Enhanced flux of polydimethylsiloxane membrane for ethanol permselective pervaporation via incorporation of MIL-53 particles

Rational Design of Superhydrophobic and Flexible Oriented MOF Nanosheet Membrane for Highly Efficient Ethanol-Water Separation

Highly efficient and energy-conserving membrane separation technology holds vast potential for applications in the bioethanol production process. This work reports a strategy for the fast preparation of an oriented and flexible two-dimensional metal-organic framework (MOF) nanosheet membrane by an electrochemical deposition method. The oriented MOF nanosheet membrane growth, followed by spin-coating of polydimethylsiloxane, resulted in an efficiently formed superhydrophobic and ethanol affinity membrane for separating ethanol from aqueous solution. Vertically aligned MOF nanosheets with strong ethanol affinity and superhydrophobic membrane surfaces simultaneously promote the transport process, thus delivering a relatively high flux of 1.63 kg·m-2·h-1 and good separation factor of 14.89 in the pervaporation of 5 wt % ethanol aqueous solution. The oriented arrangement of MOF nanosheets combined with polydimethylsiloxane can significantly enhance the pervaporation selectivity and flux, creating a preferential pathway for the production of biofuel.

MOF@MXene nanocomposite as a novel modifier to extend the application of PES mixed-matrix nanofiltration membranes for water treatment

MXene-based membranes, as a type of modified membrane, have unique structures that attract attention for water treatment but suffer from low water flux. To address this, MXene was manipulated with UiO-66-NH2 nanoparticles to create UiO-66-NH2@MXene 2D-nanocomposites for the modification of the PES membrane. Herein, we synthesized a novel modified MXene-based PES membrane. The MXene, UiO-66-NH2, and UiO-66-NH2@MXene were assessed using the Fourier transform infrared, X-ray diffraction pattern, X-ray photoelectron spectroscopy, and zeta potential analysis. Field emission scanning electron microscopy was used to evaluate the MXene-based materials and prepared membranes, and the surface topography of the fabricated membranes was studied using atomic force microscopy. The membrane modified by 0.25 wt% of modifier was able to not only remove 72% and 81% of methylene blue and crystal violet cationic dyes, but also recorded more than 91% rejections for methyl blue, methyl orange, acid fusion, and Congo red anionic dyes. Using the same membrane, salt rejections of 91%, 87%, 79%, and 62% were achieved for Na2SO4, MgSO4, MgCl2, and NaCl, respectively. Water flux was also increased by more than 4 times in the membrane modified with 0.25 wt% of the novel nanocomposite modifier, and the water contact angle of the membrane with 0.5 wt% decreased from 65° to 38° compared to the pristine PES membrane. Besides, the anti-fouling properties were exceptionally improved in the membranes modified by the introduced UiO-66-NH2@MXene nanocomposite modifier.

MOF-Based Membranes for Remediated Application of Water Pollution

Membrane separation plays a crucial role in the current increasingly complex energy environment. Membranes prepared by metal-organic framework (MOF) materials usually possess unique advantages in common, such as uniform pore size, ultra-high porosity, enhanced selectivity and throughput, and excellent adsorption property, which have been contributed to the separation fields. In this comprehensive review, we summarize various designs and synthesized strategies of free-standing MOF and composite MOF-based membranes for water treatment. Special emphases are given not only on the effects of MOF on membrane performance, removal efficiencies, and elimination mechanisms, but also on the importance of MOF-based membranes for the applications of oily and micro-pollutant removal, adsorption, separation, and catalysis. The challenges and opportunities in the future for the industrial implementation of MOF-based membranes are also discussed.

Modified hydrophobic and oleophilic polyurethane sponge for oil absorption with MIL-53

A hydrophobic composite sponge (HPCS) is developed for the first time using the dip coating and drying method in an effort to remove organic contaminants like toluene and various oils from water. We employed a polyurethane (PU) sponge, which is reasonably priced, easily accessible, high mechanical strength and a suitable porous substrate on which the hydrophobic composite of MIL-53(Al) along with PDMS was anchored. A crystalline metal organic framework (MOF), MIL-53(Al), with adjustable porosity, functionality, and hydrophobicity is used for oil absorption. Polydimethylsiloxane (PDMS) is utilized to increase the hydrophobicity of MIL-53(Al). The MIL-53(Al)@PDMS composite was used to the produce a sponge having high hydrophobicity and oleophilicity. In contrast to PU sponge, which has a low water contact angle (79.64°), the hydrophobic composite sponge showed a wide range of oil absorption capacity (12-50.5 g/g), a very low amount of water absorption (0.84 g/g), and water contact angle of 128.13°. This hydrophobic composite performed phenomenally by separating out various oils and solvents from water even in varying ionic strengths. Moreover, the recyclability of the formed composite was also performed resulting into 6-20 cycles for different oils and solvents. The synthesized hydrophobic composite sponge was characterized using FT-IR, XRD, TEM, surface area analysis, FESEM, XPS, TG analysis and contact angle measurement. Furthermore, the materials used in the synthesis of composite are non-toxic and do not harm the environment, resulting in no greenhouse gas emissions making our composite environmentally friendly.

Fabrication and Characterization of Carbon Nanotube Filled PDMS Hybrid Membranes for Enhanced Ethanol Recovery

Ethanol separation via the pervaporation process has shown growing application potential in solvent recovery and the bioethanol industry. In the continuous pervaporation process, polymeric membranes such as hydrophobic polydimethylsiloxane (PDMS) have been developed to enrich/separate ethanol from dilute aqueous solutions. However, its practical application remains largely limited due to the relatively low separation efficiency, especially in selectivity. In view of this, hydrophobic carbon nanotube (CNT) filled PDMS mixed matrix membranes (MMMs) aimed at high-efficiency ethanol recovery were fabricated in this work. The filler K-MWCNTs was prepared by functionalizing MWCNT-NH₂ with epoxy-containing silane coupling agent (KH560) to improve the affinity between fillers and PDMS matrix. With K-MWCNT loading increased from 1 wt % to 10 wt %, membranes showed higher surface roughness and water contact angle was improved from 115° to 130°. The swelling degree of K-MWCNT/PDMS MMMs (2 wt %) in water were also reduced from 10 wt % to 2.5 wt %. Pervaporation performance for K-MWCNT/PDMS MMMs under varied feed concentrations and temperatures were evaluated. The results supported that the K-MWCNT/PDMS MMMs at 2 wt % K-MWCNT loading showed the optimum separation performance (compared with pure PDMS membranes), with the separation factor improved from 9.1 to 10.4, and the permeate flux increased by 50% (40-60 °C, at 6 wt % feed ethanol concentration). This work provides a promising method for preparing a PDMS composite with both high permeate flux and selectivity, which showed great potential for bioethanol production and alcohol separation in industry.

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.

Pervaporation Polyvinyl Alcohol Membranes Modified with Zr-Based Metal Organic Frameworks for Isopropanol Dehydration

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.

Pervaporation as a Successful Tool in the Treatment of Industrial Liquid Mixtures

Pervaporation is one of the most active topics in membrane research, and it has time and again proven to be an essential component for chemical separation. It has been employed in the removal of impurities from raw materials, separation of products and by-products after reaction, and separation of pollutants from water. Given the global problem of water pollution, this approach is efficient in removing hazardous substances from water bodies. Conventional processes are based on thermodynamic equilibria involving a phase transition such as distillation and liquid-liquid extraction. These techniques have a relatively low efficacy and nowadays they are not recommended because it is not sustainable in terms of energy consumption and/or waste generation. Pervaporation emerged in the 1980s and is now becoming a popular membrane separation technology because of its intrinsic features such as low energy requirements, cheap separation costs, and good quality product output. The focus of this review is on current developments in pervaporation, mass transport in membranes, material selection, fabrication and characterization techniques, and applications of various membranes in the separation of chemicals from water.

Recent Advances of Pervaporation Separation in DMF/H2O Solutions: A Review

N,N-dimethylformamide (DMF) is a commonly-used solvent in industry and pharmaceutics for extracting acetylene and fabricating polyacrylonitrile fibers. It is also a starting material for a variety of intermediates such as esters, pyrimidines or chlordimeforms. However, after being used, DMF can be form 5–25% spent liquors (mass fraction) that are difficult to recycle with distillation. From the point of view of energy-efficiency and environment-friendliness, an emergent separation technology, pervaporation, is broadly applied in separation of azeotropic mixtures and organic–organic mixtures, dehydration of aqueous–organic mixtures and removal of trace volatile organic compounds from aqueous solutions. Since the advances in membrane technologies to separate N,N-dimethylformamide solutions have been rarely reviewed before, hence this review mainly discusses the research progress about various membranes in separating N,N-dimethylformamide aqueous solutions. The current state of available membranes in industry and academia, and their potential advantages, limitations and applications are also reviewed.

Novel Pervaporation Membranes Based on Biopolymer Sodium Alginate Modified by FeBTC for Isopropanol Dehydration

Modern society strives for the development of sustainable processes that are aimed at meeting human needs while preserving the environment. Membrane technologies satisfy all the principles of sustainability due to their advantages, such as cost-effectiveness, environmental friendliness, absence of additional reagents and ease of use compared to traditional separation methods. In the present work, novel green membranes based on sodium alginate (SA) modified by a FeBTC metal–organic framework were developed for isopropanol dehydration using a membrane process, pervaporation. Two kinds of SA-FeBTC membranes were developed: (1) untreated membranes and (2) cross-linked membranes with citric acid or phosphoric acid. The structural and physicochemical properties of the developed SA-FeBTC membranes were studied by spectroscopic techniques (FTIR and NMR), microscopic methods (SEM and AFM), thermogravimetric analysis and swelling experiments. The transport properties of developed SA-FeBTC membranes were studied in the pervaporation of water–isopropanol mixtures. Based on membrane transport properties, 15 wt % FeBTC was demonstrated to be the optimal content of the modifier in the SA matrix for the membrane performance. A membrane based on SA modified by 15 wt % FeBTC and cross-linked with citric acid possessed optimal transport properties for the pervaporation of the water–isopropanol mixture (12–100 wt % water): 174–1584 g/(m2 h) permeation flux and 99.99 wt % water content in the permeate.

Membranes for bioethanol production by pervaporation

BACKGROUND

Bioethanol as a renewable energy resource plays an important role in alleviating energy crisis and environmental protection. Pervaporation has achieved increasing attention because of its potential to be a useful way to separate ethanol from the biomass fermentation process.

RESULTS

This overview of ethanol separation via pervaporation primarily concentrates on transport mechanisms, fabrication methods, and membrane materials. The research and development of polymeric, inorganic, and mixed matrix membranes are reviewed from the perspective of membrane materials as well as modification methods. The recovery performance of the existing pervaporation membranes for ethanol solutions is compared, and the approaches to further improve the pervaporation performance are also discussed.

CONCLUSIONS

Overall, exploring the possibility and limitation of the separation performance of PV membranes for ethanol extraction is a long-standing topic. Collectively, the quest is to break the trade-off between membrane permeability and selectivity. Based on the facilitated transport mechanism, further exploration of ethanol-selective membranes may focus on constructing a well-designed microstructure, providing active sites for facilitating the fast transport of ethanol molecules, hence achieving both high selectivity and permeability simultaneously. Finally, it is expected that more and more successful research could be realized into commercial products and this separation process will be deployed in industrial practices in the near future.

Separation and Semi-Empiric Modeling of Ethanol-Water Solutions by Pervaporation Using PDMS Membrane

High energy demand, competitive fuel prices and the need for environmentally friendly processes have led to the constant development of the alcohol industry. Pervaporation is seen as a separation process, with low energy consumption, which has a high potential for application in the fermentation and dehydration of ethanol. This work presents the experimental ethanol recovery by pervaporation and the semi-empirical model of partial fluxes. Total permeate fluxes between 15.6-68.6 mol m-2 h-1 (289-1565 g m-2 h-1), separation factor between 3.4-6.4 and ethanol molar fraction between 16-171 mM (4-35 wt%) were obtained using ethanol feed concentrations between 4-37 mM (1-9 wt%), temperature between 34-50 ∘C and commercial polydimethylsiloxane (PDMS) membrane. From the experimental data a semi-empirical model describing the behavior of partial-permeate fluxes was developed considering the effect of both the temperature and the composition of the feed, and the behavior of the apparent activation energy. Therefore, the model obtained shows a modified Arrhenius-type behavior that calculates with high precision the partial-permeate fluxes. Furthermore, the versatility of the model was demonstrated in process such as ethanol recovery and both ethanol and butanol dehydration.

Dimensional Nanofillers in Mixed Matrix Membranes for Pervaporation Separations: A Review

Pervaporation (PV) has been an intriguing membrane technology for separating liquid mixtures since its commercialization in the 1980s. The design of highly permselective materials used in this respect has made significant improvements in separation properties, such as selectivity, permeability, and long-term stability. Mixed-matrix membranes (MMMs), featuring inorganic fillers dispersed in a polymer matrix to form an organic-inorganic hybrid, have opened up a new avenue to facilely obtain high-performance PV membranes. The combination of inorganic fillers in a polymer matrix endows high flexibility in designing the required separation properties of the membranes, in which various fillers provide specific functions correlated to the separation process. This review discusses recent advances in the use of nanofillers in PV MMMs categorized by dimensions including zero-, one-, two- and three-dimensional nanomaterials. Furthermore, the impact of the nanofillers on the polymer matrix is described to provide in-depth understanding of the structure-performance relationship. Finally, the applications of nanofillers in MMMs for PV separation are summarized.

Metal-Organic Framework Membranes and Membrane Reactors: Versatile Separations and Intensified Processes

Metal-organic frameworks are an emerging and fascinating category of porous solids that can be self-assembled with metal-based cations linked by organic molecules. The unique features of MOFs in porosity (or surface areas), together with their diversity for chemical components and architectures, make MOFs attractive candidates in many applications. MOF membranes represent a long-term endeavor to convert MOF crystals in the lab to potentially industry-available commodities, which, as a promising alternative to distillation, provide a bright future for energy-efficient separation technologies closely related with chemicals, the environment, and energy. The membrane reactor shows a typical intensified process strategy by combining the catalytic reaction with the membrane separation in one unit. This review highlights the recent process of MOF-based membranes and the importance of MOF-based membrane reactors in relative intensified chemical processes.

High-performance pervaporation chitosan-based membranes: new insights and perspectives

Today, the need of replacing synthetic polymers in the membrane preparation for diverse pervaporation (PV) applications has been recognized collectively and scientifically. Chitosan (CS), a bio-polymer, has been studied and proposed to achieve this goal especially in specific azeotropic water-organic, organic-water, and organic-organic separations, as well as in assisting specific processes (e.g. seawater desalination and chemical reactions). Different concepts of CS-based membranes have been developed, which include material blending and composite and mixed matrix membranes which have been tested for different separations. Hereby, the goal of this review is to provide a critical overview of the ongoing CS-based membrane developments, paying a special attention to the most relevant findings and results in the field. Furthermore, future trends of CS-based membranes in PV technology are presented, as well as concluding remarks and suggested strategies for the new scientist in the field.

Pervaporation-based membrane processes for the production of non-alcoholic beverages

Nowadays, the interest in manufacturing non-alcoholic or low alcoholic content beverages from alcoholic beverages is a current challenge for food technologists; this is due to the fact that huge consumption of alcoholic beverages may produce health problems in the costumers. In principle, the post-fermentation ethanol removal from alcoholic beverages is carried out by means of evaporation or distillation. Such current dealcoholization methodologies are efficiently removing the ethanol, however, some organoleptic compounds can also be lost during the process. This makes the dealcoholization process highly sensitive in order to preserve the quality properties of the beverages. Thereby, membrane-based technologies, which use perm-selective barriers for the separation, have been highly promoted for such purpose. Pervaporation (PV) technology is indeed one of these technologies aimed for ethanol removal. Herein, the goal of this review is to provide a compelling overview of the most relevant findings for the production of non-alcoholic beverages (such as beer and wine) by means of PV. Particular attention is paid to experimental results which provide compelling feedback about the accurate ethanol removal and minimal changes on physicochemical properties of the beverages. Moreover, some theoretical basis of such technology, as well as key criteria for a more efficient dealcoholization, are also given.