 μm). The effect of the feed water concentration and operating temperature on the membranes separation performance in terms of the permeation flux, separation factor, selectivity, and permeance was investigated. The water permeates in the PERVAP™ 4100HF (∼3350 GPU) was seven times higher than that in PERVAP™ 4100 (∼463 GPU) at 70 °C and for 7 wt.% of water concentration in the feed. The water/isopropanol selectivity of the new membrane under these operating conditions was very high (∼17,000). The total permeation flux of water and isopropyl alcohol (IPA) was increased with the feedwater concentration (0.0690–1.0275 and 0.0079–0.6384 kg/m2.hr) for PERVAP™ 4100HF and PERVAP™ 4100, respectively with feed water concentration increased from 7 to 18 wt.%. The temperature dependence of the pervaporation behaviors was investigated in detail in terms of the Arrhenius activation energy. The effect of the feedwater concentration on the Arrhenius activation energy was also studied to evaluate the mass transfer across the membrane under other operating conditions, such as high temperatures and low feedwater concentrations. The new membrane PERVAP™ 4100HF exhibited the best dehydration properties at water concentrations in the azeotropic region and below, making it possible to pervaporate even at low feedwater concentrations.

Pervaporation is a membrane-based process used for the separation of liquid mixtures. As this membrane process is governed by the differences in the sorption and diffusivities of separated components, close boiling mixtures and azeotropic mixtures can effectively be separated. The dehydration of ethanol is the most common application of hydrophilic pervaporation. The pilot scale properties of hydrophilic composite poly(vinyl alcohol) PVA membrane (PERVAPTM 2200) in contact with wet raw bioethanol are presented. The wet raw bioethanol was composed of ethanol (82.4–89.6 wt%), water (5.9–8.5 wt%), methanol (2.3–6.9 wt%), cyclohexane (0.2–2.4 wt%), higher alcohols (0.2–1.3 wt%), and acetaldehyde (0.004–0.030 wt%). All experiments were performed using a SULZER ECO-001 plant equipped with a 1.5 m2 membrane module. The efficiency of the dehydration process (i.e., membrane selectivity, permeate flux, degree of dehydration) was discussed as a function of the following parameters: the feed temperature, the feed composition, and the feed flow rate through the module. It was found that the low feed flow rate influenced the dehydration efficiency as the enthalpy of evaporation caused a high temperature drop in the module (around 25 °C at a feed flow rate equal to 5 kg h−1). The separation coefficient during pervaporation was in the range of 600–1200, depending on the feed composition. The increase in temperature augmented the permeation flux and shortened the time needed to reach the assumed level of dehydration. It was revealed that dehydration by pervaporation using ECO-001 pilot plant is an efficient process, allowing also to investigate the influence of various parameters on the process efficiency.

Pervaporation is an energy-efficient alternative to conventional distillation for water/alcohol separations. In this work, a novel CHA zeolite membrane with an increased Si/Al ratio was synthesized in the absence of organic templates for the first time. Nanosized high-silica zeolite (SSZ-13) seeds were used for the secondary growth of the membrane. The separation performance of membranes in different alcohol–aqueous mixtures was measured. The effects of water content in the feed and the temperature on the separation performance using pervaporation and vapor permeation were also studied. The best membrane showed a water/ethanol separation factor above 100,000 and a total flux of 1.2 kg/(m2 h) at 348 K in a 10 wt.% water–ethanol mixed solution. A membrane with high performance and an increased Si/Al ratio is promising for the application of alcohol dehydration.

Herein, we report on the performance of a hybrid organic-ceramic hydrophilic pervaporation membrane applied in a vacuum membrane distillation operating mode to desalinate laboratory prepared saline waters and a hypersaline water modeled after a real oil and gas produced water. The rational for performing “pervaporative distillation” is that highly contaminated waters like produced water, reverse osmosis concentrates and industrial have high potential to foul and scale membranes, and for traditional porous membrane distillation membranes they can suffer pore-wetting and complete salt passage. In most of these processes, the hard to treat feed water is commonly softened and filtered prior to a desalination process. This study evaluates pervaporative distillation performance treating: (1) NaCl solutions from 10 to 240 g/L at crossflow Reynolds numbers from 300 to 4800 and feed-temperatures from 60 to 85 °C and (2) a real produced water composition chemically softened to reduce its high-scale forming mineral content. The pervaporative distillation process proved highly-effective at desalting all feed streams, consistently delivering

Graphene oxide (GO) with its atomic thickness and abundant functional groups holds great potential in molecular-scale membrane separation. However, constructing high-speed and highly selective water transport channels within GO membranes remains a key challenge. Herein, sulfonato calix[n]arenes (SCn) molecules with a cavity structure, hydrophilic entrance, and hydrophobic wall were incorporated into GO interlayer channels through a layer-by-layer assembly approach to facilitate water permeation in a water/ethanol separation process. The hydrophilic entrance enables preferential access of water molecules to the cavity over ethanol molecules, while the high hydrophobicity of the cavity wall confers low resistance for water diffusion. After incorporating SCn molecules, the membrane shows a remarkable increase in the water/ethanol separation factor from 732 to 1260, while the permeate flux also increases by about 50%. In addition, the strong electrostatic interactions between the building blocks endow the membrane with excellent swelling resistance even under a high water content. This work provides an effective strategy of constructing high-efficiency water transport channels in membrane.

Membrane-based pervaporation (PV) is highly efficient and energy-saving, and is poised to emerge as a promising technology for recovering biofuels from aqueous solutions. In this study, we prepared two versions of zeolite membranes, randomly oriented and highly (h0h)-oriented silicalite-1, with similar thicknesses on α-alumina tubes, and performed the first-reported systematic comparison of their PV performances in recovering organic solvents such as methanol, ethanol, acetone, n-propanol, isopropanol, and n-butanol from water. The contribution of the intrinsic properties of these membranes to PV was explored through permeance and selectivity analysis. The highly (h0h)-oriented membrane exhibited a significantly higher level of PV performance. In addition, the permeation behavior of PV and single-gas molecules through the highly (h0h)-oriented membranes was investigated, along with the influence that operating conditions (feed temperature and concentration) exert on PV. The results suggest that the PV permeation mechanism of organic solvent/water systems through the (h0h)-oriented silicalite-1 membranes involves a combination of adsorption-diffusion and molecular sieving. Furthermore, compared with other MFI-based membranes reported in the literature, the highly (h0h)-oriented silicalite-1 membrane demonstrated outstanding comprehensive separation performance due to its highly hydrophobic, preferentially oriented, and uniform silicalite-1 layer. For example, the separation factors for 10 wt% binary aqueous solutions of methanol, ethanol, acetone, and n-propanol were 12 at 50 °C, 32 at 70 °C, 145 at 70 °C, and 37.7 at 50 °C, respectively, with corresponding total flux values of 4.18, 2.63, 2.5, and 0.29 kg/(m2 h), respectively. These unique properties suggest its potential for PV recovery of organic solvents in sustainable chemical engineering. Figure. Schematic diagrams of the structure, pore size, and pervaporation process of (a) highly (h0h)-oriented MFI membranes and (b) randomly oriented MFI membranes with intercrystalline defects, (c) molecular size dependency of the permeance on single-gas permeation and pervaporation in organic solvent/water mixtures (water permeance was obtained from the MeOH/water mixture). [Display omitted] • A highly (h0h)-oriented silicalite-1 zeolite membrane was successfully prepared. • This is the first systematic study of (h0h)-oriented silicalite-1 membranes for PV recovery of organic solvents. • The (h0h)-oriented membrane exhibited excellent pervaporation separation performance. • The PV permeation mechanism was controlled by adsorption-diffusion and molecular sieving. [ABSTRACT FROM AUTHOR]

Mixed matrix membranes (MMMs) have shown great potential in pervaporation (PV). As for many novel membrane materials however, lab-scale testing often involves synthetic feed solutions composed of mixed pure components, overlooking the possibly complex interactions and effects caused by the numerous other components in a real PV feed. This work studies the performance of MMMs with two different types of fillers, a core-shell material consisting of ZIF-8 coated on mesoporous silica and a hollow sphere of silicalite-1, in the PV of a real fermented wheat/hay straw hydrolysate broth for the production of bio-ethanol. All membranes, including a reference unfilled PDMS, show a declining permeability over time. Interestingly, the unfilled PDMS membrane maintains a stable separation factor, whereas the filled PDMS membranes rapidly lose selectivity to levels below that of the reference PDMS membrane. A membrane autopsy using XRD and SEM-EDX revealed an almost complete degradation of the crystalline ZIF-8 in the MMMs. Reference experiments with ZIF-8 nanoparticles in the fermentation broth demonstrated the influence of the broth on the ZIF-8 particles. However, the observed effects from the membrane autopsy could not exactly be replicated, likely due to distinct differences in conditions between the in-situ pervaporation process and the ex-situ reference experiments. These findings raise significant questions regarding the potential applicability of MOF-filled MMMs in real-feed pervaporation processes and, potentially, in harsh condition membrane separations in general. This study clearly confirms the importance of testing membranes in realistic conditions.

In this study, a multi-layer pervaporation composite membrane was prepared by spray-coating a hydrophilic layer consisting of poly(allylamine hydrochloride) (PAH)/polyvinyl alcohol (PVA)/trimesic acid (BTA) onto a polyethersulfone (PES) porous substrate. The presence of amine groups facilitated the transport of water molecules, enabling the composite membrane to exhibit excellent water/ethanol separation properties. When a feed solution consisting of 90 ​wt% ethanol and 10 ​wt% water was dehydrated using the PV membrane at 70 ​°C, a flux of 1.46 ​kg ​m−2 ​h−1 with a water/ethanol separation factor of 3300 was realized. In addition, after coating a 267 ​nm silicone rubber layer on top of the membrane, the separation factor was further increased by 70.79 % to 5285, while the flux was slightly decreased by 12.33 % to 1.28 ​kg ​m−2 ​h−1. This was because the hydrophobic silicone rubber layer reduced the water swelling effect of the selective layer and hindered the permeation of ethanol-water coupling molecules, resulting in a reduction in the ethanol flux of the composite membrane and an improvement in the separation factor. This simple but effective method to improve dehydration properties was very useful for fabricating PV composite membranes.

Crystallization of active pharmaceutical ingredients is essential in pharmaceutical production. Pervaporation, a thermally-driven membrane process, has not been explored in API crystallization. Here we demonstrated PV-assisted crystallization (PVaC) for simultaneous recovery of API ortho-aminobenzoic acid (o-ABA) and pure solvent. The PERVAP 4060 made of organophilic polymer was found suitable given the reasonable flux of ethanol of 3.69 ​kg/m2/h at 45 ​°C with saturated solution and 99.9% o-ABA rejection. A parametric study showed that the membrane permeance increased with feed flow rate and temperature, but decreased with supersaturation. In the sequential PVaC, the stable form I of o-ABA was obtained with 25 ​°C PV; while with 45 ​°C PV, only metastable form II crystallized. In the simultaneous PVaC, at 0 time lag pure form II was produced; by increasing time lag, form I increased significantly. The results indicated potential routes to control polymorph formation via PVaC, providing a promising alternative for API production.

Chitosan (CS) membranes have been widely applied in water/ethanol separation via membrane-based pervaporation, but a bottleneck in the practical application always exists due to their severe swelling behavior in aqueous solution and consequently low permeation flux due to the large membrane thickness. Here, thin film composite (TFC) hollow fiber (HF) membrane with an in-situ-crosslinked ultrathin CS selective layer is developed via multiple supramolecular interaction-crosslinking strategy for efficient water/ethanol separation via pervaporation. With Fe3+-phytic acid (PhA) complex pre-deposited on the substrate, the subsequently introduced CS selective layer is in-situ crosslinked via multiple supramolecular interactions, including coordination, electrostatic, and hydrogen bonding interactions. By varying the cycle number of Fe3+/PhA assembly and the species of employed organophosphorus acid, the anti-swelling properties of the resultant TFC CS membrane is enhanced and the separation performance is maximized. The optimal TFC-CS-Fe2PhA2 membrane with two cycles of Fe3+/PhA assembly has a selective layer thickness of 60 ​nm and a corresponding ultrahigh flux of 2.87 ​kg/m2 h, coupled with a permeate water concentration of 99.5 ​wt% and good long-term stability for the dehydration of 85 ​wt% ethanol aqueous solution at 50 ​°C. The supramolecular interaction-crosslinking presented in this work provides an efficient and promising strategy for the construction of TFC CS membrane with excellent anti-swelling property and superior separation performance.

Motivated by the need for developing membranes for biofuel purification, we made pervaporation membranes by casting a polystyrene-b-polydimethylsiloxane-b-polystyrene (SDS) triblock copolymer using toluene, cyclohexane, and hexane as casting solvents. The three solvents have different affinities for each of the blocks of the SDS, which enables the creation of membranes with different nano-morphologies using the same block copolymer. These membranes were used in pervaporation experiments with butanol/water mixtures as the feed solution. We quantify the effect of morphology on butanol and water permeabilities. Poorly-ordered granular morphology, obtained from hexane-cast membranes, is optimal for selective butanol transport. Butanol permeability was a more sensitive function of morphology than water permeability. Butanol uptake measurements showed that morphology had negligible effects on solubility. Therefore, we attribute the dependence of permeability on morphology to differences in diffusivities.

Motivated by the need for developing membranes for biofuel purification, we made pervaporation membranes by casting a polystyrene-b-polydimethylsiloxane-b-polystyrene (SDS) triblock copolymer using toluene, cyclohexane, and hexane as casting solvents. The three solvents have different affinities for each of the blocks of the SDS, which enables the creation of membranes with different nano-morphologies using the same block copolymer. These membranes were used in pervaporation experiments with butanol/water mixtures as the feed solution. We quantify the effect of morphology on butanol and water permeabilities. Poorly-ordered granular morphology, obtained from hexane-cast membranes, is optimal for selective butanol transport. Butanol permeability was a more sensitive function of morphology than water permeability. Butanol uptake measurements showed that morphology had negligible effects on solubility. Therefore, we attribute the dependence of permeability on morphology to differences in diffusivities.

BackgroundBiomass pretreatment using certain ionic liquids (ILs) is very efficient, generally producing a substrate that is amenable to saccharification with fermentable sugar yields approaching theoretical limits. Although promising, several challenges must be addressed before an IL pretreatment technology can become commercially viable. One of the most significant challenges is the affordable and scalable recovery and recycle of the IL itself. Pervaporation (PV) is a highly selective and scalable membrane separation process for quantitatively recovering volatile solutes or solvents directly from non-volatile solvents that could prove more versatile for IL dehydration.ResultsWe evaluated a commercially available PV system for IL dehydration and recycling as part of an integrated IL pretreatment process using 1-ethyl-3-methylimidazolium acetate ([C2C1Im][OAc]) that has been proven to be very effective as a biomass pretreatment solvent. Separation factors as high as 1500 were observed. We demonstrate that >99.9 wt% [C2C1Im][OAc] can be recovered from aqueous solution (≤20 wt% IL) and recycled five times. A preliminary technoeconomic analysis validated the promising role of PV in improving overall biorefinery process economics, especially in the case where other IL recovery technologies might lead to significant losses.ConclusionsThese findings establish the foundation for further development of PV as an effective method of recovering and recycling ILs using a commercially viable process technology.

Constructing efficient and continuous transport pathways in membranes is a promising and challenging way to achieve the desired performance in the pervaporation process. The incorporation of various metal–organic frameworks (MOFs) into polymer membranes provided selective and fast transport channels and enhanced the separation performance of polymeric membranes. Particle size and surface properties are strongly related to the random distribution and possible agglomeration of MOFs particles, which may lead to poor connectivity between adjacent MOFs-based nanoparticles and result in low-efficiency molecular transport in the membrane. In this work, ZIF−8 particles with different particle sizes were physically filled into PEG to fabricate mixed matrix membranes (MMMs) for desulfurization via pervaporation. The micro-structures and physi-/chemical properties of different ZIF−8 particles, along with their corresponding MMMs, were systematically characterized by SEM, FT-IR, XRD, BET, etc. It was found that ZIF−8 with different particle sizes showed similar crystalline structures and surface areas, while larger ZIF−8 particles possessed more micro-pores and fewer meso-/macro-pores than did the smaller particles. ZIF−8 showed preferential adsorption for thiophene rather than n−heptane molecules, and the diffusion coefficient of thiophene was larger than that of thiophene in ZIF−8, based on molecular simulation. PEG MMMs with larger ZIF−8 particles showed a higher sulfur enrichment factor, but a lower permeation flux than that found with smaller particles. This might be ascribed to the fact that larger ZIF−8 particles provided more and longer selective transport channels in one single particle. Moreover, the number of ZIF−8−L particles in MMMs was smaller than the number of smaller ones with the same particle loading, which might weaken the connectivity between adjacent ZIF−8−L nanoparticles and result in low-efficiency molecular transport in the membrane. Moreover, the surface area available for mass transport was smaller for MMMs with ZIF−8−L particles due to the smaller specific surface area of the ZIF−8−L particles, which might also result in lower permeability in ZIF−8−L/PEG MMMs. The ZIF−8−L/PEG MMMs exhibited enhanced pervaporation performance, with a sulfur enrichment factor of 22.5 and a permeation flux of 183.2 g/(m−2·h−1), increasing by 57% and 389% compared with the results for pure PEG membrane, respectively. The effects of ZIF−8 loading, feed temperature, and concentration on desulfurization performance were also studied. This work might provide some new insights into the effect of particle size on desulfurization performance and the transport mechanism in MMMs.

Polyvinyl alcohol (PVA) pervaporation (PV) membranes have been extensively studied in the field of ethanol dehydration. The incorporation of two-dimensional (2D) nanomaterials into the PVA matrix can greatly improve the hydrophilicity of the PVA polymer matrix, thereby enhancing its PV performance. In this work, self-made MXene (Ti3C2Tx-based) nanosheets were dispersed in the PVA polymer matrix, and the composite membranes were fabricated by homemade ultrasonic spraying equipment with poly(tetrafluoroethylene) (PTFE) electrospun nanofibrous membrane as support. Due to the gentle coating of ultrasonic spraying and following continuous steps of drying and thermal crosslinking, a thin (~1.5 μm), homogenous and defect-free PVA-based separation layer was fabricated on the PTFE support. The prepared rolls of the PVA composite membranes were investigated systematically. The PV performance of the membrane was significantly improved by increasing the solubility and diffusion rate of the membranes to the water molecules through the hydrophilic channels constructed by the MXene nanosheets in the membrane matrix. The water flux and separation factor of the PVA/MXene mixed matrix membrane (MMM) were dramatically increased to 1.21 kg·m−2·h−1 and 1126.8, respectively. With high mechanical strength and structural stability, the prepared PGM-0 membrane suffered 300 h of the PV test without any performance degradation. Considering the promising results, it is likely that the membrane would improve the efficiency of the PV process and reduce energy consumption in the ethanol dehydration.

Recent years have shown a growing interest in the application of membranes exhibiting magnetic properties in various separation processes. The aim of this review is to provide an in-depth overview of magnetic membranes that can be successfully applied for gas separation, pervaporation, ultrafiltration, nanofiltration, adsorption, electrodialysis, and reverse osmosis. Based on the comparison of the efficiency of these separation processes using magnetic and non-magnetic membranes, it has been shown that magnetic particles used as fillers in polymer composite membranes can significantly improve the efficiency of separation of both gaseous and liquid mixtures. This observed separation enhancement is due to the variation of magnetic susceptibility of different molecules and distinct interactions with dispersed magnetic fillers. For gas separation, the most effective magnetic membrane consists of polyimide filled with MQFP-B particles, for which the separation factor (αrat O2/N2) increased by 211% when compared to the non-magnetic membrane. The same MQFP powder used as a filler in alginate membranes significantly improves water/ethanol separation via pervaporation, reaching a separation factor of 12,271.0. For other separation methods, poly(ethersulfone) nanofiltration membranes filled with ZnFe2O4@SiO2 demonstrated a more than four times increase in water flux when compared to the non-magnetic membranes for water desalination. The information gathered in this article can be used to further improve the separation efficiency of individual processes and to expand the application of magnetic membranes to other branches of industry. Furthermore, this review also highlights the need for further development and theoretical explanation of the role of magnetic forces in separation processes, as well as the potential for extending the concept of magnetic channels to other separation methods, such as pervaporation and ultrafiltration. This article provides valuable insights into the application of magnetic membranes and lays the groundwork for future research and development in this area.

Mixed matrix membranes (MMMs) with nano-fillers dispersed in polymer matrix have been proposed as alternative pervaporation membrane materials. They possess both promising selectivity benefiting from the fillers and economical processing capabilities of polymers. ZIF-67 was synthesized and incorporated into the sulfonated poly (aryl ether sulfone) (SPES) matrix to prepare SPES/ZIF-67 mixed matrix membranes with different ZIF-67 mass fractions. The as-prepared membranes were used for pervaporation separation of methanol/methyl tert-butyl ether mixtures. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and laser particle size analysis results show that ZIF-67 is successfully synthesized, and the particle size is mainly between 280 nm and 400 nm. The membranes were characterized by SEM, atomic force microscope (AFM), water contact angle, thermogravimetric analysis (TGA), mechanical property testing and positron annihilation technique (PAT), sorption and swelling experiments, and the pervaporation performance was also investigated. The results reveal that ZIF-67 particles disperse uniformly in the SPES matrix. The roughness and hydrophilicity are enhanced by ZIF-67 exposed on the membrane surface. The mixed matrix membrane has good thermal stability and mechanical properties, which can meet the requirements of pervaporation operation. The introduction of ZIF-67 effectively regulates the free volume parameters of the mixed matrix membrane. With increasing ZIF-67 mass fraction, the cavity radius and free volume fraction increase gradually. When the operating temperature is 40 °C, the flow rate is 50 L·h−1 and the mass fraction of methanol in feed is 15%, the mixed matrix membrane with ZIF-67 mass fraction of 20% shows the best comprehensive pervaporation performance. The total flux and separation factor reach 0.297 kg·m−2·h−1 and 2123, respectively.

Pervaporation is a membrane process that offers high separation performance and has an important potential for the treatment of saline water sources. In this study, poly(vinyl alcohol) (PVA) and PVA-SiO2 nanocomposite membranes were prepared by the solution-casting method, and pervaporative water desalination studies were carried out for synthetic seawater (35 g L-1) at 30, 40 and 50°C. Effects of the temperatures and the incorporation of SiO2 on the pervaporation performance of polymeric nanocomposite membranes were investigated. Membranes were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). In experiments conducted at 50°C, a permeate flux of 4.93 kg m-2 h-1 with a salt rejection of 99.3% were obtained. The highest salt rejection was 99.8% at temperature of 30°C. The results showed that the pervaporation performance of PVA membranes was remarkably enhanced with the incorporation of nano-SiO2 into polymeric matrix.

Gas separation (GS) and pervaporation (PV) mainly based on solution-diffusion mechanism, are two important processes for the challenging transport and separation of gaseous and vapor molecules. Various types of contemporary nanomaterials such as covalent organic frameworks (COFs) and metal organic frameworks (MOFs) have demonstrated unique channels with tuneable surface that govern transport and separation of targeted molecules. New opportunities have been revealed through incorporation of emerging nanomaterials into the structure of conventional polymeric membranes and resulted in several advantages notably improved performance and reduced energy consumptions. Due to the broad applications of GS and PV processes in the chemical industry and energy sector, the present manuscript aims to review the principle for gas separation and pervaporation in membrane molecular separation process in terms of solution-diffusion theory. In addition, the current status of membranes containing emerging nanomaterials for GS and PV are discussed comprehensively from different aspects. Furthermore, the current applications of nanomaterials incorporated mixed matrix membranes (MMMs) are described. Finally, the perspectives and future directions of remarkable performance membranes incorporated with diverse emerging nanomaterials are explained so as to facilitate the rapid advancement of energetic-efficient membranes toward practically industrial applications.

A commercial polydimethylsiloxane (PDMS) membrane was employed to separate the soluble toluene compounds (C7H8) from an aqueous solution via the pervaporation (PV) process. The performance and the efficacy of the PDMS PV membrane were evaluated through the estimation of the permeation flux and separation factor under various operating parameters. The response surface method (RSM) built in the Minitab-18 software was used for the design of the experiment in this study, and the responses of the permeation flux and the separation factor were analyzed and optimized based on the operating conditions. A nonlinear regression analysis was applied to the experimental output and input, and as a result, a quadratic equation model with parameters interactions was obtained as mathematical expressions to predict the permeation flux and separation factor. At the optimal conditions of temperature 30 °C, initial toluene concentration 500 ppm, and feed flowrate 3.5 L/min, the toluene permeation flux and separation factor were 125.855 g/m2·h and 1080, respectively. The feed concentration was the most impactful and significant in the improvement of the permeation flux and separation factor of the PDMS membrane.

This article discusses a molecular simulation of membrane processes for the separation of liquid mixtures during pervaporation. A method for simulating the structure of polyurethane membranes was developed. The method was based on the known mechanisms of the formation of macromolecules from constituent monomers. For the formation of a chemical bond between the monomers, values of the parameters of the potentials of intermolecular interactions were set so that bonds were formed only between the corresponding atoms. The algorithm was validated to produce polymer films from diphenylmethane diisocyanate (MDI) and amino ethers of boric acid (AEBA). The polymer film obtained according to the developed algorithm was used to study the adsorption of ethanol and water. The concentration distributions of the components inside the polymer film were obtained for films of various thicknesses. Modifications of the DCV-GCMD method were proposed for the molecular simulation of pervaporation. The algorithm was based on maintaining a constant density of the mixture in the control volume. After the molecules were added to the control volume, thermodynamic equilibrium was established. During this process, molecules moved only in the control volume, while the rest of the molecules were fixed. The proposed algorithm was used to calculate the flows of water and ethanol through the polymer film.

Poly(2,2′-biquinoline-6,6′-dicarbohydrazide)-co-(bistrimelliteimide)methylene-bisanthranylide (PHI) and its metal–polymer complex PHI-Cu(I) containing several types of functional groups (hydrazide, carboxyl, amide, and imide fragments) were synthesized to prepare two types of dense nonporous membranes. The study on morphology using scanning electron microscopy (SEM), measurements of mechanical, thermal, and transport properties of the membrane samples was carried out. The main mechanical properties of both membranes do not differ significantly, but the values of ultimate deformation differ palpably as a result of a non-uniform character of the deformation process for the PHI membrane. The thermal analysis based on the curves of thermogravimetric (TGA) and differential thermal (DTA) analyses of the PHI and PHI-Cu(I) membranes revealed peculiarities of the membrane structure. Transport properties were studied in pervaporation (PV) of methanol (MeOH) and dimethyl carbonate (DMC) mixtures including an azeotropic point. Intrinsic properties of the penetrant–membrane system were also determined. It was found that the total flux is higher through the PHI membrane, but the PHI-Cu(I) membrane exhibits a higher separation factor. Calculation of the pervaporation separation index (PSI) allowed to conclude that the PHI-Cu(I) membrane exhibits better transport properties as compared with the PHI membrane.

The pervaporation process is an energy-conservative and environmentally sustainable way for dehydration studies. It efficiently separates close boiling point and azeotrope mixtures unlike the distillation process. The separation of ethanol and water is challenging as ethanol and water form an azeotrope at 95.6 wt.% of ethanol. In the last few decades, various polymers have been used as candidates in membrane preparation for pervaporation (PV) application, which are currently used in the preparation of mixed matrix membranes (MMMs) for ethanol recovery and ethanol dehydration but have not been able to achieve an enhanced performance both in terms of flux and selectivity. Composite membranes comprising of poly (vinyl alcohol) (PVA) incorporated with carboxylated carbon nanotubes (CNT-COOH), graphene oxide (GO) and GO-CNT-COOH mixtures were fabricated for the dehydration of ethanol by pervaporation (PV). The membranes were characterized with Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Raman spectroscopy, Raman imaging, contact angle measurement, and water sorption to determine the effects of various nanocarbons on the intermolecular interactions, surface hydrophilicity, and degrees of swelling. The effects of feed water concentration and temperature on the dehydration performance were investigated. The incorporation of nanocarbons led to an increase in the permeation flux and separation factor. At a feed water concentration of 10 wt.%, a permeation flux of 0.87 kg/m2.h and a separation factor of 523 were achieved at 23 °C using a PVA-GO-CNT-COOH hybrid membrane.

In recent years, a well-known membrane-based process called pervaporation (PV), has attracted remarkable attention due to its advantages for selective separation of a wide variety of liquid mixtures. However, some restrictions of polymeric membranes have led to research studies on developing membranes for efficient separation in the PV process. Recent studies have focused on preparation of nanocomposite membranes as an effective method to improve both selectivity and permeability of polymeric membranes. The present study provides a review of PV nanocomposite membranes for various applications. In this review, recent developments in the field of nanocomposite membranes, including the fabrication methods, characterization, and PV performance, are summarized.

We address two major challenges facing commercialization of acetone-butanol-ethanol (ABE) fermentation: product inhibition and low productivity. We studied a polystyrene-b-polydimethylsiloxane-b-polystyrene (SDS) triblock copolymer membrane for selective removal of butanol from aqueous solutions by pervaporation. The SDS membrane exhibited higher permeabilities than a commercially available cross-linked polydimethylsiloxane (PDMS) membrane. Both types of pervaporation membrane were also used for in situ product removal of ABE biofuels in Clostridium acetobutylicum fermentations operated in a semi-continuous mode. Membrane performance and its effect on the fermentation process were assessed by measuring flux, OD600 and concentrations of different components in the fermenter as a function of time. Volumetric ABE productivity increased from 0.45g/(Lh) in simple batch fermentation to 0.66g/(Lh) in the case of pervaporative-fermentation with the PDMS membrane. A further increase in productivity to 0.94g/(Lh) was obtained in the case of pervaporative-fermentation with the SDS membrane. Overall, total ABE production improved by a factor of three, viable fermentation time increased by a factor of two, and cell density increased by a factor of 2.5 upon applying SDS membrane pervaporation, relative to the batch process.

We address two major challenges facing commercialization of acetone-butanol-ethanol (ABE) fermentation: product inhibition and low productivity. We studied a polystyrene-b-polydimethylsiloxane-b-polystyrene (SDS) triblock copolymer membrane for selective removal of butanol from aqueous solutions by pervaporation. The SDS membrane exhibited higher permeabilities than a commercially available cross-linked polydimethylsiloxane (PDMS) membrane. Both types of pervaporation membrane were also used for in situ product removal of ABE biofuels in Clostridium acetobutylicum fermentations operated in a semi-continuous mode. Membrane performance and its effect on the fermentation process were assessed by measuring flux, OD600 and concentrations of different components in the fermenter as a function of time. Volumetric ABE productivity increased from 0.45g/(Lh) in simple batch fermentation to 0.66g/(Lh) in the case of pervaporative-fermentation with the PDMS membrane. A further increase in productivity to 0.94g/(Lh) was obtained in the case of pervaporative-fermentation with the SDS membrane. Overall, total ABE production improved by a factor of three, viable fermentation time increased by a factor of two, and cell density increased by a factor of 2.5 upon applying SDS membrane pervaporation, relative to the batch process.

The structure, thermophysical characteristics, and pervaporation properties of composite membranes based on poly(vinyl alcohol) (PVA) are studied in dependence of the film preparation conditions. It is shown that the nature of the supramolecular organization of the composite polymer film determines which of the components of the separated mixtures of toluene and heptane predominantly penetrate through the corresponding pervaporation membrane. The observed structural effects can become more pronounced if the second component of a polymer mixture is purposefully selected (in this case, poly(N,N-dimethylaminoethyl methacrylate) instead of poly(acrylic acid)) or a nano-sized filler that can be well dispersed in the polymer matrix is introduced. Multi-wall carbon nanotubes are introduced into binary PVA-containing polymer blends. The influence of these fillers on the structure and transport properties of the obtained membranes is studied.

Gas permeation and pervaporation are technologies that emerged several decades ago. Even though they have discovered increasing popularity for industrial separation processes, they are not represented equally within process simulation tools except for commercial systems. The availability of such a numerical solution shall be extended due to the design of a membrane model with Visual Basic based on the solution-diffusion model. Although this works approach is presented for a specific process simulator application, the algorithm can generally be transferred to any other programming language and process simulation solver, which allows custom implementations or modeling. Furthermore, the modular design of the model enables its further development by operators through the integration of physical effects. A comparison with experimental data of gas permeation and pervaporation applications as well as other published simulation data delivers either good accordance with the results or negligible deviations of less than 1% from other data.

Metal–organic frameworks (MOFs), a sub-group of porous crystalline materials, have been receiving increasing attention for gas separation and pervaporation because of their high thermal and chemical stability, narrow window sizes, as well as tuneable structural, physical, and chemical properties. In this review, we comprehensively discuss developments in the formation of continuous MOF membranes for gas separation and pervaporation. Additionally, the application performance of continuous MOF membranes in gas separation and pervaporation are analysed. Lastly, some perspectives for the future application of continuous MOF membranes for gas separation and pervaporation are given.

The cornerstones of sustainable development require the treatment of wastes or contaminated streams allowing the separation and recycling of useful substances by a more rational use of energy sources. Separation technologies play a prominent role, especially when conducted by inherently environmentally friendly systems such as membrane operations. However, high-performance materials are more and more needed to improve the separative performance of polymeric materials nanocomposites are ideally suited to develop advanced membranes by combining organic polymers with suitable fillers having superior properties. In this area, polyether block amide copolymers (Pebax) are increasingly adopted as host matrices due to their distinctive properties in terms of being lightweight and easy to process, having good resistance to most chemicals, flexibility and high strength. In this light, the present review seeks to provide a comprehensive examination of the progress in the development of Pebax-based nanocomposite films for their application in several sensitive fields, that are challenging and at the same time attractive, including olefin/paraffin separation, pervaporation, water treatment, flexible films for electronics, electromagnetic shielding, antimicrobial surfaces, wound dressing and self-venting packaging. It covers a wide range of materials used as fillers and analyzes the properties of the derived nanocomposites and their performance. The general principles from the choice of the material to the approaches for the heterogeneous phase compatibilization as well as for the performance improvement were also surveyed. From a detailed analysis of the current studies, the most effective strategies to overcome some intrinsic limitations of these nanocomposites are highlighted, providing guidelines for the correlated research.

A developed polydimethylsiloxane (PDMS) membrane was used to separate soluble benzene compounds (C6H6) from an aqueous solution via a pervaporation (PV) process. This membrane was characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, contact angle (CA), and energy-dispersive spectroscopy (EDS). To evaluate the performance of the membrane, the separation factor and permeation flux were estimated in various operating conditions, including the feed temperature, initial benzene concentration, and feed flow rate. The experiments to maximize the separation factor and permeation flux were designed using the response surface method (RSM) that is built into Minitab 18. A quadratic model (nonlinear regression equation) was suggested to obtain mathematical expressions to predict the benzene permeation flux and the separation factor according to the effect of the parameters’ interaction. The optimization of the PV was performed using an RSM that was based on the analysis of variance (ANOVA). The optimal values of the benzene permeation flux and separation factor were 6.7 g/m2·h and 39.8, respectively, at the optimal conditions of temperature (30 °C), initial concentration of benzene (1000 ppm), and feed flow rate (3.5 L/min). It was found that the feed concentration was the most influential parameter, leading to a significant increase in the permeation flux and separation factor of the PDMS membrane.

This is part 2 of the research on pervaporation membranes for seawater desalination based on Geo–rGO–TiO2 nanocomposite. The quality of the Geo–rGO–TiO2 pervaporation membranes (PV), as well as the suitability of the built pervaporation system, is thoroughly discussed. The four membranes described in detail in the first article were tested for their capabilities using the parameters turbidity, salinity, total suspended solids (TSS), and electrical conductivity (EC). The membranes’ flux permeate was measured as a function of temperature, and salt rejection was calculated using the electrical conductivity values of the feed and permeate. Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) techniques were used to investigate changes in the chemical composition and internal structure of the membranes after use in pervaporation systems. The morphology of the membrane’s surfaces was examined by means of scanning electron microscopy (SEM), and the elemental distribution was observed by using X-ray mapping and energy dispersive spectroscopy (EDS). The results showed that the pervaporation membrane of Geo–rGO–TiO2 (1, 3) achieved a permeate flux as high as 2.29 kg/m2·h with a salt rejection of around 91%. The results of the FTIR and XRD measurements did not show any changes in the functional group and chemical compositions of the membrane after the pervaporation process took place. Long-term pressure and temperature feed cause significant cracking in geopolymer and Geo–TiO2 (3) membranes. SEM results revealed that the surface of all membranes is leached out, and elemental distribution based on X-ray mapping and EDS observations revealed the addition of Na+ ions on the membrane surface. The study’s findings pave the way for more research and development of geopolymers as the basic material for inorganic membranes, particularly with the addition of rGO–TiO2 nanocomposites.

Metal-organic frameworks (MOFs) are perceptive modifiers for the creation of mixed matrix membranes to improve the pervaporation performance of polymeric membranes. In this study, novel membranes based on polyvinyl alcohol (PVA) modified with Zr-MOFs (MIL-140A, MIL-140A-AcOH, and MIL-140A-AcOH-EDTA) particles were developed for enhanced pervaporation dehydration of isopropanol. Two membrane types (substrateless–freestanding; and formed on polyacrylonitrile support-composite) were prepared. The additional cross-linking of membranes with glutaraldehyde was carried out to circumvent membrane stability in pervaporation dehydration of diluted solutions. The synthesized Zr-MOFs were characterized by scanning electron microscopy, X-ray powder diffraction analysis, and specific surface area measurement. The structure and physicochemical properties of the developed membranes were investigated by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, thermogravimetric analysis, swelling experiments, and contact angle measurements. The PVA and PVA/Zr-MOFs membranes were evaluated in pervaporation dehydration of isopropanol in a wide concentration range. It was found that the composite cross-linked PVA membrane with 10 wt% MIL-140A had optimal pervaporation performance in the isopropanol dehydration (12–100 wt% water) at 22 °C: 0.15–1.33 kg/(m2h) permeation flux, 99.9 wt% water in the permeate, and is promising for the use in the industrial dehydration of alcohols.

Acetic acid was separated from a dilute mixture using a commercial polyvinyl alcohol (PVA) membrane. Intrinsic separation characteristics of the membrane were studied as a function of temperature. The degree of membrane swelling decreased marginally with increase in feed temperature. At 25oC the maximum degree of swelling was found out to be 46.3%, which reduced to 39.5% at 65oC. Although the pervaporation flux increased with increasing temperature of the liquid feed mixture, the separation factor decreased. From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters for water permeation were estimated. Diffusion and partition coefficient for water and acid were found to increase with temperature, but the diffusion coefficient of water was substantially higher than that of acetic acid at a constant feed concentration. The membrane used in the present study could tolerate highly concentrated corrosive acetic acid, thus may be useful for dehydration of other organics.

Purification and concentration of bioalcohols is gaining new status due to their use as a promising alternative liquid biofuel. In this work, novel high-performance asymmetric membranes based on a block copolymer (BCP) synthesized from polydimethylsiloxane (PDMS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) were developed for enhanced pervaporation dehydration of ethanol. Improvement in dehydration performance was achieved by obtaining BCP membranes with a “non-perforated” porous structure and through surface and bulk modifications with graphene oxide (GO). Formation of the BCP was confirmed by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. The changes to morphology and physicochemical properties of the developed BCP and BCP/GO membranes were studied by scanning electron (SEM) and atomic force (AFM) microscopies, thermogravimetric analysis (TGA) and contact angle measurements. Transport properties of the developed membranes were evaluated by the pervaporation dehydration of ethanol over a wide concentration range (4.4–70 wt.% water) at 22 °C. The BCP (PDMS:PPO:2,4-diisocyanatotoluene = 41:58:1 wt.% composition) membrane modified with 0.7 wt.% GO demonstrated optimal transport characteristics: 80–90 g/(m2h) permeation flux with high selectivity (76.8–98.8 wt.% water in the permeate, separation factor of 72–34) and pervaporation separation index (PSI) of 5.5–2.9.

In this work, silica nanoparticles were produced in situ, to be embedded eventually in the polyamide layer formed during interfacial polymerization for fabricating thin-film nanocomposite membranes with enhanced performance for dehydrating isopropanol solution. The nanoparticles were synthesized through a sol-gel reaction between 3-aminopropyltrimethoxysilane (APTMOS) and 1,3-cyclohexanediamine (CHDA). Two monomers—CHDA (with APTMOS) and trimesoyl chloride—were reacted on a hydrolyzed polyacrylonitrile (hPAN) support. To obtain optimum fabricating conditions, the ratio of APTMOS to CHDA and reaction time were varied. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to illustrate the change in morphology as a result of embedding silica nanoparticles. The optimal conditions for preparing the nanocomposite membrane turned out to be 0.15 (g/g) APTMOS/CHDA and 60 min mixing of APTMOS and CHDA, leading to the following membrane performance: flux = 1071 ± 79 g∙m−2∙h−1, water concentration in permeate = 97.34 ± 0.61%, and separation factor = 85.39. A stable performance was shown by the membrane under different operating conditions, where the water concentration in permeate was more than 90 wt%. Therefore, the embedment of silica nanoparticles generated in situ enhanced the separation efficiency of the membrane.

Ester have important applications in medicine chemical industry, but esterification is a typical reversible reaction controlled by thermodynamic equilibrium. In the study, a new type of catalytic composite membrane (CCM) with SA-MoS2/PAN as separation layer was reported. By-product water was proposed by pervaporation membrane reactor to improve the conversion rate of acetic acid. In 10 wt% ethanol-water solution, the separation factor of the catalytic composite membrane is 145 and the flux is 547 g m−2 h−1. Under the optimal condition, the acetic acid conversion rate reached 94.3%, which was 29% higher than that of batch reaction. The effects of single-layer catalytic membrane and double-layer catalytic membrane on acetic acid conversion rate were studied, which showed that the double-layer catalytic membrane had higher stability in esterification reaction.It is proved that high crosslinking degree can improve the stability of the membrane and reduce the conversion rate of acetic acid.

Thin film composite (TFC) membrane, composed of an ultrathin selective layer and a microporous support layer, has exhibited its great potential for pervaporation applications, because of the high permeability, facile fabrication, and individual optimization of the support and selective layers. In this review paper, we summarize the research progress of TFC membranes in pervaporation applications detailly. Herein, pervaporation fundamentals are briefed, including performance parameters and transport mechanisms involved in liquid-liquid separation and pervaporation desalination. The fabrication methods of support and selective layers, i.e., non-solvent induced phase inversion and electrospunning for the former, as well as interfacial polymerization and layer by layer assembly for the latter are elaborated respectively. Furthermore, the optimization strategies of support and selective layers are also summarized, including material section, filler incorporation, membrane-forming condition, co-solvent assistance, and surface modification. Subsequently, the performance status of TFC membranes is analyzed for various applications, including organic dehydration, organic recovery, and desalination. Finally, the challenges and future perspectives are also presented. We hope that this review can give researchers some guidance for the design and further development of TFC membrane in pervaporation processes.

Organophilic pervaporation (PV) mixed matrix membranes (MMMs) possess huge potential in organic wastewater treatment with merits of environmentally friendly and high-efficiency. The filler dispersion structure inside MMMs is required to explore in depth to upgrade the PV performance. In this study, an ethoxysilyl functionalized ionic liquid (IL-PTES) modified ZIF-8 nanoparticles (IL-PTES@ZIF-8) were synthesized by one-pot method, and then incorporated into the PDMS matrix to prepare MMMs for PV separation of ethyl acetate (EtOAc) from its diluted aqueous solution. The preferential adsorption performances to EtOAc by IL-PTES, especially for the functions of specific chemical groups in IL-PTES, were researched via molecular dynamicssimulation approach. Furthermore, the IL-PTES covered on ZIF-8 surface could crosslink with PDMS chains, thereby enhancing the interfacial compatibility between ZIF-8 and PDMS. Importantly, the self-aggregated IL-PTES subtly “glued” the nanoparticles together to lead IL-PTES@ZIF-8 a relatively continuous and defect-free distribution state. This condition would lead to a high-efficiency molecular pathway with less polymer phase and much relatively continuous ZIF-8 phase with high selectivity. PV results suggested that the MMMs with 15% IL-PTES@ZIF-8 loading displayed an optimal separation performance with an ultra-high separation factor of 492 (158.7% more than that of pristine PDMS membrane) and normalized EtOAc flux of 4.98 ​kg ​μm ​m−2·h−1 (2 times as much as that of pristine PDMS membrane) for separating 1 ​wt% EtOAc aqueous solution at 30 ​°C. These findings offered significant advancement toward developing high-performance MMMs enabled by the synergy of MOFs and ionic liquid.

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.

Membrane dialysis is studied as a promising technique for partial dealcoholization of white wines. The performance of three membrane processes applied for the partial dealcoholization of white wines of the Verdejo variety has been studied in the present work. Combination of Nanofiltration with Pervaporation, single step Pervaporation and, finally, Dialysis, have been applied to white wines from same variety and different vintages. The resulting wines have been chemically and sensorially analyzed and results have been compared with initial characteristics of the wines. From the results obtained, we can conclude that all procedures lead to significant alcohol content reduction (2%, 0.9% and 1.23% v/v respectively). Nevertheless, the best procedure consists in the application of Dialysis to the wines which resulted in a reasonable alcohol content reduction while maintaining organoleptic properties (only 14 consumers were able to distinguish the filtered and original wines, with 17 consumers needed to be this differences significant) and consumer acceptability of the original wine. Therefore, membrane dialysis, as a method of partial dealcoholization of white wines, has undoubted advantages over other techniques based on membranes, which must be confirmed in subsequent studies under more industrial conditions. This work represents the first application of Dialysis for the reduction of alcohol content in wines.

As a kind of volatile organic compound (VOC), methyl tert-butyl ether (MTBE) is hazardous to human health and destructive to the environment if not handled properly. MTBE should be removed before the release of wastewater. The present work supported the methyl-modified silica layer (MSL) on porous α-Al2O3 ceramic membranes with methyltrimethoxysilane (MTMS) as a precursor and pre-synthesized mesoporous silica microspheres as dopants by the sol-gel reaction and dip-coating method. MTMS is an environmentally friendly agent compared to fluorinated alkylsilane. The MSL-supported Al2O3 ceramic membranes were used for MTBE/water separation by pervaporation. The NMR spectra revealed that MTMS evolves gradually from an oligomer to a highly cross-linked methyl-modified silica species. Methyl-modified silica species and pre-synthesized mesoporous silica microspheres combine into hydrophobic mesoporous MSL. MSL makes the α-Al2O3 ceramic membranes transfer from amphiphilic to hydrophobic and oleophilic. The MSL-supported α-Al2O3 ceramic membranes (MSL-10) exhibit an MTBE/water separation factor of 27.1 and a total flux of 0.448 kg m−2 h−1, which are considerably higher than those of previously reported membranes that are modified by other alkylsilanes via the post-grafting method. The mesopores within the MSL provide a pathway for the transport of MTBE molecules across the membranes. The presence of methyl groups on the external and inner surface is responsible for the favorable separation performance and the outstanding long-term stability of the MSL-supported porous α-Al2O3 ceramic membranes.

The removal of volatile organic compounds (VOCs) from wastewater containing nonvolatile salts has become an important and interesting case of the application of the pervaporation (PV) process. The aim of this study was to evaluate the influence of salts on the PV removal of ethyl acetate from wastewater using a polydimethylsiloxane (PDMS) membrane. The fouled membrane was then characterized via scanning electron microscopy–energy-dispersive X-ray analysis (SEM–EDX) to investigate salt permeation. The membrane backflushing process was carried out by periodically flushing the permeate side of the tubular membrane. The results demonstrated that salts (NaCl and CaCl2) could permeate through the PDMS membrane and were deposited on the permeate side. The presence of salts in the feed solution caused a slight increase in the membrane selectivity and a decrease in the permeate flux. The flux decreased with increasing salt concentration, and a notable effect occurred at higher feed-salt concentrations. A permeate flux of up to 98.3% of the original flux was recovered when the permeation time and backflushing duration were 30 and 5 min, respectively, indicating that the effect of salt deposition on flux reduction could be mitigated. Real, organic, saline wastewater was treated in a pilot plant, which further verified the feasibility of wastewater PV treatment.

Ethylene glycol (EG) is an essential reagent in the chemical industry including polyester and antifreeze manufacture. In view of the constantly expanding field of EG applications, the search for and implementation of novel economical and environmentally friendly technologies for the separation of organic and aqueous–organic solutions remain an issue. Pervaporation is currently known to significantly reduce the energy and resource consumption of a manufacturer when obtaining high-purity components using automatic, easily scalable, and compact equipment. This review provides an overview of the current research and advances in the pervaporation of EG-containing mixtures (water/EG and methanol/EG), as well as a detailed analysis of the relationship of pervaporation performance with the membrane structure and properties of membrane materials. It is discussed that a controlled change in the structure and transport properties of a membrane is possible using modification methods such as treatment with organic solvents, introduction of nonvolatile additives, polymer blending, crosslinking, and heat treatment. The use of various modifiers is also described, and a particularly positive effect of membrane modification on the separation selectivity is highlighted. Among various polymers, hydrophilic PVA-based membranes stand out for optimal transport properties that they offer for EG dehydrating. Fabricating of TFC membranes with a microporous support layer appears to be a viable approach to the development of productivity without selectivity loss. Special attention is given to the recovery of methanol from EG, including extensive studies of the separation performance of polymer membranes. Membranes based on a CS/PVP blend with inorganic modifiers are specifically promising for methanol removal. With regard to polymer wettability properties, it is worth mentioning that membranes based on hydrophobic polymers (e.g., SPEEK, PBI/PEI, PEC, PPO) are capable of exhibiting much higher selectivity due to diffusion limitations.

Polymer film membranes are used to solve specific separation problems that dictate structural requirements. Structural and morphological parameters of film membranes based on glassy polyheteroarylenes can be controlled in the process of preparation from solutions that opens up prospects for obtaining structured membranes required for targeted separation. In the case of aromatic poly(amide-imide)s, the possibility of controlling film formation and structure virtually has not been studied. In the present work, a series of homologous co-poly(amide-imide)s differing in the number of repeating units with carboxyl-substituted aromatic fragments was synthesized by polycondensation. Comparative analysis of the processes of formation of membranes with different morphologies based on these polymers under equal conditions was performed. New information was obtained about the influence of the amounts of carboxyl groups and the residual solvent on structural properties of asymmetric membranes. The influence of these factors on transport properties of dense membranes under pervaporation conditions was studied. It was demonstrated that in the case of carboxyl-containing poly(amide-imide)s, the domains formed during film preparation had a significant effect on membrane properties.

Esterification reactions show a limited conversion due to the presence of water, which favors the opposite reaction. The removal of water from the reaction mixture increases the production of the ester. Pervaporation is an effective dehydration technique, usually applied to binary mixtures. The effect on pervaporation of a reactive multicomponent system involving water, ethanol, ethyl lactate and lactic acid with high acid concentration (13.5 wt. %) at relatively low temperatures (40–80 °C) was studied. Three hydrophilic membranes mainly fabricated for dehydration purposes from Sulzer Chemtech were used, i.e., PERVAP™ 3100, PERVAP™ 2216 and PERVAP™ 1131. The last one revealed as the most suitable for the application and it was further characterized with binary and ternary solutions. The membrane showed high affinity for the lactic acid. The acid permeation played a key role in the water/ethanol and water/ethyl lactate selectivity. Lactic acid permeates and crystalizes in the permeate side of the membrane at very low water concentration (below 2 wt. %), causing a drop in flux and membrane selectivity. Ethyl lactate is responsible of the loss of integrity of the membranes.

This is the first of two papers about the synthesis and microstructure properties of the Geo–rGO–TiO2 ternary nanocomposite, which was designed to suit the criteria of a pervaporation membrane for seawater desalination. The performance and capability of Geo–rGO–TiO2 as a seawater desalination pervaporation membrane are described in the second paper. A geopolymer made from alkali-activated metakaolin was utilized as a binder for the rGO-TiO2 nanocomposite. A modified Hummer’s method was used to synthesize graphene oxide (GO), and a hydrothermal procedure on GO produced reduced graphene oxide (rGO). The adopted approach yielded high-quality GO and rGO, based on Raman spectra results. The nanolayered structure of GO and rGO is revealed by Transmission Electron Microscopy (TEM) images. The Geo–rGO–TiO2 ternary nanocomposite was created by dispersing rGO nanosheets and TiO2 nanoparticles into geopolymer paste and stirring it for several minutes. The mixture was then cured in a sealed mold at 70 °C for one hour. After being demolded, the materials were kept for 28 days before being characterized. Fourier Transform Infrared (FTIR) and X-ray Diffraction (XRD) measurements revealed that the geopolymer matrix efficiently bonded the rGO and TiO2, creating nanocomposites. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) was used to examine the morphology of the outer layer and cross-sections of nanocomposites, and the results displayed that rGO were stacked on the surface as well as in the bulk of the geopolymer and will potentially function as nanochannels with a width of around 0.36 nm, while TiO2 NPs covered the majority of the geopolymer matrix, assisting in anti-biofouling of the membranes. The pores structure of the Geo–rGO–TiO2 were classified as micro–meso pores using the Brunauer–Emmet–Teller (BET) method, indicating that they are appropriate for use as pervaporation membranes. The mechanical strength of the membranes was found to be adequate to withstand high water pressure during the pervaporation process. The addition of rGO and TiO2 NPs was found to improve the hyropobicity of the Geo–rGO–TiO2 nanocomposite, preventing excessive seawater penetration into the membrane during the pervaporation process. The results of this study elucidate that the Geo–rGO–TiO2 nanocomposite has a lot of potential for application as a pervaporation membrane for seawater desalination because all of the initial components are widely available and inexpensive.