Composite Pervaporation Membranes Research Articles

Fabrication and performance optimization of an advanced pervaporation desalination membrane: A study utilizing PVDF and hydrophilic active layer as composite

Pervaporation emerges as a promising technique for brine treatment. In this investigation, we employed a PVDF substrate layer and applied various coating solutions using a simple spray technique to produce a composite pervaporation membrane. The composite membrane's chemical structure, morphology, hydrophilicity, swelling property, surface roughness, and crosslinking conditions were thoroughly investigated. Notably, the PVDF/PEI/P(SS-MA) composite membrane exhibited outstanding desalination performance, demonstrating high salt rejection and flux of 308.7 ± 13.8 kg m−2 h−1 when subjected to a 3.5 wt% sodium chloride solution. Even at an elevated brine concentration of 20 wt%, the membrane maintained a commendable flux of 88.76 ± 5.4 kg m−2 h−1 at 72 °C. These findings underscore the efficacy of the developed composite membrane for brine desalination applications.

A review on the design and fabrication of polydimethylsiloxane thin-film composite membranes (TFCMs) for alcohol permselective pervaporation

Pervaporation-based membrane technology have gained increasing interest due to their energy efficiency and environmental sustainability. Polydimethylsiloxane (PDMS) thin-film composite membranes (TFCMs) have emerged as promising candidates for alcohol permselective applications. Compared to the development of pervaporation membrane for water purification, the optimization progress with the ethanol recovery membrane has been fairly slow and fails to meet requirements of bio-alcohol production. Despite the continuous efforts on membrane materials, the role of structural, physicochemical properties for the forming progress of selective layer on substrate is not a well-attended topic. This paper summarized the design and construction considerations of PDMS composite membranes for pervaporation from the viewpoint of the transport resistance model, including the effect of selective layer, support layer, and intermediate layer, to deeply understand and precisely regulate the preparation process. We high light the key role of crosslinking and spreading of PDMS on porous support layer in membrane fabrication. The structure-activity relationship between the separation performance of transport structure with the membrane solution properties, substrate pore structure, and the fabrication methods was discussed in detail. It was indicated that the challenges for the TFCMs applied on a pilot or industrial scale include the thickness control, coating and curing time optimization, and solvent issue. Finally, it was expected for further research to optimize the membrane fabrication process, develop novel advanced membrane materials and to explore complex and potential applications the new requirements in industry.

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

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

Recent Development Based on 2D Composite Membrane for Pervaporation

Recent Development Based on 2D Composite Membrane for Pervaporation

Effect of Phase Heterogeneity on the Properties of Poly(vinyl alcohol)-Based Composite Pervaporation Membranes.

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.

2D Co-UMOFNs filled PEBA composite membranes for pervaporation of phenol solution

Two-dimensional Co ultrathin metal–organic framework nanosheets (Co-UMOFNs) were synthesized and blended into poly (ether block amide) (PEBA) to prepare composite mixed matrix membranes on PVDF supports for the pervaporation of phenol aqueous solution. The membranes were characterized by XRD, ATR-IR, TGA, CA and SEM measurements. Effects of the Co-UMOFNs loading, feed temperature and feed concentration on phenol separation performance were investigated. The results showed that Co-UMOFNs have a two-dimensional layered morphology and have good compatibility with the PEBA. A “brick and mortar” architecture morphology was achieved after incorporating Co-UMOFNs into the PEBA membrane. The amorphous PE segments in the PEBA were turned into a crystalline structure, restricting the motion of PE segments. The filling of Co-UMOFNs slightly improved the thermal stability and hydrophobicity as well. With the increase of the Co-UMOFNs loading from 0% to 40%, the phenol separation factor increased from 27 to 45, and the total flux decreased from 1.2 kg m-2h-1 to 0.42 kg m-2h-1, when separation of 1000 ppm phenol solution at 70 °C. The interlayer galleries induced by the Co-UMOFNs stacking increased the tortuosity, and the crystalline structure of the Co-UMOFNs-PEBA improved the energy barriers of water penetration. Therefore the water flux was inhibited and the phenol separation factor increased. Depression of water permeation can be another protocol to prepare high-performance organophilic pervaporation membranes.

Ionically cross-linked sodium alginate and polyamidoamine dendrimers for ethanol/water separation through pervaporation

The pervaporation process is an energy-conservative and environmentally friendly method to separate organic solvent from water. It efficiently separates close boiling point and azeotrope mixtures unlike the distillation process. Herein, primary amine-terminated polyamidoamine (PAMAM) dendrimers are proposed to interact with the highly hydrophilic and negatively charged sodium alginate (SA) polymer chains for the preparation of pervaporation composite membranes. Different generations of PAMAM dendrimer (G0, G1, and G2) have different number of terminal primary groups (P4, P8, and P16). That is, a higher generation number means there are more terminal amine groups available for interaction. The addition of PAMAM contributed to the stronger hydrogen bonding of SA and inhibited the swelling of pristine SA/PVDF composite membranes. Interestingly, the free volume characteristics of the SA/PVDF membranes with PAMAM altered the number and size of the free volume spaces as confirmed by positron annihilation spectroscopy (PAS). The more terminal primary amine groups of PAMAM resulted to a higher ionic interaction with the sodium alginate polymer chains producing a denser structure. The denser structure of SA-P8/PVDF and SA-P16/PVDF resulted to a lower flux than with SA-P4/PVDF. The SA-P4/PVSDF at 40 ppm loading achieved the highest separation performance for the dehydration of 90/10 wt% ethanol/water mixture at 25 °C with a permeation flux of 1,039 g m-2h−1 and a water concentration in permeate of 99.41 wt%. Furthermore, the SA-P4/PVDF membrane can withstand high water content in feed up to 50 wt% and high operating temperature of 70 °C showing enhanced stability of the selective layer due to the interactions between SA and PAMAM dendrimer.

Pressure effect during the formation of a selective layer on the structure and performance of dynamic composite membranes for pervaporation

Composite membranes for pervaporation were prepared by forming a selective layer based on cross-linked polyvinyl alcohol (PVA) on the porous membrane-substrate surface in the dynamic mode (via PVA solution ultrafiltration). It was found that the pressure growth results in increasing the thickness of the composite membrane selective layer. Composite membrane contact angle, flux, water content in permeate in ethanol/water (mass ratio 90/10) pervaporation were revealed to have maximum values at 3–4 atm depending on the PVA concentration in the feed solution. It was shown that the revealed dependence of the contact angle, selectivity, and permeability on the pressure of the selective layer formation is due to the compaction of the polymer matrix-substrate under the action of the transmembrane pressure and its relaxation after pressure release. When using elevated pressures (more than 3–4 atm), the relaxation of the polymer matrix causes the microdefect to form as a result of deformation of the selective layer.

Mass transport and pervaporation recovery of aniline with high-purity from dilute aqueous solution by PEBA/PVDF composite membranes

Poly(ether block amide)(PEBA)/poly(vinylidene fluoride)(PVDF) composite pervaporation membrane was prepared for recovering of high-purity aniline from dilute aqueous solution, and the resistance-in-series model was set up for the simulation of the present pervaporation. Based on the mass transport model, the thickness of PEBA selective layer was determined by considering the boundary concentration polarization. It is found that the selective layer membrane with a thickness of 20 μm would almost have no diffusion barrier in the liquid phase at 80 °C when Re was above 1000. Meanwhile, based on the studies on the effects of feed concentration as well as temperature on the separation performance of PEBA/PVDF composite membrane in terms of permeation flux, selectivity and permeance, it is also found that the total permeation flux could reach as high as 6420 g/(m2 h) with a corresponding separation factor of 35 at a feed concentration of 3 wt% and a feed temperature of 80 °C, indicating the excellent performance of the as-prepared composite membrane for aniline separation. Furthermore, the performance of the composite membrane for the removal of aniline from wastewater was investigated using a batch pervaporation-fractional condensation (PVFC) experimental system, by which the concentration of the feed could be reduced to 550 ppm after 5.5 h of treatment, and accordingly, 65 wt% of the aniline in the feed was recovered in the first condenser as its high-purity form at an initial aniline concentration of 30,000 ppm.

Development of new pervaporation composite membranes for desalination: Theoretical and experimental investigations

Pervaporation (PV) has mainly been used for dehydration in industrial applications as well as for the recovery of some organic components from various organic or water mixtures. Nevertheless, to date, pervaporation has never been seen as a potential industrial solution to get drinkable water by water permeation, contrarily to membrane distillation (MD). Nevertheless, at the lab scale, some studies with hydrophilic PV membranes have been reported. This work intends to underline the potential industrial interest of hydrophobic PV composite membranes for desalination. Indeed, even in hypersaline solutions, the water activity remains very high (>0.9), and it is wise to use membranes with stable properties in water to guarantee steady performance. Therefore, this study investigates the interest of hydrophobic polymers as coating selective layers for desalination. To guide our choice, a rational approach was used based on the prediction of the membrane resistance to water transfer. Polymethylpentene, poly(1-trimethylsilyl-1-propyne) and Teflon™ AF2400 were tested as the top layer to obtain hydrophobic composite PV membranes. Several feed NaCl solutions with or without a surfactant were used to investigate the mass transfer properties of these PV membranes for water treatment comparatively to more conventional porous membranes (e.g. PVDF) currently studied in membrane distillation.

Sustainable composite pervaporation membranes based on sodium alginate modified by metal organic frameworks for dehydration of isopropanol

Novel dense and supported (polyacrylonitrile substrate) mixed matrix membranes based on biopolymer sodium alginate (SA), modified by Zr-MOFs were developed to improve pervaporation dehydration properties of a parent SA membrane. The following Zr-MOFs were synthesized and tested as modifiers: unmodified UiO-66 and modified UiO-66(NH2)-AcOH and UiO-66(NH2)-EDTA. Two kinds of mixed matrix membranes were developed: without additional treatment and cross-linked with calcium chloride. The synthesized Zr-MOFs nanoparticles and developed SA and SA-Zr-MOFs membranes were studied using Fourier-transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, surface area measurement, atomic force microscopy, X-ray diffraction analysis, thermogravimetric analysis, and swelling experiments. Dense and supported membranes were tested for their transport properties in the pervaporation dehydration of isopropanol (12, 30 wt% water for the untreated membranes and 12–100 wt% water for the cross-linked membranes). The best transport properties (dehydration of water/isopropanol mixtures at 22 °C) were demonstrated by a supported cross-linked membrane, containing 15 wt% of UiO-66: permeation flux 0.47–3.38 kg/(m2h), water content in permeate 99.9-97.5 wt%.

2D Co-UMOFNs Filled PEBA Composite Membranes for Pervaporation of Phenol Solution

2D Co-UMOFNs Filled PEBA Composite Membranes for Pervaporation of Phenol Solution

Concentrating brine for lithium recovery using GO composite pervaporation membranes

The extraction process of highly demanded lithium from brine normally starts with a solar evaporation pond to increase the lithium concentration, which takes more than a year and is weather-dependent. This work evaluated the enrichment of lithium from salt lake brine using graphene oxide (GO) composite pervaporation membrane with the crystallizer unit. The deposition of stacked GO layer on the commercially available hydrophobic membranes can tackle the membrane wetting and salt crystallization issues. The initial water flux was 11 L/m2 h at 70 °C, which was 20 times higher than that of solar evaporation pond (~0.5 L/m2 h) and 10 times lower footprint. With high initial feed concentration (>200 g/L of salt) the GO composite pervaporation membrane increased lithium concentration from 0.3 to 1.27 g/L (73% feed volume reduction). Assuming 10 m3/day capacity of the proposed solar pervaporation system, an economic analysis showed that the technique is not economically sustainable when solely aiming at the lithium extraction, while it becomes competitive with the traditional method when aiming at simultaneously producing deionized water and lithium. A payback time of 3.6–27 years is achievable with the sale price of water and LiOH at US$ 0.3–1 per 20 L and US$ 20 per kg, respectively. A continuous process is also possible with backup gas heater and waste heat.

Improved pervaporation efficiency of thin-film composite polyamide membranes fabricated through acetone-assisted interfacial polymerization

•Promoting the separation efficiency of pervaporation membranes is a must to meet the growing demands of society. In this study, acetone-assisted interfacial polymerization was employed to produce thin-film composite (TFC) pervaporation membranes with improved performance. Two monomers were considered—diethylenetriamine (DETA) and trimesoyl chloride (TMC); they reacted with each other to form a thin polyamide layer, which was deposited on a hydrolyzed polyacrylonitrile (HPAN) substrate. Aqueous solutions containing different concentrations of acetone were used to dissolve DETA. Introducing acetone as a cosolvent of water enhanced the sorption of DETA in the HPAN support. It also altered and improved the physicochemical properties of the TFC membranes. An optimum concentration of 50 wt% aqueous acetone solution was established. Through acetone-assisted interfacial polymerization, a TFC membrane was then fabricated, and it exhibited a high separation efficiency: permeation flux = 1641 ± 134 g∙m−2 h−1 and water concentration in the permeate = 98%–99% (feed =70 wt% aqueous isopropanol solution). Moreover, the modified TFC membrane displayed a high separation performance at a wide range of operating conditions.

High-performance polyamide composite membranes via double-interfacial polymerizations on a nanofibrous substrate for pervaporation dehydration

A novel double-interfacial polymerizations (double-IP) strategy was demonstrated for the maneuverable fabrication of high-performance polyamide (PA) composite membranes based on nanofibrous substrates for efficient isopropanol dehydration by pervaporation. Firstly, an ultra-thin auxiliary polyamide layer (A-PA) was synthesized on a highly porous polyacrylonitrile (PAN) nanofibrous substrate by using low concentration ethylenediamine (EDA) and trimesoyl chloride (TMC) solution, which decreased the reaction rate and prolonged polymerization time to achieve a smooth, relatively loose but intact A-PA layer. Secondly, a more compact PA selective layer (S-PA) was fabricated with relatively high concentration EDA and TMC solution on A-PA surface. Benefiting from the A-PA layer, the amount and diffusion rate of adsorbed EDA solution through the layer to contact TMC solution were effectively controlled in second IP process. S-PA layers tended to be more uniform, and there was no marked void or detachment observed between two PA layers. Significantly, the pervaporation performance of as-prepared membranes were tuned by changing the structure of S-PA layers with the assistant of different A-PA layers. The optimized two-tier polyamide (Bi-PA) thin-film nanofibrous composite (TFNC) pervaporation membranes exhibited high permeate flux (6075 g/(m2 h)) and enhanced separation factor (1314) for dehydrating 90 wt% aqueous isopropanol solution at 70 °C. This work may suggest an efficient and facile approach to fabricate high performance pervaporation membranes.

Surface Properties, Free Volume, and Performance for Thin-Film Composite Pervaporation Membranes Fabricated through Interfacial Polymerization Involving Different Organic Solvents.

The type of organic solvents used in interfacial polymerization affects the surface property, free volume, and separation performance of the thin-film composite (TFC) polyamide membrane. In this study, TFC polyamide membrane was fabricated through interfacial polymerization between diethylenetriamine (DETA) and trimesoyl chloride (TMC). Four types of organic solvent were explored in the preparation of pervaporation membrane. These are tetralin, toluene, hexane, and isopentane. The solubility parameter distance between organic solvents and DETA follows in increasing order: tetralin (17.07 MPa1/2) < toluene (17.31 MPa1/2) < hexane (19.86 MPa1/2) < isopentane (20.43 MPa1/2). Same trend was also observed between the organic solvents and DETA. The larger the solubility parameter distance, the denser and thicker the polyamide. Consequently, field emission scanning electron microscope (FESEM) and positron annihilation spectroscopy (PAS) analysis revealed that TFCisopentane had the thickest polyamide layer. It also delivered the highest pervaporation efficiency (permeation flux = 860 ± 71 g m−2 h−1; water concentration in permeate = 99.2 ± 0.8 wt%; pervaporation separation index = 959,760) at dehydration of 90 wt% aqueous ethanol solution. Furthermore, TFCisopentane also exhibited a high separation efficiency in isopropanol and tert-butanol. Therefore, a suitable organic solvent in preparation of TFC membrane through interfacial polymerization enables high pervaporation efficiency.

Rational tuning of the viscosity of membrane solution for the preparation of sub-micron thick PDMS composite membrane for pervaporation of ethanol-water solution

The cost of polymer membranes significantly affects their industrial applications, which is inversely proportional to their thickness. Hence, to economically realize the industrial applications of polymer membranes, their thickness should be reduced. In this work, a facile and scalable coating method was used to fabricate thin pervaporation composite membranes. The viscosity of the membrane solution and the hydrodynamic diameter of the polymer coil in heptane were optimized. Polydimethylsiloxane/polytetrafluoroethylene composite membranes with thickness as low as 700 nm could be obtained. The composite membranes showed an amorphous structure with almost constant surface hydrophobicity, and a flux as high as 2.4 kg/(m2·h) can be obtained while the separation factor sustains 8.6 at 40 °C for the separation of 5 wt% ethanol-water solution. The effects of the feed pressure, feed temperature, and vapor permeation and substrates on their performance were investigated. Results showed that too low or too high viscosity of membrane solution is not suitable for the formation of the membrane without defects. This also indicated that the coating method developed in this study, using an optimum membrane solution viscosity, is an efficient approach for the large-scale fabrication of sub-micron-thick membranes.

Exploring distillation-pervaporation hybrid process in a single column using hollow fiber pervaporation composite membranes as structured packing

This study developed a novel strategy for azeotrope separation such as ethanol-water binary system. Distillation-pervaporation hybrid process was employed by using hollow fiber pervaporation composite membranes as structured packing in a single hybrid column rather than using pervaporation as an externally connected unit of the distillation column. The separating limitation of azeotrope challenged in conventional distillation could be readily overcome by continually removing water from the hybrid system via pervaporation. The competition between distillation and pervaporation has been found to be cause of unexpected concentration distribution in the hybrid column. The mass flux of mixture decreased with time whereas the selectivity of water to ethanol first increased then decreased with time. Analysis of this system illustrated that the increase in heating power and membrane area shortened time for obtaining certain content of ethanol in the mixture. However, faster decline in mass flux occurred due to an increase in the removal rate of water. With respect to its simplicity, efficiency and broad applicability, this hybrid process is expected to provide a benchmark for the enhancement of distillation-pervaporation process by hollow fiber membrane packing.

The fine-structure characteristics and isopropanol/water dehydration through pervaporation composite membranes improved with graphene quantum dots

The facile synthesis and functionalization of graphene quantum dots (GQDs) have shown benefits in membrane separation processes since it could augment their performance. Here, the fine-structure characteristics and alcohol dehydration performance of a polymeric pervaporation composite membrane integrated with either nitrogen-doped graphene quantum dots (NGQDs) or oxygen-passivated graphene quantum dots (OGQDs) were evaluated. Calcium ion cross-linked sodium alginate (Alg) was used as the polymer matrix since the multiple hydroxyl and carboxyl groups could form hydrogen bonds with GQDs. The interfacial interaction between the two types of GQDs and Alg was evaluated through the pervaporation dehydration of isopropanol/water (i-PrOH/water) mixture and further analyzed using positron annihilation lifetime spectroscopy (PALS). The PALS results revealed that different functionalized GQDs affect the fine-structure characteristics of Alg matrix and resulted to different alcohol dehydration performance. In dry state, both NGQD and OGQD integrated membranes have smaller free volume spaces than the pristine Alg membrane indicating improved interfacial interaction between the GQD and Alg. However, in wet state, larger free volume spaces appeared and it was shown that OGQD integrated membranes have the largest. These data explained the higher permeation flux and separation factor of Alg-OGQD membranes than Alg-NGQD and Alg. The total flux reached to 5580 g m−2h−1 with a water concentration in permeate of ~99.95% in dehydrating i-PrOH/water (70/30 wt%) at 70 °C for Alg-OGQD membrane with 100 ppm of OGQD (Alg-OGQD100). Furthermore, the membrane remained stable for 720 h of operation at 70 °C with a water concentration in permeate >99% showing potential for practical applications.

Alcohol dehydration performance of pervaporation composite membranes with reduced graphene oxide and graphene quantum dots homostructured filler

Graphene quantum dots(GQDs) were used to possibly cover the structural defects on the graphitic regions of reduced graphene oxide(rGO). The resulting homostructure nanocomposite fillers(rGO + GQD) were incorporated in an alginate solution creating a dense composite membrane for pervaporation. The membranes were applied to separate alcohol/water mixtures in which the successful covering of structural defects was observed with good separation performance of lower molecular weight alcohols. The Raman spectra and elemental analyses confirmed the successful changes on the physical and chemical structures of the homostructured fillers. The X-ray diffraction pattern showed that the crystallinity of the membrane was greatly affected when incorporated with rGO + GQD. The alginate incorporated with 3 wt% of rGO + GQD(Alg-rGO + GQD) has the best pervaporation performance in separating methanol/water mixture with a permeation flux of 2323 g m−2 h−1 and water concentration in permeate of 92.7% at 70 °C. While the positron annihilation lifetime spectroscopy results supported that the minimization of the structural defects enhanced the water selectivity of the membrane by easy transport of water molecules through the free volume spaces and blocks methanol molecules. The results in this study may provide the possible sealing or curing the defects on rGO with GQDs and improve the interfacial interaction with the polymer matrix.