Pervaporation Performance Research Articles

Pervaporation removal of methanol from methanol/organic azeotropes using organosilica membranes: Experimental and modeling

Membrane-based separation of organic/organic mixtures is of great importance in the chemical and petrochemical industries, but remains very challenging owing to the harsh working conditions. Herein, ultrathin and chemically stable Bis(triethoxysilyl)acetylene (BTESA)-derived organosilica membranes were reproducibly prepared, and for the first time they were utilized in the pervaporation separation of methanol/organic azeotropes. The as-prepared BTESA membranes exhibited exceptional pervaporation performance in a 10 wt%/90 wt% methanol/dimethyl carbonate (DMC) mixture, and showed a high separation factor of approximately 120 with a permeation flux of 2–4 kg m-2 h-1 at 50 °C. This impressive performance was primarily the result of the preferential sorption of methanol and the efficient size sieving of DMC. In addition, the effects of feed concentration and temperature on methanol/DMC pervaporation performance were thoroughly investigated. Importantly, a generalized solution-diffusion model successfully described the pervaporation performance of BTESA membranes, and the usefulness of this model was further confirmed via the pervaporation of methanol/methyl acetate and methanol/methyl tert-butyl ether (MTBE) mixtures. This work demonstrates the great potential of organosilica membranes for high-performance organic/organic pervaporation.

Comparison of Single and Double-Network PVA Pervaporation Performance: Effect of Operating Temperature

Thermal crosslinking sequential method applied for DN-PVAs generation efficiently. The swelling measurements investigated that the hydrophilicity of the membrane decreases because of the collaboration of the second thermal crosslinked PVA matrix. The dehydration performance of ethanol solution showed improved using the thermal crosslinked double network PVA membrane. The pervaporation dehydration of the water-ethanol mixture was investigated at different conditions. The separation selectivity showed a significant improvement, while the permeation flux declines due to the incorporation of the second PVA network under 95 % ethanol and at 40 °C. Increasing the feed temperature enhanced the permeability of the membrane, while decreasing the water content in the feed resulted in an increase in the selectivity. The overall results showed that, at high operating temperature and high ethanol concentration in the feed, the prepared membranes are highly selective towards the water with reasonable fluxes values. The influence of temperature permeation parameter and diffusion coefficient of the feed component is also discussed. The negative heat of sorption ( ∆Hs ) values calculated on the basis of the estimated Arrhenius activation energy values indicates that the sorption process is controlled by Langmuir's mode.

Separation of bio‐based chemicals using pervaporation

AbstractThe increasing demand of raw materials and the ever‐present risk of fossil resource depletion are effective motivators for the development of new bio‐based routes for the synthesis of chemicals. The use of non‐renewable natural resources, such as fossil fuels, and the generation of greenhouse gases have led to severe environmental problems. However, one of the challenges of using renewable biomass resources to produce building block molecules is achieving an efficient and economically viable purification step. The complexity of the mixture involves generally high separation costs. Separation processes, such as distillation and liquid–liquid extraction, have been proposed to purify target bio‐based compounds. However, the high energetic cost associated with such processes is pushing the current research towards the development of alternative solutions. In this context, membrane technology, such as pervaporation, is an interesting solution for minimizing the energy consumption of the process. This review highlights the main parameters and factors that impact the performance of pervaporation in the separation of complex bio‐based chemical mixtures. Coupling effects, which are among the critical issues in pervaporation, are discussed in detail. Hybrid processes, in which both reaction and distillation are performed during the pervaporation process, are also addressed. © 2020 Society of Chemical Industry

RETRACTED ARTICLE: Novel Branched Polyamide/Poly(acrylonitrile)/Graphene Oxide Membranes for Separation of Chlorinated Volatile Organic Compounds from Water via Pervaporation

Branched polyamides (BPAs) were prepared through a polycondensation method and then blended with poly(acrylonitrile) (PAN; 3:1) to construct the nanocomposite membranes having various concentrations of graphene oxide (GO) (2 and 5 wt%). The BPA/PAN and BPA/PAN/GO membranes were applied for selective removal of chlorinated volatile organic compounds (Cl-VOCs) from water by pervaporation. Impacts of feed composition, GO content and distinct feed types were investigated on pervaporation performance. Membranes were water selective and the permeation rate incremented with GO elevation. The highest permeation rate (203 g/m2 h) and separation factor (10) were detected for BPA/PAN/GO-5 nanocomposite membrane containing 5 wt% GO for separating the pentachloroethane/water mixtures at 30 °C for 0.1 wt% pentachloroethane in feed. Separation of pentachloroethane/water mixture proceeded easier than those of 1,1,1,2-tetrachloroethane/water, trichloroethylene/water, and 1,2-dichloroethylene/water mixtures because of the larger molecular size of pentachloroethane.

Negative impact of butyric acid on butanol recovery by pervaporation with a silicalite-1 membrane from ABE fermentation

In this study, the utilization of silicalite–1 membrane pervaporation for butanol recovery from an acetone-butanol-ethanol (ABE) fermentation broth solution was investigated. In particular, the negative effect of butyric acid on the pervaporation performance was tested. The presence of butyric acid was observed to decrease both the butanol flux and selectivity of the membrane. Clear relation between the severity of the decreased performance and the amount of butyric acid was observed. Increasing the pH of the feed solution was observed to improve butanol pervaporation in the presence of butyric acid. In pervaporation of ethanol, butanol and butyric acid, there are significant interactions in adsorption and diffusion between the components. The presence of butanol restricts the permeation of ethanol while the butanol permeation is restricted by the presence of butyric acid. The effects likely arise from adsorptive competition and are further amplified due to the rates of diffusion. In addition, butyric acid exposure may change the membrane properties over time, although they may be restored by heating. The results suggest that the selective recovery of butanol with a silicalite–1 membrane is not feasible if the concentration of butyric acid is significant and the pH value in the solution is low.

Preparation and characterization of a novel green silica/PVA membrane for water desalination by pervaporation

In this study, silica was extracted from rice husk (RH) waste to develop a novel green silica/PVA hybrid membrane for improving the desalination performance by pervaporation. A thermal method with citric acid leaching was applied for the extraction of green silica under different conditions, and the best high-cost purity silica obtained was incorporated into the PVA membrane with loadings of 0%, 10% and 20%. The effect of the green silica content on the membrane characteristics, desalination performance, and pervaporation temperature was investigated. The purest silica (>97 wt%) was obtained for a 5% acid leaching solution, which was used as the filler in the PVA membrane, and at a combustion temperature of 700 °C. The green silica/PVA membrane exhibited a higher roughness and hydrophilicity and a lower crystallinity compared with pure PVA, indicating an enhancement in the permeation flux. The flux of hybrid membranes reached the maximum value of 12.3 kg m−2h−1 at 60 °C for 10% silica loading with a 3.5 wt% NaCl feed concentration. Salt rejection remained higher than 99.9% for all membranes, and the apparent activation energy showed no significant difference between experiments. The results showed that the pervaporation performance was successfully improved by incorporating the RH silica into the PVA membrane.

A polyvinyl alcohol‐based mixed matrix membrane with uniformly distributed Schiff base network‐1 for ethanol dehydration

AbstractIn this study, Schiff base network (SNW)‐1 nanoparticles with high hydrophilicity and large specific surface area were used to prepare polyvinyl alcohol (PVA)‐based mixed matrix membranes (MMMs), which were evaluated for ethanol dehydration. Because of the low difference of density between SNW‐1 and PVA, the as‐prepared nanoparticles can be uniformly distributed into the PVA active layer. The effects of SNW‐1 loading, feed temperature, and water concentration on pervaporation (PV) performance were further studied. The results showed the MMM with 10 wt% of SNW‐1 loading exhibited a separation factor of 1,501 and a permeation flux of 187 g m−2 h−1 for feeding 95 wt% ethanol/water binary solution at 75°C. Overall, the SNW‐1/PVA MMMs showed great prospect in ethanol dehydration via PV.

Using genipin as a “green” crosslinker to fabricate chitosan membranes for pervaporative dehydration of isopropanol

Chitosan membranes were fabricated using naturally-occurring ecofriendly genipin (GP) as a “green” alternative crosslinking agent to replace conventionally used glutaraldehyde (GA). Both GP- and GA-crosslinked chitosan membranes were tested for pervaporative dehydration of isopropanol and characterized by surface energy analyses. The GP-crosslinked chitosan membranes were demonstrated to compare favorably to GA-crosslinked membranes in terms of membrane permselectivity. At a given content of crosslinking agent in the membrane, GP-crosslinked chitosan membranes showed a higher hydrophilicity than chitosan membranes crosslinked with GA. The effects of crosslinker content and operating conditions (including feed concentration and temperature) on the pervaporation performance for isopropanol dehydration were also investigated. It was revealed that the observed increase in permeation flux with an increase in temperature was primarily due to increased driving force for the permeation, and the membrane permeability to both permeants was actually lowered, to a lesser extent, with an increase in temperature.

Polyrotaxane crosslinked modified EC/PVDF composite membrane displaying simultaneously enhanced pervaporation performance and solvent resistance for benzene/cyclohexane separation

A new strategy was proposed that simultaneously improves the pervaporation (PV) performance and solvent resistance via the construction of a movable crosslinked structure in ethyl cellulose/polyvinylidene fluoride (EC/PVDF) composite membrane for the purpose of benzene/cyclohexane separation. Based on the molecular design of the macrocyclic compound cyclodextrin, polyrotaxane crosslinking agent (PR=) with a special sliding/rotating property and cavity structure was successfully synthesized. Furthermore, for convenient comparative study, cyclodextrin crosslinking agent (CD=) with cavity structure bereft of a sliding/rotating property and pentaerythritol triacrylate (PETA) without sliding/rotating property and cavity structure were prepared. The composite membranes were fabricated with crosslinking modified EC as active layer, together with PVDF support layer. The molecular structure and microstructure were confirmed. The pervaporation and swelling performance of the fabricated membranes for benzene/cyclohexane were investigated. PR= modified membranes showed good solvent resistance and exhibited a flux of 4332 g·m−2·h−1 and separation factor of 6.26, which was higher than CD= and PETA modified membranes. The results were attributed to the facilitated transport behavior, which was markedly related with the sliding/rotating property and cavity structure of polyrotaxane (PR). The related research provides interesting suggestions for PV membrane design for the separation of organic mixtures.

Pervaporation Performance of Polydimethylsiloxane-Polyvinylidene Fluoride Composite Membrane for Butanol Recovery from Model Solutions and Acetone-Butanol-Ethanol Fermentation Broth

Pervaporation has been identified as the most promising separation technology for butanol recovery in acetone-butanol-ethanol (ABE) fermentation, to overcome two main obstacles, low yield and high separation cost in the industrial-scale butanol production. In this work, we investigated the pervaporation performance of a thin flat polydimethylsiloxane (PDMS)-polyvinylidene fluoride (PVDF) composite membrane for butanol recovery from model solutions and ABE fermentation broth. The PDMS-PVDF composite membrane exhibited a high total flux of 1330 g m–2 h–1, and relatively higher separation factors of 21.2, 17.2, and 4.5 for acetone, butanol, and ethanol, respectively, with ABE-water solution. Compared to ABE-water solution, the total flux decreased by 3.25% and separation factors increased by 1.40%, 3.21%, and 3.92% for acetone, butanol, and ethanol in ABE fermentation broth, indicating that the negative effect of impermeable components present in the ABE fermentation broth was negligible. The excellent pervaporation performance and long-term operational stability of PDMS-PVDF composite membrane can enhance the efficacy of butanol recovery, thus it has potential to be used as a competitive pervaporation membrane in ABE fermentation process.

Poly(vinyl alcohol)-Modified Membranes by Ti3C2T x for Ethanol Dehydration via Pervaporation.

In this paper, PVA/Ti3C2Tx mixed matrix membranes (MMMs) were prepared by mixing the synthesized Ti3C2Tx with the PVA matrix, and the pervaporation (PV) performance of the ethanol–water binary system was tested. The morphology, structural properties, and surface characteristics of the membranes were investigated by scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, degree of swelling, and water contact angle. The PVA/Ti3C2Tx MMMs exhibit excellent compatibility and swelling resistance. Moreover the effects of the Ti3C2Tx filling level, feed concentration, and operating temperature on the ethanol dehydration performance were systematically studied. The results demonstrated that the separation factor of PVA/Ti3C2Tx MMMs was significantly increased because of Ti3C2Tx promoting the cross-linking density of the membrane. Specifically, the membrane showed the best PV performance when Ti3C2Tx loading was 3.0 wt %, achieving a separation factor of 2585 and a suitable total flux of 0.074 kg/m2 h for separating 93 wt % ethanol solution at 37 °C.

Enhancement in pervaporative performance of PDMS membrane for separation of styrene from wastewater by hybridizing with reduced graphene oxide

The removal of styrene from wastewater by pervaporation was investigated by using composite PDMS membranes filled with reduced graphene oxide on PES support layers. Graphene oxide was synthesized through modified Hummers' method and then chemically reduced. The filler was characterized by TEM, SEM, XRD, and AFM. The top layers with different PDMS molecular weights were cast on the PES supports, which were prepared by phase inversion method. The characterizations of prepared membranes were investigated by SEM, AFM, contact angle measurement, TGA, and DSC. It was observed that presence of the filler in the polymeric matrix controls the swelling of the membrane and enhances its solubility parameter in favor of styrene. Moreover, it significantly improves the thermal stability of the membranes. The mechanism of separation in the process was found to be affected mainly by enhancing in the membrane's solubility rather than in its diffusivity. The pervaporative performance of prepared membranes showed their great affinity toward styrene so that the separation factor of the optimum membrane (M2/S) was increased about 250% (600.4 in comparison to 241.4 for the unfilled membrane) while its total flux was decreased from 772.5 g m−2.h−1for the unfilled membrane to 321.9 g m−2.h−1. Increasing the molecular weight of PDMS lowered the optimal rGO content due to the complexity of the diffusion path and occupation of free volume by longer polymer chains. Accordingly, a lower total flux (124.7 g m−2.h−1 for high MW compared to 718.0 g m−2.h−1 for low MW) and higher separation factor (822.5 for high MW compared to 230.8 for low MW) were yielded for the same filler content (0.1 wt% rGO).

Preparation of hybrid membranes by incorporating hydrophilic UiO-66 nanoparticles for high-performance pervaporation dehydration of aprotic solvents

Hydrophilic UiO-66 crystals with superior water adsorption ability were synthesized and incorporated into the polyimide (PI) membrane for efficient aprotic solvent separation via pervaporation. The effect of the different UiO-66 addition in the pyromellitic dianhydride (PMDA)-2, 2-bis[4-(4-amlnophenoxy)phenyl]propane (BAPP)-based PI membrane on the membrane structure, thermal stability, surface hydrophilicity, solvent-resistant, and pervaporation performance was systematically studied. The UiO-66/PI hybrid membranes with small amount content (2 wt%) exhibited high hydrophilicity and excellent swelling resistance due to the superb dispersion benefiting from the excellent complexation of UiO-66 and PI chain. The effects of operational variables such as operating temperature and concentration of feed solution on the pervaporation separation performance of the hybrid membranes with different UiO-66 loadings were investigated. When the mass fraction of UiO-66 was 2 wt%, the hybrid membranes show the permeation flux of 109.7 and 57.1 g/(m2h) and separation factor of 34.1 and 133.9, respectively, for DMF/H2O and DMAc/H2O systems.

Manipulation on microstructure of MFI membranes by binary structure directing agents

Abstract The good quality pure-silica MFI zeolite membrane with hydrophobic surface was fabricated by the addition of TBABr in “TEOS-TPAOH-H2O” synthesis solution. The effects of TBABr on PV performance and the microstructure of MFI membranes were explored by pervaporation, single-component gas permeation, water contact angle, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS) and 13C solid state CP MAS NMR. It was found that small amounts of TBABr could accelerate the growth and contribute to compact membranes with high bulk Si/Al ratio and good hydrophobic surface, hence resulting in better pervaporation performance. Excessive amounts of TBABr would interfere the crystallization and result in lower pervaporation performance. For example, when the TBABr/Si ratio increased to 0.01 from 0 with the TPAOH/Si ratio of 0.09, the membrane separation factor was increased from 35 to 59 with the flux of 1.85 kg m−2 h−1 for 5 wt% of ethanol/water mixtures at 60 °C.

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.

Improved Desulfurization Performance of Polyethyleneglycol Membrane by Incorporating Metal Organic Framework CuBTC.

In this paper, copper benzene-1,3,5-tricarboxylate (CuBTC) was incorporated into polyethylenglyol (PEG) to prepare a mixed matrix membrane (MMM) for pervaporation desulfurization. The characterization results showed that the prepared CuBTC particles had an ideal octahedral shape and micropores. The Cu2+ in CuBTC interacts with thiophene via π-complexation, thus enhancing the separation performance of the hybrid membranes. The effect of CuBTC content and the operating condition on the pervaporation performance of the MMMs was investigated. An optimal pervaporation separation performance was acquired with a permeation flux of 2.21 kg/(m2·h) and an enrichment factor of 8.79, which were increased by 100% and 39% compared with the pristine PEG membrane. Moreover, the CuBTC-filled PEG membrane showed a good stability in the long-term desulfurization under a high operating temperature of 75 °C for five days.

Fabrication and characterization of superhydrophobic PDMS composite membranes for efficient ethanol recovery via pervaporation

Bio-ethanol, clean and renewable, has proved to be a promising alternative energy resource to replace conventional fossil fuels. In its continuous production via the fermentation–pervaporation process, hydrophobic polymer membranes such as polydimethylsiloxane (PDMS) have been developed to enrich ethanol from dilute fermentation broth. However, the efficiency of current ethanol recovery via pervaporation is not high enough for large-scale bioethanol production. To address this issue, we separately fabricated two types of lotus-inspired PDMS composite membranes to combine the beneficial properties (low surface energy and super-hydrophobicity) of superhydrophobic lotus leaves with the pervaporation process and optimized the separation performance. First, we prepared lotus leaf powder/PDMS mixed matrix membranes (MMMs) to exploit the intrinsic properties of lotus leaf’s material. In addition, polydivinylbenzene (PDVB)-coated PDMS composite membranes were fabricated to mimic and make use of the properties coming from the lotus leaf’s hierarchical structure. The morphology, surface chemistry, and pervaporation performance were systematically investigated for all the membranes. And results showed that MMMs at 1.5 wt% lotus powder loading displayed the ideal dispersion condition and increased the total flux of pervaporation process by 22% (750 g∙m−2∙h−1, 6 wt%, 37 °C). For the PDVB-coated PDMS membrane, the hierarchical roughness was successfully established on the PDMS surface, which resulted in a super-hydrophobic surface with water contact angle higher than 150°. As PDVB also has preferential adsorption for ethanol, the PDVB-coated PDMS membrane showed a higher ethanol recovery performance with the separation factor and total flux increased by 13% and 30%, respectively. Therefore, it was demonstrated that PDVB coating is an effective method to fabricate superhydrophobic membranes and both the two lotus-inspired strategies are feasible in optimizing pervaporation performance for ethanol recovery.

Effect of Graphite on The Pervaporation Performance of Silicone Rubber Membranes

Effect of Graphite on The Pervaporation Performance of Silicone Rubber Membranes

Tailoring the microstructure of poly(vinyl alcohol)-intercalated graphene oxide membranes for enhanced desalination performance of high-salinity water by pervaporation

Laminated graphene oxide (GO) membrane is promising in desalination owing to allowing unimpeded water permeation through the tunable interlayer nanochannels. To achieve highly efficient and stable desalination performance of GO membrane is crucial. Herein, GO membranes intercalated and cross-linked by poly(vinyl alcohol) (PVA) and supported on cellulose microfiltration membrane were fabricated via pressure-assisted filtration method for application in pervaporation desalination of high-salinity water. The interlayer spacing and microstructure of the GO membranes is successfully tailored by searching for appropriate intercalated PVA amount for cross-linking. The nanochannel microstructure was probed and its effect on the mass transport property of the membranes was revealed. The results show that the permeability of the GO-PVA membranes was dependent on both d-spacing and 3D cross-linking network between GO nanosheets. The optimized GO-PVA membranes displayed an outstanding water flux of over 98 kg/m2h and 99.99% salt rejection in desalinating 10 wt% NaCl solution at 85 °C. Benefiting from the formation of brick-mortar structure of GO layers with high adhesion strength provided by the cross-linked PVA chains with GO nanosheets, the membranes could toughly resist sonication destruction test and exhibited stable and reliable performance in pervaporation. The study helps understanding and optimizing the constitution of inner structure of intercalated GO membrane for efficient separation.

Novel fabrication of PSSAMA_Na capped silver nanoparticle embedded sodium alginate membranes for pervaporative dehydration of bioethanol.

Polystyrene-4-sulfonic acid co maleic acid sodium salt (PSSAMA_Na) capped silver nanoparticle (Ag_Np) embedded sodium alginate (Na-Alg) nanocomposite membranes have been developed to improve the pervaporation (PV) dehydration of bioethanol. The effect of PSSAMA_Na capped Ag_Nps on the micro-morphology, physicochemical properties and separation performance of the derived membranes was analyzed as a function of temperature at the azeotropic composition of the bioethanol–water mixture. WAXD analysis shows a decrease in crystalline domains with the increase in PSSAMA_Na capped Ag_Nps content and confirms the presence of Ag_Nps. DSC analysis demonstrated that the hydrophilic nature enhances as the PSSAMA_Na capped Ag_Nps content increases in the membrane matrix. Further, both total permeation flux and separation selectivity were increased with an increase in PSSAMA_Na capped Ag_Nps content. The results revealed that the membrane with 3 mass% of PSSAMA_Na capped Ag_Nps exhibited the highest permeation flux (13.40 × 10−2 kg m−2 h−1) and separation selectivity (11 406) at 30 °C which indicate its better PV performance. The total permeation flux and permeation flux of water values were close to each other, which confirms that the membranes can be efficiently used to remove the water from azeotropic aqueous bioethanol.