Pervaporation Membranes Research Articles

The Role of Membranes in Modern Winemaking: From Clarification to Dealcoholization

The utilization of membrane technologies in winemaking has revolutionized various stages of production, offering precise and efficient alternatives to traditional methods. Membranes, characterized by their selective permeability, play a pivotal role in enhancing wine quality across multiple processes. In clarification, microfiltration and ultrafiltration membranes, such as ceramic or polymeric membranes (e.g., polyethersulfone or PVDF), effectively remove suspended solids and colloids, resulting in a clearer wine without the need for chemical agents. During stabilization, membranes such as nanofiltration and reverse osmosis membranes, often made from polyamide composite materials, enable the selective removal of proteins, polysaccharides, and microorganisms, thereby improving the wine’s stability and extending its shelf life. Additionally, in dealcoholization, membranes like reverse osmosis and pervaporation membranes, typically constructed from polydimethylsiloxane (PDMS) or other specialized polymers, facilitate the selective removal of ethanol while preserving the wine’s flavor and aroma profile, addressing the increasing consumer demand for low-alcohol and alcohol-free wines. This article provides a comprehensive analysis of the advancements and applications of membrane technologies in winemaking.

Effect of Side Substituent on Comb-like Polysiloxane Membrane Pervaporation Properties During Recovery of Alcohols C2-C4 from Water.

The pervaporation properties of membranes based on comb-like polysiloxanes when C2-C4 alcohols are removed from water were studied for the first time. It was established that membranes based on comb-like polysiloxanes with linear aliphatic and organosilicon substituents have increased permeability selectivity for C3+ alcohols. The obtained results were interpreted from the point of view of the solubility of the components of the separated mixture in polysiloxanes. It was shown that membranes based on polysiloxanes with linear substituents have increased butanol/water permeability selectivity (2.5-3.7). The achieved selectivity values correspond to the level of highly selective zeolite membranes, which allows for a reduction in energy consumption for the pervaporation removal of butanol by more than two times.

Enhanced biofuel dehydration using MXene-PES nanocomposite membranes via pervaporation

Efficient ethanol dehydration is vital for biofuel production, and pervaporation membranes are essential to this process. This study introduces a novel approach to synthesizing MXene nanoparticles, a two-dimensional material with exceptional properties, and incorporating them into polyether sulfone (PES) membranes. Characterization through XRD, FTIR, and RAMAN analyses confirmed the layered structure and chemical bonds of the MXene nanoparticles. The integration of MXene into PES membranes resulted in reduced contact angles, signifying enhanced hydrophilicity. Ethanol dehydration tests demonstrated that nanocomposite membranes with 0.5 wt.% MXene achieved 1.5 times higher permeation flux and 1.2 times higher selectivity compared to unmodified membranes. These performance enhancements are attributed to the improved hydrophilicity, uniform dispersion, and robust interaction of MXene within the polymer matrix. Furthermore, the study highlights that UV irradiation produces superior-quality membranes. This research underscores the potential of MXene-PES nanocomposite membranes to significantly improve the efficiency of biofuel dehydration processes.

Preparation of a swelling-resistant polyethyleneimine-based pervaporation membrane via surface gradient crosslinking for the separation of methanol/dimethyl carbonate

Preparation of a swelling-resistant polyethyleneimine-based pervaporation membrane via surface gradient crosslinking for the separation of methanol/dimethyl carbonate

Aromatic-aliphatic hydrocarbon separation with oriented monolayer polyhedral membrane.

Aromatic-aliphatic hydrocarbon separation is a challenging but important industrial process. Pervaporation membrane technology has the potential for separating these mixtures. We developed an oriented monolayer polyhedral (OMP) membrane that consists of a monolayer of ordered polyhedral particles and is anchored by hyperbranched polymers. It contains a high density of straight, selective nanochannels, enabling the preferential transport of aromatic molecules. Compared with traditional mixed-matrix membranes with random orientations, the OMP membrane improves the pervaporation separation index for aromatic-aliphatic hydrocarbon mixtures with C6 and C7 compounds, surpassing the performance of existing membranes by 3 to 10 times. This high performance demonstrates the potential of OMP membranes for hydrocarbon molecular separation and their application in the value-added separation of naphtha feedstocks.

Structural optimization of separation layer and porous PES substrate for enhanced pervaporation desalination performance

Pervaporation membranes with water-selective properties hold great potential for desalination and brine concentration applications. In this study, a modified PES porous membrane with smaller pore sizes and enhanced interfacial support was used as the substrate. Ultrathin selective layers were fabricated on its surface via atomized spray coating, resulting in high-performance pervaporation membranes for desalination analysis. The study compares the effects of PVA and PEI on membrane performance under different crosslinking systems. At 82 °C, using a 3.5 wt.% sodium chloride solution, the PES composite membrane with a PEI/SPTA selective layer achieved a maximum flux of 180.35 ± 13.8 kg m-² h⁻¹, with a salt rejection rate of 99.97% ± 0.2. Even at a higher brine concentration of 20 wt.%, the membrane maintained a flux of 49.77 ± 7.3 kg m-² h⁻¹ at 72 °C. The membrane's high salt rejection and stable performance under complex operating conditions demonstrate that pervaporation composite membranes prepared with low-surface-porosity substrates offer enhanced cycle stability and industrial potential in real-world desalination and concentration applications.

Development and Characterization of PVA Membranes Modified with In(BTC) Metal–Organic Framework for Sustainable Pervaporation Separation of Isopropanol/Water

In this study, pervaporation membranes from synthetic biodegradable polyvinyl alcohol (PVA) with improved properties for isopropanol dehydration were developed through modification with a synthesized In(BTC) metal–organic framework. The improvement in the PVA membrane properties was achieved by varying the In(BTC) concentration (2.5–7 wt.%) in the PVA matrix to allow us to select the optimal concentration for the membrane, which was further chemically cross-linked with maleic acid to increase the resistance, and developing a cross-linked supported membrane from the optimal PVA/5%In(BTC) composite for promising industrial applications. The synthesized In(BTC) and membranes were characterized by using spectroscopic, microscopic, X-ray diffraction, and thermogravimetric analysis methods, as well as swelling degree, contact angle measurements, and the Brunauer–Emmett–Teller adsorption model. The obtained regularities were confirmed by quantum chemical calculations. The cross-linked supported membrane from PVA/5%In(BTC) had optimal transport properties for isopropanol dehydration (20–90 wt.% water), 99.9–89.0 wt.% water in the permeate, and 0.142–0.341 kg/(m2h) of permeation flux, the rate of which was four times higher compared to the PVA membrane in separating 20–30 wt.% water/isopropanol.

Novel Mixed-Matrix Pervaporation Membrane Based on Polyether Block Amide Modified with Ho-Based Metal-Organic Framework.

Segmented polymers, such as polyether block amide (PEBA), exhibit unique properties due to the combination of different segments. PEBA consists of soft polyester and rigid polyamide blocks, enabling its use in various industrial applications, including membrane technologies. In this study, PEBA membranes modified with a holmium-based metal-organic framework (Ho-1,3,5-H3btc) were developed for enhanced pervaporation separation of water/isopropanol and water/phenol mixtures. The effect of 1-7 wt.% Ho-1,3,5-H3btc content variation and the selection of a porous substrate (commercial from fluoroplast F42L (MFFC) and developed membranes from polyvinylidene fluoride without (PVDF) and with a non-woven polyester support (PVDF-s)) on dense and/or supported membrane properties, respectively, was investigated. The dense and supported PEBA/Ho-1,3,5-H3btc membranes were studied by use of Fourier transform infrared spectroscopy, scanning electron and atomic force microscopies, swelling measurements, and pervaporation experiments. The supported membrane from PEBA with 5 wt.% Ho-1,3,5-H3btc applied onto the PVDF-s substrate exhibited optimal pervaporation performance: a 1040 g/(m2h) permeation flux and a 5.2 separation factor in water/phenol (1 wt.%) mixture separation at 50 °C due to optimal values of roughness, swelling degree, and selective layer thickness. This finding highlights the potential of incorporating Ho-1,3,5-H3btc into PEBA for developing high-performance pervaporation membranes.

Simultaneous enhancement of flux and selectivity of UiO-66 membranes for pervaporation via post-synthetic defect healing

Zirconium-based metal-organic framework (Zr-MOF) UiO-66 is widely recognized as an exceptional candidate for fabricating high-performance membranes owing to its rich porosity, customizable chemistry and remarkable stability. However, exploration of accessible zirconium sources for UiO-66 membrane fabrication is not enough and eliminating the undesired defects occurring during synthesis is also imperative. In this work, 1.3 μm thick UiO-66 polycrystalline membranes were successfully fabricated using ZrOCl2·8H2O as the sole metal source. The undesired lattice defects were controlled at a low concentration level through utilizing post-synthetic defect healing method, leading to simultaneous enhancement of flux and separation factor of UiO-66 membranes for pervaporation test as the competitive permeation between different penetrants was reduced to a large extent. The finally obtained UiO-66 membranes exhibited exceptional performance, with the separation factor of around 10,000 for alcohol/ether separation, showing good potential for applying in industrial production processes.

Fabrication of novel mixed-matrix membrane and its pervaporation process integration with distillation for energy-saving separation of DMC/methanol azeotropic mixture

Separation of azeotropic mixtures is a typical energy-intensive process in chemical industry, in which pervaporation membrane process shows great potential in energy efficiency. However, the performance of commercial membranes such as polydimethylsiloxane (PDMS) is unattractive for practical application. Henein, for the first time, we employed microporous MAF-6 as a new filler incorporating into PDMS membrane for pervaporation separation of DMC/methanol azeotropic mixture. The resulting MAF-6/PDMS mixed-matrix membrane with the optimal filler size of 300 nm and filler loading of 12 wt% exhibited highly DMC permeability (651–811.5 Barrer) and selectivity (10.1–10.4) during 31 days continuous separation process, which fairly exceeds the state-of-the-arts membrane performance. A pervaporation-distillation coupled process was further proposed for the purification of DMC/methanol mixtures, showing 55.7 % of energy-saving compared with conventional distillation process.

Flow channel simulation and optimization design of pervaporation membrane pool based on heat-mass-flow coupling

Pervaporation (PV), recognized as a separation technology with vast potential, is highly dependent on the fluid flow patterns within the membrane module, which play a critical role in local mass transfer processes on the membrane surface. In this study, computational fluid dynamics (CFD) was employed to simulate two different flow channel designs for a PV membrane module, with experimental verification of the model’s accuracy. The results indicated that the parallel inlet–outlet and wavy flow channel design (Mode II) significantly improved the feed-side concentration and temperature distribution, leading to a 3.7 % increase in feed-side flow velocity. Further investigation into the effects of three membrane pool structural parameters on separation performance revealed that pressure drop was most significantly influenced by the inlet radius, while the wavy length-to-height ratio (L:H) has the greatest impact on separation performance. After optimization, the optimal membrane module structure was determined to be the baffle depth of 4 mm, the inlet radius of 1 mm, and the L:H of 1:1. Based on this optimized structure, the effects of operating conditions on separation performance were further explored. The study showed that increasing feed flow rate significantly enhanced separation performance, while increasing feed temperature and concentration intensified temperature and concentration polarization on the membrane surface. Through multi-objective optimization, the optimal operating conditions were determined to be the feed flow rate of 20 L·h-1, feed temperature of 55 °C, and feed concentration of 3 wt%. This study provides valuable theoretical insights and technical references for the design of PV membrane pool flow channels and the selection of operational conditions.

In-situ formation of polyether membrane selective layer for pervaporation separation of azeotropic organic solvent mixtures

Pervaporation technology is suitable for separating organic solvent azeotropic mixtures or isomers that are challenging for traditional distillation methods. However, the conventional methods to fabricate pervaporation membranes often lead to limitations in membrane performance and stability, such as the restrictiveness of material selection and the high costs of manufacturing. Herein, we utilized commercially available inexpensive monomers CE (3,4-Epoxycyclohexylmethyl) and DOX (3-ethyl-3-[(3-ethyloxetan-3-yl)methoxymethyl]oxetane), along with the sulfonium salt photo-initiator (Ar6S2+SbF6-), to fabricate pervaporation membranes through cationic photopolymerization, resulting in separation layers enriched with ether groups. The resulting pervaporation membranes were employed to separate ethanol/n-hexane and ethanol/cyclohexane azeotropes formed during the production of ethyl acetate. The separation efficiency was significantly enhanced compared to the original PVDF membranes, achieving a separation factor of up to 162.81 for ethanol/n-hexane azeotrope and 41.89 for ethanol/cyclohexane azeotrope. During the 110-hour prolonged operation test, the membranes demonstrated exceptional tolerance and long-term stability against different organic solvents.

Design of Thermo-Responsive Pervaporation Membrane Based on Hyperbranched Polyglycerols and Elastin-like Protein Conjugates.

This paper reports the development of a highly crosslinked hyper-branched polyglycerol (HPG) polymer bound to elastin-like proteins (ELPs) to create a membrane that undergoes a distinct closed-to-open permeation transition at 32 °C. The crosslinked HPG forms a robust, mesoporous structure (150-300 nm pores), suitable for selective filtration. The membranes were characterized by FTIR, UV-visible spectroscopy, SEM, and AFM, revealing their structural and morphological properties. Incorporating a synthetic polypeptide introduced thermo-responsive behavior, with the membrane transitioning from impermeable to permeable above the lower critical solution temperature (LCST) of 32 °C. Permeation studies using crystal violet (CV) demonstrated selective transport, where CV permeated only above 32 °C, while water permeated at all temperatures. This hybrid HPG-ELP membrane system, acting as a molecular switch, offers potential for applications in drug delivery, bioseparations, and smart filtration systems, where permeability can be controlled by temperature.

Self-assembled ILs-PVA micelle nanostructure impart the pervaporation membrane with high ethanol dehydration performance

Achieving strong interaction with the targeted composition and constructing abundant transport channels is crucial to obtain the pervaporation (PV) membrane with high selectivity and flux. Here, three ionic liquids (ILs) were screened out based on their relative selectivity and capacity targeting for bioethanol dehydration by COSMO-RS. The interaction energies analysis between ILs, EtOH, and H2O suggests that the ILs can form strong hydrogen bonds with water and disrupt the hydrogen bond in the EtOH–H2O azeotropic mixture, which is beneficial for improving the selectivity. Furthermore, driven by the multiple hydrogen bonds, electrostatic interactions, and van der Waals forces, ILs could self-assemble with polyvinyl alcohol (PVA) to fabricate the PV membrane with well-ordered micelle nanostructure, as its structure was revealed by MD simulations. The formation of the ILs-PVA micelle dramatically influenced membrane surface morphology, roughness, and water contact angle, providing an extra transport channel for the membrane. The optimal membrane (at the cmc point) exhibited a superior ethanol dehydration separation factor of 1627, along with a flux of 684 g/m2h at 50 °C. It can be expected that this novel self-assembled ILs-PVA micelle nanostructure strategy will find promising applications in other azeotropic mixture separation processes, like ethanol-ethyl acetate, water-butanol, etc.

Enhancing permeability of CA/MoS2 pervaporation membrane via electric field-induced orientation of MoS2 nanosheets

The formation of a mixed matrix membrane by incorporating nanofillers into a polymer matrix is a potential strategy to improve the separation performance of polymer membranes. However, agglomeration and random arrangement of nanofillers in the mixed matrix membrane result in lower permeation flux increase than expected. In this work, mixed matrix membranes composed of cellulose acetate polymer and varying amounts of Molybdenum disulfide (MoS2) nanosheets as nanofillers were prepared, and an electric field was applied to induce the alignment of MoS2 nanosheets in the membrane thickness direction. The effects of solution parameters including solvent type, MoS2 content, and polymer concentration as well as electric field parameters i.e., frequency, strength, and action time on MoS2 orientation were investigated using a stereoscopic microscope. The pervaporation desalination performance of mixed matrix membranes with randomly arranged MoS2 and orientally arranged MoS2 was assessed. At 2 wt% MoS2 content, the mixed matrix membrane with orientally arranged MoS2 exhibited a flux of 5.44 kg/(m2·h), representing a 25.9 % increase over the mixed matrix membrane with randomly arranged MoS2, while maintaining a salt rejection rate of over 99.9 %. The mixed matrix membrane demonstrated good long-term stability with consistent water flux and salt rejection during 120 h of operation.

Preparation of PDMS permeation membrane by emulsion dilution method and its separation performance for aromatics

Natural aroma compounds are a kind of important food additive. Taking bis(2-ethylhexyl) sodium sulfosuccinate (AOT) as the surfactant, water-in-n-heptane emulsions were prepared. Then, the emulsions were adopted as the diluter to prepare polydimethylsiloxane (PDMS) pervaporation membranes using the emulsion templating method (ePDMS), of which the separation layer was controlled by the template action of emulsion drops. The ePDMS membranes were utilized to separate aroma compounds. Field-emission scanning electron microscope (FESEM) analysis revealed that the surface of the ePDMS membrane remained smooth, and white light interferometry confirmed the membrane’s surface smoothness. FESEM cross-sectional analysis exposed the voids left by the evaporation of the emulsion, rendering the separation layer of the ePDMS membrane more porous. Water contact angle measurements demonstrated the hydrophobicity of the ePDMS membrane, which is advantageous for the pervaporation of aromatic compounds. Fourier transform infrared spectrometry analysis confirmed the evaporation and separation of the emulsion, retaining the original chemical properties of the PDMS membrane. In an ethanol–water system, the permeation flux of ethanol in ePDMS membranes prepared with 1 emulsion (Vwater:Vn-heptane = 1:9; mass concentration of AOT of 1.0 mg/ml) is 90.6% higher than that in PDMS membranes, while the separation factor does not change obviously. The separation performance of ePDMS membranes for linalool in water was further studied. Results show that the permeation flux and separation factor of linalool in ePDMS composite membranes at 50 °C are 786 g m−2 h−1 and 17.69, which separately increase by 84.7% and 27.1% compared with those in PDMS membranes. This indicates that adding ethanol exerts a significant synergistic effect on the separation of linalool.

Graphene Oxide and its Composites: Advanced Membranes for Selective Water Permeation.

Graphene oxide (GO) membranes have gained significant attention as a promising material for separation by selective permeation processes due to their advantageous structural and chemical properties, including high water permeability, chemical resistance, and mechanical strength. In this study, we explore the potential applications of GO membranes in pervaporation to separate liquid mixtures. The layered structure and hydrophilic nature of GO membrane facilitate rapid and selective water transport through angstrom-scale interlayer spacings, resulting in superior performance over conventional polymeric and inorganic membranes. The unique mass transport mechanisms - slip flow and molecular alignment - enable GO membranes to selectively permeate water over organic solvents. For chemical dehydration, GO membranes are the most potential candidates. Furthermore, advancements in composite GO membranes and cross-linking techniques that improve their stability and separation performance are discussed. This study highlights the advantages of GO membranes and their potential to replace or complement existing technologies, by emphasizing their role in advancing membrane-based separation and promoting environmental sustainability. Future research is expected to optimize the fabrication techniques for GO membranes and expand their application scope.

A novel TFNi pervaporation membrane with g-C3N4 quantum dots for high-efficiency IPA dehydration

Pervaporation (PV) shows significant potential for the highly selective isopropanol (IPA). The pursuit of developing PV membranes with outstanding separation effect and enduring high purity permeation is an indispensable goal. Based on polyamide (PA) separation layers, a polydopamine (PDA) mixed g-C3N4 quantum dots (gCNQDs) coating as the interlayer was deposited onto a porous ceramic hollow fiber substrate to fabricate thin-film nanocomposite membranes with an interlayer (TFNi). The nanocomposite interlayer enabled the formation of a smoother and highly separated selective polyamide layer. The separation factor exhibited a 31-fold enhancement with the augmentation of the blending fraction of gCNQDs during the PDA coating process. The resulting TFNi membrane attained an exceedingly high separation factor of 10270 ± 90 with a permeate water concentration of 99.9 % and demonstrated a satisfactory flux of 1.40 ± 0.08 kg m−2 h−1 during the PV process of 90 wt% IPA dehydration at 60 °C. This study presents a fresh perspective on the implementation of nanocomposite interlayers, which is expected to expand the application of high-performance TFNi membranes in PV dehydration processes.

Experimental and theoretical insights into bioethanol recovery: Valorizing waste PET bottles for sustainable pervaporation membranes

The use of bioethanol as an alternative source of fuel could solve energy and pollution concerns. However, its conventional recovery procedures make the overall process costly and energy intensive. Membrane-based pervaporation (PV) has gained significant attention in recent years. Most membranes that purify bioethanol are fabricated from conventional fossil-based polymers. This study presents the first work for biofuel separation by valorizing waste polyethylene terephthalate (PET) bottles into PV membranes. The performance of the membrane was characterized in terms of FTIR, XRD, TGA, WCA, SEM, and AFM and tested for a 10 wt% ethanol–water feed mixture at different temperatures. The mild hydrophobic character of PET allowed the PV membrane to achieve a separation factor of 10.45, a total flux of 1.7 kg m−2h−1, and a pervaporation separation index (PSI) of 18.72 at 45 °C. The recycled PET membrane (rPET) has higher mass transfer resistance for water compared to ethanol. The density functional theory (DFT) analysis confirms a stronger affinity of PET membrane towards ethanol than water. The results showed that rPET membranes have competitive performance compared to conventional fossil-based derived membranes. This study explores an energy-environment nexus approach, which could significantly contribute to achieving the key United Nations’ sustainable development goals.

The Efficiency of Polyester-Polysulfone Membranes, Coated with Crosslinked PVA Layers, in the Water Desalination by Pervaporation.

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.