Pervaporation Performance Research Articles

Enhanced pervaporation performance of SA-PFSA/ceramic hybrid membranes for ethanol dehydration

Abstract In this study, sodium alginate (SA)-perfluorinated sulfonic acid (PFSA)/ceramic hybrid membranes were successfully prepared by dip-coating method. The contorted rigid structure of PFSA immobilized the loose structure of SA as well as improved the interconnectivity so as to demonstrated high separation factors. Meanwhile, the ion clusters formed by SO3H groups of PFSA possessed high affinity for water, resulting in high water flux. The viscosity of blend solution, structures and properties of the hybrid membranes were investigated by viscometry, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), water contact angle meter and pervaporation dehydration. The effects of SA-PFSA ratio, PFSA content, feed composition and temperature on the separation performances of the hybrid membranes were investigated. The hybrid membrane fabricated by 2.0 wt% SA and 2.0 wt% PFSA demonstrated a high flux of 1155 g m−2 h−1 coupled with separation factor of 1149 by dehydration of 15 wt% water content ethanol-water mixture at 75 °C, reflecting superior pervaporation processing capacity.

Investigation on Performance of PDMS-Graphene/PES Hybrid Membrane for Pervaporative Separation of Phenol from Aqueous Streams

ABSTRACTThe pervaporative performances of pristine polydimethylsiloxane (PDMS) membrane and modified one by hybridizing with graphene nanosheets (PDMS-G) were evaluated for phenol removal from aqueous solutions. The incorporation of hydrophobic graphene nanosheets could enhance the process performance. The optimum performance was determined at 0.2 wt% crosslinker concentration and 0.2 wt% graphene content with a significant improvement in the separation factor up to 42.35. The enhanced separation factor can be attributed to optimized interfacial free volume in the structure of the membranes and formation of π-π interactions between graphene and phenol. The effects of operating parameters on separation performance were also evaluated.

Enhanced ethanol recovery of PDMS mixed matrix membranes with hydrophobically modified ZIF-90

In this study, dodecylamine-modified zeolitic imidazolate framework-90 (DLA-ZIF-90) particles with enhanced surface hydrophobicity are synthesized and incorporated into the polydimethylsiloxane (PDMS) matrix to fabricate novel PDMS/DLA-ZIF-90 mixed matrix membranes (MMMs) for ethanol recovery via pervaporation. The successful modification of ZIF-90 particles is investigated via various characterization techniques. The morphology and physicochemical properties of the PDMS/DLA-ZIF-90 MMMs are studied and characterized. Compared to the PDMS MMM with unmodified ZIF-90, PDMS/DLA-ZIF-90 MMM exhibits enhanced morphology homogeneity and separation performance, contributed by the flexible inner channels of ZIF-90-DLA particles with enhanced adsorption selectivity, as well as the improved affinity between ZIF-90-DLA particles and PDMS matrix. The MMM with 2.5 wt% DLA-ZIF-90 loading shows the best performance with the optimal flux of 99.5 g m−2 h−1 and corresponding separation factor of 15.1 at 60 °C. The effect of operation temperature is also studied. The performance benchmarking shows that PDMS/DLA-ZIF-90 MMM exhibits superior pervaporation performance to most other PDMS-based membranes, and may therefore shed valuable insights to the development of high-performance ZIF-based MMMs for organic recovery.

Vinyl Addition Copolymers of Norbornylnorbornene and Hydroxyhexafluoroisopropylnorbornene for Efficient Recovery of n-Butanol from Dilute Aqueous Solution via Pervaporation

The high energy cost to recover heavier alcohols, such as n-butanol, from dilute aqueous solution is a significant practical barrier to their large-scale bioproduction. Membrane pervaporation offers an energy-efficient alternative, provided membrane materials can be developed which provide both good alcohol selectivity and high flux. Previous work has revealed that vinyl addition polynorbornenes bearing substituents—especially hydroxyhexafluoroisopropyl—with an affinity for n-butanol have potential in this application, as their high glass transition temperature allows the formation of thin but mechanically robust selective layers in thin-film composite (TFC) membranes. In the present work, we synthesize both microphase-separated gradient copolymers, and homogeneous random copolymers, of hydroxyhexafluoroisopropylnorbornene (HFANB) with norbornylnorbornene (NBANB) and evaluate their n-butanol/water pervaporation performance. Compared with analogous copolymers of HFANB and n-butylnorbornene (BuNB), the grea...

Multilayer assembled CS-PSS/ceramic hollow fiber membranes for pervaporation dehydration

Abstract Pervaporation (PV) is an effective approach for the removal of trace or micro substances from solutions. PV membrane is considered to be the most essential element for this process. In this study, the fabrication of ceramic hollow fiber PV membranes is demonstrated through multilayer assembly of poly(4-styrenesulfonic acid) and chitosan. The surface and cross-section morphologies, physical and chemical structures as well as the hydrophilicity of the membranes were characterized by field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrophotometer (FTIR) and water contact angle, respectively. The PV performance of the composite membranes was investigated by dehydration of water-ethanol solution. The effect of assembly solution concentration on PV performance was studied systematically. The assembled composite membranes with the concentration of 0.75 wt% PSS solution exhibited the highest PV separation index (PSI) value of 4.47 × 105 with flux of 495 g/m2 h and separation factor of 904 for dehydration of 10 wt% water-ethanol solution at 70 °C.

Preparation of γ-methacryloxypropyl Trimethoxy Silane Cross-linked PDMS Membrane for Pervaporation Recovery of Butanol

The present study aimed to improve the pervaporation (PV) performances of polydimethylsiloxane (PDMS) membranes by using special cross-linkers. The γ-methacryloxypropyl trimethoxy silane (KH-570) cross-linked PDMS membranes were fabricated and characterized by FTIR, TGA, WCA, DSC, SEM, and swelling properties. Experimental results showed that the separation factor of the membrane increased slightly with the feed temperature whereas permeate flux increased. Butanol flux increased slowly with the feed concentration while the water flux decreased. The overall result indicated that the separation factor decreased slowly with the feed concentration. The membrane, with a thickness of 55 μm, showed a total flux of 308.4 g/m2h with a separation factor of 26.8 at 70 °C, and butanol permeability reached 11.13×105 Barrer with a membrane selectivity of 56.0.

Viscosity-driven in situ self-assembly strategy to fabricate cross-linked ZIF-90/PVA hybrid membranes for ethanol dehydration via pervaporation

Abstract In this study, poly(vinyl alcohol) (PVA) hybrid membranes with zeolitic imidazolate framework-90 (ZIF-90) particles were fabricated by the viscosity-driven in situ self-assembly of ZIF-90 particles in a PVA matrix and were employed for ethanol dehydration via pervaporation (PV) technology. By this method, the size-controlled and well-distributed ZIF-90 particles were successfully embedded into PVA membranes. Based on the cross-linking reactions between the ZIF-90 particles and the PVA matrix, the ZIF-90/PVA hybrid membranes demonstrated higher mechanical strength, swelling resistance, and a high separation performance for ethanol dehydration. The ZIF-90/PVA hybrid membranes were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, thermogravimetric analysis, a mechanical test, and water contact angle measurements. The effects of the ZIF-90 particle size, loading level, thermal treatment temperature, operation temperature, and the feed compositions of the PVA hybrid membranes on the PV performance were systematically explored. Accordingly, the hybrid membranes exhibited excellent water permeability and selectivity for water–ethanol mixture separation. Specifically, the ZIF-90/PVA hybrid membrane (M-8), which was treated thermally at 130 °C, exhibited its optimal PV performance at a flux of 268 g/(m2 h) and a separation factor of 1379 for the PV dehydration of the 90 wt% ethanol aqueous solution at 30 °C. The ZIF-90/PVA hybrid membranes exhibited excellent potential in the PV application for ethanol dehydration.

Effect of Si/Al ratio and amount of deposited MFI-type seed crystals on the separation performance of silicalite-1 membranes for ethanol/water mixtures in the presence of succinic acid

Silicalite-1 zeolite membranes were prepared on porous tubular α-Al2O3 supports by a secondary growth method. The influences of the Si/Al ratio and the amount of deposited MFI (silicalite-1 and ZSM-5) seed crystals on membrane pervaporation (PV) performance for the separation of ethanol/water (binary) and ethanol/water/succinic acid (ternary) mixtures were investigated. The prepared membranes were characterized by X-ray diffraction and scanning electron microscopy, and the Si and Al distributions in the membrane layers were determined by energy-dispersive X-ray line scanning. Each silicalite-1 membrane was composed of two layers: an MFI-seed-crystal layer that grew on the support surface, and another gel-derived silicalite-1 top layer that formed on the seed crystal layer. The texture of the MFI seed layer (i.e., the deposited amount and the Si/Al ratio) was found to play an important role in the separation process. When silicalite-1 seed crystals were used, the ethanol separation factor was high in the binary ethanol/water system, but lower in the presence of succinic acid. However, when ZSM-5 seeds were used, the ethanol separation factor in the ternary system improved. These results suggest that silicalite-1 membranes prepared using ZSM-5 seed crystals are effective for the recovery of ethanol in the presence of organic acids.

Lampung natural zeolite filled cellulose acetate membrane for pervaporation of ethanol-water mixtures

Pervaporation of ethanol–water can be cost-competitive in the production of renewable biomass ethanol. For the purpose of improving the pervaporation performance of polymeric membranes, we prepared cellulose acetate (CA) filled Lampung Natural Zeolite (LNZ) membranes by incorporating LNZ into CA for pervaporation separation of ethanol-water mixtures. The characteristics and performance of these filled membranes in the varied ratio of CA:LNZ (30:0, 30:5, 30:10, 30: 20, 20:20 and 40:10) wt% were investigated. The prepared membranes were characterized for pervaporation membrane performance such as %water content and membrane swelling degree. Further, the permeation flux and selectivity of membrane were also observed. The results of investigation show that water content of membrane tends to increase with increase of LNZ content. However, the swelling degree of membrane decrease compared than that of CA control membrane. The permeation flux and the selectivity of membranes tend to increase continuously. The CA membrane with ratio of CA:LNZ 30:20 shows the highest selectivity of 80.42 with a permeation flux of 0.986 kg/(m2 h) and ethanol concentration of 99.08 wt%.

A water-based mixing process for fabricating ZIF-8/PEG mixed matrix membranes with efficient desulfurization performance

In this article, ZIF-8 nanoparticles were synthesized in water and directly added to a polyethyleneglycol (PEG) aqueous solution (water-based mixing process) to prepare ZIF-8/PEG mixed matrix membranes (MMMs) for pervaporation desulfurization. The structure and properties of ZIF-8 particles were characterized by Fourier Transform-Infrared Spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and BET analysis. The surface composition and structural morphology of all ZIF-8/PEG MMMs were systematically investigated by FT-IR and SEM. The effect of ZIF-8 content on the pervaporation performance of ZIF-8/PEG membranes was investigated. Versus pure PEG membranes, both the total flux and the sulfur enrichment factor of the ZIF-8/PEG MMMs were remarkably increased. This phenomenon is attributed to the good compatibility between PEG and ZIF-8 particles and the high thiophene selective sorption of ZIF-8 particles (confirmed by molecular simulation). Optimal pervaporation performance was achieved at a 4 wt% loading of ZIF-8 particles with the flux of 1.96 kg/(m2 h) and the sulfur enrichment factor of 8.93. These increased by 397.46% and 18.75% versus pristine PEG membrane, respectively. In addition, the effect of operation temperature and feed sulfur content on membrane performance were also systematically investigated.

Seeding-free synthesis of oriented zeolite LTA membrane on PDI-modified support for dehydration of alcohols

ABSTRACTA seeding-free synthesis method is developed for preparation of oriented zeolite LTA membranes by using 1,4-phenylene diisocyanate (PDI) as a molecular linker. Before hydrothermal synthesis, –NCO groups are introduced with the functionalization of Al2O3 supports by PDI. A thin, well intergrown zeolite LTA membrane with a thickness of about 4.0 µm can be formed on the PDI-modified Al2O3 supports. The zeolite LTA membrane displays high pervaporation performances for dehydration of alcohols. At 90°C, the separation factor of the zeolite LTA membrane is 4480 for dehydration of 95 wt% ethanol/water mixtures, with a high water flux of 3.4 kg·m−2·h−1.

Pervaporation performance of crosslinked PVA membranes in the vicinity of the glass transition temperature

This work investigates the pervaporation performance of crosslinked poly (vinyl alcohol) (PVA) membranes for ethanol dehydration near the glass transition. The solubility of water and ethanol mixture in the membranes was measured as a function of feed composition and sorption temperature, and the data was modelled by perturbed-chain statistical associating fluid theory (PC-SAFT). Importantly, this approach allows the solubility of the two components to be determined individually. Model results show that the heat of sorption of water and ethanol was constant across the temperature range. Water permeance generally decreased when operational temperature increased, indicating a solubility-controlled transport behavior. The permeance also increased when water feed concentration increased. Activation energy analysis provided more insights about the influence of membrane properties on the mass transport mechanism. At 90 wt% ethanol feed composition, the apparent activation energy (Ea) for water permeation changed from 9.6 kJ mol−1 when temperature was < 70 °C to − 9.1 kJ mol−1 when temperature was > 80 °C. When the feed composition decreased to 80 wt% ethanol, a transition was observed at a lower temperature range (60–65 °C). These changes were related to changes in the activation energy of diffusion, given the heat of sorption was constant. The permeability of ethanol was lower due to its larger molecular size, but a similar transition was observed for the 80 wt% ethanol case.

Preparation and characterization of SiO2/PDMS/PVDF composite membrane for phenols recovery from coal gasification wastewater in pervaporation

Silica (SiO2)/polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) composite membranes were prepared through a dynamic negative pressure method for phenols recovery from coal gasification wastewater (CGW) in pervaporation process. Multiple techniques including scanning electron microscopy (SEM), water contact angle (WCA) and fourier transform adsorption spectrum (FTIR) were used to examine the surface morphology, hydrophobic properties and functional groups of the modified PVDF hollow fiber membranes, respectively. The effects of SiO2 concentration, coating time and coating pressure on pervaporation performance were systematically studied. The operating conditions obtained are as follows: 12wt.% SiO2, coating time 60min, coating pressure 50kPa. Under the optimum conditions, the phenols flux and separation factor were obtained as 6.55gm−2h−1 and 2.59, respectively. Results show that separation factor in pervaporation process based on 12wt.% SiO2 filled PDMS/PVDF composite membranes was about 2.5 times higher than that of the PDMS/PVDF membrane.

Preparation of high‐performance zeolite NaA membranes in clear solution by adding SiO2 into Al2O3 hollow‐fiber precursor

Zeolite NaA membranes were prepared in a clear synthesis solution without the aid of nanoseeds. To improve the properties of the membranes formed in a clear solution, alumina hollow fibers were fabricated by adding silica powder to the conventional spinning slurry, resulting in hollow fibers with a mullite phase. Prior to the membrane synthesis, the hollow fibers were pretreated by dipping in an aged synthesis solution diluted with isopropanol. Dense zeolite NaA membranes on mullite‐containing alumina hollow fibers were successfully obtained at 100°C for 2 h without the aid of nanoseeds. The membranes have a good pervaporation performance with a high flux of 10.8 kg m−2 h−1 and a separation factor of over 10,000. The abundant mullite‐phase hydroxyl groups on the support surface promote the nucleation and growth of zeolite crystals on the support, resulting in dense membranes. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2679–2688, 2018

Experimental and modelling studies of pervaporative removal of odorous diacetyl and S-methylthiobutanoate from aqueous solutions using PEBA membrane

Abstract This work focuses on the recovery of two odorous compounds (diacetyl and S-methylthiobutanoate) from dilute aqueous solutions by pervaporation using polyether block amide 2533 (PEBA) membrane. The pervaporation process was experimentally investigated combined with model simulation. The PEBA 2533 membrane was prepared by solvent casting method, and effect of temperature and concentration on its flux and permselectivity were studied through pervaporation experiments using binary model solutions. A correlation between experimental results and those obtained via numerical model as function of feed temperature and concentration using solution-diffusion theory describing flux and separation factor was established. The sorption properties of PEBA in the organic aqueous solution were predicted by the Flory-Huggins model and the interaction parameters were obtained from the Hansen solubility parameter method using group contribution method. A semi-empirical relationship of the diffusion coefficient for binary mixture through PEBA membrane was proposed as a function of concentration and temperature, which was validated by comparison with experimental data. The results showed that at a given temperature, the organic flux increased with increasing feed concentration while the separation factors decreased for the both the mixtures, while elevated temperature increased the total flux without sacrificing the separation factor. The maximum organic flux and separation factors for diacetyl/water and S-methylthiobutanoate/water mixtures, were 1.6 g·m−2·h−1 and 40, and 4.6 g·m−2·h−1 and 110, respectively. The pervaporation performance for the binary mixtures system was believed to be dependent on diffusion process where PEBA membrane exhibited appreciable selectivity to S-methylthiobutanoate at low concentrations. The present approach based on the prediction of data using Flory-Huggins model and experimental results for the separation and extraction of S-methylthiobutanoate and diacetyl from aqueous solution could be of great help on industrial level applications and process designing.

Preparation of polyamide/polyacrylonitrile composite hollow fiber membrane by synchronous procedure of spinning and interfacial polymerization

In this investigation, a new concept for fabrication polyamide (PA)/polyacrylonitrile (PAN) composite hollow fiber membrane by using a triple orifice spinneret was explored. Tetraethylenepentamine (TEPA) and trimesoyl chloride (TMC) were used as the monomers of aqueous solution and acid chloride solution, respectively. The PAN dope, TEPA solution and TMC solution were pumped into the outermost, middle and inner channel of the triple orifice spinneret, respectively, and then co-extruded into water from the outlet of the spinneret simultaneously. The PA layer then was formed on the lumen surface of the synchronous wet-spun PAN hollow fiber membrane. SiO2 was added into the dope to increase the hydrophilicity of the dope. The resultant PA/PAN composite hollow fibers were characterized by using FTIR-ATR, SEM, light transmission, contact angle and positron annihilation spectroscopy (PAS). The effects of SiO2 content, TEPA concentration, as well as the TEPA solution flow rate on the properties and pervaporation performances of resultant PA/PAN composite hollow fibers were investigated. The PA layer was completely attached to the lumen surface of the resulted hollow fibers through the spinning and interfacial polymerization synchronous procedure. The pervaporation performances with 419 g/m2h of permeation flux and 96.6 wt% of water content in permeate of the 90 wt% aqueous isopropanol solution at 25 °C can be obtained through the synchronous fabricated PA/PAN composite hollow fiber membrane which was fabricated by the 18 wt% PAN dope containing 5 wt% SiO2, 1 ml/min of 14 wt% TEPA solution and 2 ml/min of 1 wt% TMC solution.

Matrimid®5218 dense membrane for the separation of azeotropic MeOH-MTBE mixtures by pervaporation

Matrimid®5218 dense membranes were produced using NMP by solvent evaporation. The membranes have been used, for the first time, in pervaporation (PV) separation of azeotropic methanol (MeOH)- methyl tert-butyl ether (MTBE) mixtures (14.3 and 85.7 wt%, respectively). The membranes were characterized by TGA, SEM, DSC, contact angle and swelling tests. The PV experiments were carried out at different feed temperatures (25–45 °C) and vacuum pressures (0.0538, 0.2400, 2.1000 mbar). Moreover, an analysis of the PV process through the Arrhenius relationship has been provided. The feed temperature (in the range of 25–45 °C) affected mainly the MeOH permeation producing an increasing on its partial permeate flux and separation factor as well. Indeed, the best performances of Matrimid® were found at 45 °C and 0.054 mbar, where a permeate flux and a separation factor of about 0.073 kg m−2 h−1 and 21.16, respectively, were obtained. Finally, the Matrimid PV performance was compared with other polymeric membranes at the azeotropic conditions.

Properties and pervaporation performance of poly(vinyl alcohol) membranes crosslinked with various dianhydrides

ABSTRACTIn this work, three dianhydrides with similar chemical structures, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), 4,4′‐oxydiphthalic anhydride (ODPA), and pyromellitic dianhydride (PMDA), are employed for the crosslinking modification of poly(vinyl alcohol) (PVA) membranes for ethanol dehydration via pervaporation. The changes in crosslinking degree, surface hydrophilicity, and glass‐transition temperature are investigated and compared. Compared to the pure PVA membrane, all crosslinked membranes show higher fluxes but lower separation factors, because of the higher fractional free volume and the lower hydrophilicity by the crosslinking of the PVA matrix, respectively. In addition, all crosslinked PVA membranes exhibit similar flux, and the separation factor presents a decreasing order of PVA/PMDA‐2 &gt; PVA/ODPA‐2 &gt; PVA/BTDA‐2, which is in the reverse order of their hydrophilicity, probably because of the reduction in the swelling resistance. With the PMDA content increasing from 0.01 to 0.04 mol/(kg PVA) in the PVA/PMDA crosslinked membranes, the crosslinking degree is enhanced and the hydrogen bonding is weakened, resulting in a flux increase from 120.2 to 190.8 g m−2 h−1, but the separation factor declines from 306 to 58. This work is believed to provide useful insight on the chemical modification of PVA membranes for pervaporation and other membrane‐based separation applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46159.

The effect of bioadhesive on the interfacial compatibility and pervaporation performance of composite membranes by MD and GCMC simulation

Combing molecular dynamics (MD) and Grand Canonical Monte Carlo (GCMC) simulation, the effect of bioadhesive transition layer on the interfacial compatibility of the pervaporation composite membranes, and the pervaporation performance toward penetrant molecules were investigated. In our previous experimental study, the structural stability and permeability selectivity of the composite membranes were considerably enhanced by the introduction of bioadhesive carbopol (CP). In the present study, the interfacial compatibility and the interfacial energies between the chitosan (CS) separation layer, CP transition layer and the support layer were investigated, respectively. The mobility of polymer chains, free volume in bulk and interface regions were evaluated by the mean-square displacement (MSD) and free volume voids (FFV) analysis. The diffusion and sorption behavior of water/ethanol molecules in bulk and interface regions were characterized. The simulation results of membrane structure have good consistency, indicating that the introduction of CP transition layer improved the interfacial compatibility and interaction between the separation layer and the support layer. Comparing the bulk region of the separation layer, the mobility and free volume of the polymer chain in the interface region decreased and thus reduced the swelling of CS active layer, revealing the increased diffusion selectivity toward the permeated water and ethanol molecules. The strong hydrogen bonds interaction between the COOH of the CP transition layer and water molecules increased the adsorption of water molecules in the interface region. The simulation results were quite consistent with the experimental results.

Fabrication of Solvent‐Resistant Copolyimide Membranes for Pervaporation Recovery of Amide Solvents

AbstractDimethylformamide and dimethylacetamide are important industrial chemicals, which are used, e.g., as solvents in the manufacturing of polyurethane products. They are conventionally recovered by distillation associated with high energy consumption and operating costs. In contrast, pervaporation is an energy‐efficient membrane separation method. Ceramic‐supported copolyimide membranes were synthesized via the two‐step thermal imidization method and applied to pervaporation recovery of dimethylformamide and dimethylacetamide. The prepared membrane demonstrated high resistance to the two amides in a wide concentration range. Effects of operating parameters such as feed temperature and feed concentration on pervaporation performances were investigated. The results showed that the copolyimide membrane is a promising candidate for the recovery of high concentrations of amide solvents.