High Pervaporation Performance Research Articles

Fabrication of high-performance pervaporation desalination composite membranes with study of its acid-base stability

In the process of industrial production will produce a lot of acid and alkaline waste liquid, how to effectively treat acid and alkali waste liquid is an important topic at present. At present, there are some problems about the treatment of acid and alkali waste liquid, such as large investment, complicated process and low efficiency. Pervaporation has the characteristics of mild operating conditions and no influence of osmotic pressure threshold, so it has great application potential in the concentration, reuse and reduction of acid and alkali waste liquid. However, at present, conventional pervaporation dense membrane materials cannot maintain long-term stability in strong acid and alkali environment, in order to achieve this performance, we use perfluorosulfonic acid resin with good acid and alkali resistance as the dense layer substrate. PFSA/PTFE/PP composite membrane was prepared by spraying process, and the final prepared composite membrane had a pure water flux of 45 ± 1.2 kg/(m2∙h) at 70 ℃. The acid and alkali resistance of the intrinsic membrane and the composite membrane was evaluated, and it was found that the feed liquid was concentrated to 20 wt% after 19 h long concentration operation at 70℃ and starting liquid was 5 wt% H2SO4 and 5 wt% NaOH. The retention rate of acid and alkali can be maintained above 99.9 %. During the concentration of H2SO4 solution, the dense layer structure is affected, and the pure water flux of the composite membrane is reduced, eventually maintaining around 32 kg/(m2∙h). In the process of concentrating NaOH solution, the pure water flux of the composite membrane increased first and then decreased, and the final pure water flux of the membrane remained near 40 kg/(m2∙h).

High-performance double-separation-layer pervaporation membranes for ethanol dehydration

Pervaporation membranes are used to dehydrate ethanol, but standalone sodium alginate (SA) and polyvinyl alcohol (PVA) membranes pose challenges owing to their inherent issues, such as low stability and limited separation performance. Despite employing various complex and costly membrane preparation methods to address these shortcomings, the improvement in separation performance, especially in permeate flux, remains limited. In addition, the complexity and costliness of these methods hinder their industrial applications. Herein, we developed a simple and cost-effective method to prepare high-performance pervaporation membranes. First, a SA solution was cast on the polyacrylonitrile (PAN) bottom membrane to form a SA separation layer, and subsequently a PVA separation layer was applied atop of the SA separation layer, yielding double-separation-layer PVA/SA/PAN membranes. The smooth, compact and hydrophilic SA intermediate layer apparently decreased the defects in the PVA separation layer and the presence of the PVA separation layer isolated the SA layer from the liquid feed on the outer side and inhibited the swelling of SA separation layer, leading to high selectivities and stabilities. Under operating conditions of 69°C and a feed ethanol concentration of 90 wt%, the permeate flux and separation factor of the PVA4/SA/PAN membrane are 1201 g m−2 h−1 and 5164, respectively. Notably, the pervaporation separation index (PSI) of this membrane is 79 times that of the PVA4/PAN membrane. Moreover, the membrane performance remained stable over a continuous 10-day operation at 69°C, affirming its reliability and durability. We successfully prepared a high-performance two-separation-layer pervaporation membrane for ethanol dehydration.

Combining dip-coating and rotate-drying to preparation of PDMS on SiC tubular support with macropore for high pervaporation performance

High-performance polydimethylsiloxane (PDMS)/ceramic tubular pervaporation membranes have potential in industrial separation applications, but realizing the preparation of PDMS layer on the ceramic supports with micrometer-scale pore size (0.8 μm or 4.3 μm) for improving performance remains a challenge. We report a strategy (combined dip-coating and rotate-drying, DCRD) to preparation of PDMS on silicon carbide (SiC) tubular support with macropore. Response surface methodology was employed to optimize the dip-coating process, and the influence of friction velocity on tubular composite membranes was investigated. The results indicate that pulling speed, casting solution viscosity, and their interaction have significant effects on the pervaporation performance of PDMS/SiC tubular composite membranes. Moreover, increasing friction velocity results in uneven PDMS layer thickness, which in turn impacts the pervaporation performance of the composite membrane. Furthermore, the rigid structure of SiC restricts the movement of PDMS polymer chains, enabling the composite membrane to maintain stable pervaporation performance at higher isobutanol feed concentrations (3 wt%) or elevated feed temperatures (60 °C). After continuous operation for 200 h, the developed PDMS/SiC tubular composite membrane consistently maintained the total flux of 650 g m−2 h−1 and the separation factor of 39 for isobutanol/water. Eventually, this novel fabrication method offers new insights into the preparation of various other organic-inorganic tubular composite membranes.

Construction of graphene oxide intercalated with UiO-66-PEI heterostructure membrane for efficient pervaporation dehydration of isopropanol

The separation of isopropanol (IPA)-water mixtures is a critical process in chemical, bioprocess, and electronics industries. This study aims to develop a high-performance pervaporation (PV) membrane for IPA-water separation through incorporating UiO-66-PEI into graphene oxide (GO) membrane by leveraging the combined properties of 2D and 3D nanomaterials. Polyethyleneimine (PEI) was grafted into UiO-66-NH2 to synthesize UiO-66-PEI using Schiff base reactions with glutaraldehyde. The UiO-66-PEI was subsequently intercalated into GO layers to fabricate the membrane in hydrolyzed polyacrylonitrile support using pressure filtration. This intercalation significantly impacted the chemical properties and structure of the GO, leading to an enhanced PV performance in IPA-water mixture separation. The resulting membrane demonstrated a remarkable separation efficiency with a permeation flux of 1479 g∙m−2∙h−1 and a high water content in the permeate of 99.60 wt%. Notably, the exceptional separation performance of the nanocomposite membranes was sustained across varying feed concentrations, operating temperatures, and during long-term operational periods. The findings in this work offer valuable insights into the fabrication of GO-based heterostructure membranes with significant implications for advancing PV separation technology.

Composite membranes from bio-inspired catechol-amine coatings for pervaporation desalination

Compared with reverse osmosis, pervaporation is less influenced by the osmosis pressure of the feed solution, which endows it as an attractive desalination technology. Many researches focus on developing high-performance pervaporation desalination membranes. Bio-inspired polyphenol coatings are versatile tools for engineering membrane surfaces. Here, catechol-amine chemistry was the first time applied to construct dense composite pervaporation desalination membranes via a stepwise coating method. Tannic acid (TA) and polyethyleneimine (PEI) were chosen as typical materials. Fabrication parameters, including TA and PEI concentrations in the coating solution, pH, and thermal annealing, are crucial to the desalination performance of the resulting membranes. The TA-PEI interactions were studied by the UV–Vis absorption spectroscopy method. The membrane prepared at optimal conditions exhibits excellent desalination performance. The water flux was 43 kg/(m2·h) at 50 °C for the feed of 3.5 wt% NaCl solution (95 kg/(m2·h) at 70 °C). The intrinsic hydrophilicity of the selective layer material ensures the membrane processes of good antifouling performance. This work demonstrates the possibility and potential of applying bio-inspired catechol-amine chemistry to prepare pervaporation desalination membranes.

Tailoring fully crosslinked polyamide layers on optimized polyacrylonitrile supports via coactive delayed phase inversion and alkaline hydrolysis for brine treatment through pervaporation

A novel method of co-hydrolysis of polyacrylonitrile (PAN) support to host polyamide (PA) formation using coactive delayed phase inversion is presented to synthesize high-performance pervaporation membranes. Pure water in the coagulation bath was replaced with a 1.0 M sodium hydroxide solution maintained at 50 °C, allowing concurrent hydrolysis and delayed phase inversion. The characterization results revealed a smoother surface morphology, a higher carboxylic group content, improved hydrophilicity, and an ideal O/N ratio (∼1) of the PA layer on the co-hydrolyzed PAN (HPAN-Co) support compared with the PA layer on the post-hydrolyzed PAN (HPAN-Post) support. Furthermore, the typical pattern observed in PA-HPAN-Post, with a plethora of finger-like pores followed by macrovoids, completely disappeared and was replaced by a uniform and fine microvoid structure in PA-HPAN-Co, with an approximately 50 % reduction in membrane thickness. This led to a reduction in membrane swelling and salt transport without compromising the permeation flux. The pervaporation tests with a 10 wt% NaCl feed at 70 °C using PA-HPAN-Co showed a 99.97 % salt rejection ability and a 74.2 kg m−2h−1 flux, which is 33 % higher than the permeate flux of PA-HPAN-Post. Thus, the PA-HPAN-Co membrane is highly recommended for pervaporative desalination, considering the enhanced performance and scalability of the synthesis technique.

High performance MOF UiO-66 membranes for MeOH/MTBE separation

The preparation of high-performance polycrystalline MOF membranes for MeOH/MTBE separation poses a challenge. In this study, intact 400 nm thick UiO-66 membranes with well-controlled structures were successfully fabricated using a novel formulation. The high ligand/metal ratios and the new zirconium sources provide ideas for designing UiO-66 membranes with effective pore structures. Consequently, the membranes exhibited an exceptional pervaporation performance, achieving a flux of 5.68 kg m−2 h−1 and a separation factor of 28000 for MeOH/MTBE (5/95 wt/wt.%) at 40 °C. Further, the UiO-66 membranes have excellent temperature and concentration resistance and remain stable during 120 h of operation. The high pervaporation performance, along with this stability, demonstrates that this UiO-66 membrane is a competitive candidate for MeOH/MTBE separation.

Thin selective layered mixed matrix membranes (MMMs) with defective UiO-66 induced interface engineering toward highly enhanced pervaporation performance

The thin selective layer in mixed matrix membranes (MMMs) with high pervaporation performance is in high demand because of their high productivity. However, it has been limited because of the defective interface of sieving fillers in MMMs and the instability to permeate molecules, resulting in instability and degradation in the membrane state and pervaporation performance. Herein, we synthesized defective UiO-66 (DUiO66) by controlling the concentration of the reactants and then analyzed the characteristics of the defects. We confirmed that defects of the missing linker are induced in its structure, and DUiO66 (1.324) has a higher defect density than conventional UiO66 (1.064). Those led to the highly enhanced interface of DUiO66 with polyvinyl alcohol (PVA) matrix and water solvent, resulting in mechanical stability and a uniformed thin selective layer. Crosslinked thin-layered PVA MMMs with DUiO66 (XPDUiO66) were applied to the flat-sheet type and hollow fiber type membranes and then examined for the pervaporation performance to separate IPA/water solution (mainly 80/20 and 90/10 (w/w)). The thin-layered flat type and hollow fiber type XPDUiO66 revealed a dramatic increase in flux by 5.6 and 5.0 times compared to the free-standing type MMM while almost maintaining selectivity. Notably, the flat-sheet type XPDUiO66-2 increased around 606% and 1,664% in PSI relative to XPVA at a feed solution of 80/20 and 90/10 (w/w) IPA/water, respectively. The current work offers significant findings on the relationship between defective MOF-applied MMMs and pervaporation performance.

Study on High-Performance Pervaporation Desalination Membranes Prepared by Interfacial Reactions between Two Aqueous Monomers

Study on High-Performance Pervaporation Desalination Membranes Prepared by Interfacial Reactions between Two Aqueous Monomers

MOFs and COFs based pervaporation membranes for alcohols/water separation: A review

High-performance pervaporation membrane has great application and development potential in alcohols/water separation industry due to its high efficiency and economy. It is an important pathway to alleviate the fossil energy crisis and obtain various alcohols scientifically. As a new type of porous crystal material, metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) with controllable pore structure and rich chemical functions are promising for constructing high-performance alcohols/water separation membranes for future manufacturing development. There are different types of MOFs and COFs based pervaporation membranes, including MOFs polycrystalline membranes, MOFs based mixed matrix membranes (MMMs), COFs continuous membranes, and COFs based MMMs. In this review, we firstly discuss the classification of membranes, describe the process mechanism and evaluation indicators of pervaporation, select decisive criterions for MOFs and COFs, summary the preparation strategies and separation performance of these four membranes, and discuss in detail the impact of operating conditions. Finally, the advantages and disadvantages of these four kinds of membranes are summarized, the challenges faced are identified, and the future development direction is pointed out, aiming to provide slight guidance for the design and development of high-performance MOFs and COFs based membranes for alcohols/water separation in the future.

Preparation of high-performance zeolite membrane on a macroporous support by novel intermittent hydrothermal synthesis

Constructing high-quality zeolite membrane by regulating solely the kinetics of zeolite nucleation and growth is desired because of its simplicity and potential industrial viability. Herein, a high-performance mordenite membrane was prepared without using organic template successfully on a macroporous tubular α-alumina support using a novel and simple intermittent hydrothermal synthesis (IHS) method. We aimed at regulating membrane synthesis kinetics by adjusting the concentration of the synthetic gel by introducing an unheated period of the oven in the middle stage of the synthesis process. In the proposed IHS method, the power supply of the oven can be switched off and on with the aid of a smart socket without manual operation, ensuring its feasibility and convenience. A thin and dense membrane layer was formed via the appropriate adjustment of presynthesis time, unheated time, and resynthesis time. The effects of each duration on the morphologies, microstructures, and pervaporation performances of the prepared mordenite membranes were investigated. Under optimized conditions, the as-synthesized mordenite membrane showed high pervaporation performance with a permeation flux and separation factor of 5.57 kg m−2 h−1 and >10000, respectively, in the dehydration of 90 wt% isopropanol/water mixture at 75 °C. This work provides a novel, simple, and feasible method for the preparation of high-performance zeolite membrane.

High-/Low-Molecular-Weight PDMS Photo-Copolymerized Membranes for Ethanol Recovery

Poly(dimethylsiloxane) (PDMS) is the benchmark of alcohol-selective membranes. The low-molecular-weight PDMS easily causes pore penetration and nonuniform coverage, thus PDMS membrane is generally fabricated by the high-molecular-weight chains (Mw ≥ 50,000). However, there are inevitably excessive chain entanglements in longer polymeric chains, limiting the transport of penetrating molecules. In this work, we proposed a high-/low-molecular-weight PDMS photo-copolymerized strategy to prepare a high-performance pervaporation membrane for ethanol recovery, which combines the advantages of high-/low-molecular-weight PDMS chains. The fluidity and polymerization efficiency are improved, while the excessive pore penetration is prevented. The result showed that the high-/low-molecular-weight PDMS mixed membranes display a superior comprehensive pervaporation performance for ethanol recovery in comparison with the other polymeric membranes. The copolymerized strategy is facile and shows a promising prospect for ethanol recovery.

Designing high-performance pervaporation membranes with hierarchical hydrophobic-hydrophilic coating layers

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.

Liquid-liquid interface induced high-flux PEBA pervaporation membrane for ethanol recovery

Bioethanol has achieved increasing attention in alleviating energy crisis and environmental issues. Pervaporation could be a promising technology to separate ethanol from fermentation. Traditionally, the liquid polymetric solution was compounded on solid porous supports to form composite membranes. Through this liquid-solid interface, it is challenging to precisely control the structure and achieve high pervaporation performance. In this work, we aimed to overcome some of these limitations and designed a polyether block amide (PEBA) pervaporation membrane by dropping the membrane solution on a water surface. While the membrane solution spreading, solvent-water exchange and solvent evaporation occurred. Thereafter the polymer precipitation was induced in the solvent-water interface. The defect-free and uniform selective layer with a thickness of 3.9 μm was achieved by optimizing the ratio of solvent, and the temperature of the water. The PEBA layer was deposited onto porous polytetrafluoroethylene (PTFE) substrate for recovering ethanol from water by pervaporation. The membrane represented a total flux and separation factor of 3.9 kg m−2 h−1 and 4.9, which was maintained stable for 100 h. The interface-induced membrane demonstrated high separation performance and membrane stability.

Breakthroughs on tailoring membrane materials for ethanol recovery by pervaporation

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

Highly flexible and superhydrophobic MOF nanosheet membrane for ultrafast alcohol-water separation.

High-performance pervaporation membranes have potential in industrial separation applications, but overcoming the permeability-selectivity trade-off is a challenge. We report a strategy to create highly flexible metal-organic framework nanosheet (MOF-NS) membranes with a faveolate structure on polymer substrates for alcohol-water separation. The controlled growth followed by a surface-coating method effectively produced flexible and defect-free superhydrophobic MOF-NS membranes. The reversible deformation of the flexible MOF-NS and the vertical interlamellar pathways were captured with electron microscopy. Molecular simulations confirmed the structure and revealed transport mechanism. The ultrafast transport channels in MOF-NS exhibited an ultrahigh flux and a separation factor of 8.9 in the pervaporation of 5 weight % ethanol-water at 40°C, which can be used for biofuel recovery. MOF-NS and polydimethylsiloxane synergistically contribute to the separation performance.

Silica hollow spheres-based superhydrophobic PDMS composite membrane for enhanced acetone permselective pervaporation

Superhydrophobic mixed matrix membranes (SMMMs) are very desirable for efficient separation of biofuel recovery from the fermentation broth via pervaporation.In this work, hydrophobic silica hollow spheres (SHSs) were elaborately prepared by template method and subsequent silane modification. The resulting SHSs were incorporated into polydimethylsiloxane (PDMS) matrix to construct superhydrophobic SHSs/PDMS MMMs. The superhydrophobic composite membrane with 15 wt% SHS contents showed a water contact angle of up to 160°, with low sliding angle of less than 5°. As a result, for the permselective pervaporation of 1 wt% acetone aqueous solution at 35 °C, the optimized composite membrane with separation factor of 46 increased by 256%, and maintained a comparable total flux compared with the pure PDMS membrane. The slight decrease of the total flux was mainly attributed to the reduced water partial flux resulting from water repellency of the superhydrophobic membrane surface. Thus, our proposed strategy of constructing superhydrophobic composite membranes may provide new insights into the development of high-performance pervaporation membrane for biofuel recovery.

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

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

Techno-economic assessment of pervaporation desalination of hypersaline water

The development of pervaporation desalination has seen continuous interest due to the ability of this technology to handle high salinity feeds in the absence of high hydraulic pressure. As pervaporation utilizes the difference of partial vapor pressure as the main driving force for separation, an elevated feed temperature is often needed, and this significantly increases the energy requirements of pervaporation desalination. The advancement of high-performance pervaporation desalination membranes with high water flux and salt rejection in recent years could make this desalination technology competitive to other hypersaline desalination processes. Unfortunately, there is a lack of understanding of the energy requirements necessary for an economic assessment of pervaporation desalination applied for highly saline feed solutions. In this study, the energy requirements and the economic feasibility of pervaporation desalination for hypersaline desalination were evaluated using previously developed high-performance cellulose triacetate/cellulose nanocrystals nanocomposite membranes as the membrane model. The results showed that thermal energy was still the main factor that determined the overall water production cost. Increasing the plant capacity decreased the water cost while increasing the feed salinity from 90 to 200 g L−1 increased the water production cost due to the drop of the water production rate, which requires to expand the membrane surface area to obtain the same plant capacity. A series configuration showed the lowest thermal energy compared to a single and parallel configuration. However, the single configuration is more attractive than a series and parallel configuration when the pervaporation desalination utilized free low-grade waste heat. Hence, PV desalination for treating hypersaline water can be competitive if the process could be integrated with low-grade waste heat from industrial plants as a thermal energy source.

Synthesis a low template B-ZSM-5 membrane with suitable morphology and high performance for the separation of acetone/water mixtures

Synthesizing zeolite membrane using a templating method is often expensive and consumes a lot of energy. Therefore, the synthesis of a high quality B-ZSM-5 zeolite membrane using a low organic template would be required. Here, the synthesis of the low-template B-ZSM-5 zeolite membrane was performed on the surface of α-alumina support modified by TiO2-Bohemite via secondary growth technique under the optimized seeding conditions. A multi-objective optimization method was utilized to identify the optimal support seeding parameters to enhance the performance of the synthesized membrane. Optimization of seeding conditions leads to achieving well intergrowth zeolite membrane with the low template by applying fewer layers. The prepared membrane with a thickness of less than 10 μm showed a high pervaporation performance with a high acetone/water separation factor of 500 and a total flux of 0.13 kg m−2 h−1 for the 1 wt% acetone/water mixture at 333 K and 260 mmHg. The impacts of feed temperature, permeate pressure, and feed concentration on the pervaporation performance, total fluxes as well as membrane separation factor, were investigated. Our results revealed that the separation factor could be significantly increased by increasing the permeate pressure.