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1.
The present work considers the application of an integrated pervaporation process to improve the pervaporation performance of acetic acid over water. This integrated pervaporation process was based on a plain PDMS membrane with a hydrophobic ionic liquid composed of a heterocyclic cation and [PF6]- anions. The hydrophobic ionic liquid was introduced as the third phase between the aqueous phase and the plain PDMS membrane for improving mass-transfer of acetic acid from its aqueous matrix to the PDMS membrane. The primary results indicated that the ionic liquid as an extractant prior to pervaporation was favorable for improving the permeate selectivity and the permeate flux of acetic acid compared with using only a plain PDMS membrane. This performance could be attributed to the acetic acid concentrated and the water molecules rejected by ionic liquid prior to pervaporation. Extraction of a real effluent containing acetic acid from an antibiotic pharmaceutical plant was carried out using the above integrated pervaporation, and the results imply that this integrated pervaporation process could be scaled up for recovering acetic acids over its water-rich effluents. 相似文献
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In this study, a hybrid hydrophobic/hydrophilic pervaporation process was employed to separate and purify isobutanol from its dilute aqueous solutions. For this purpose, composite polydimethylsiloxane membranes were initially used for the recovery of isobutanol by hydrophobic pervaporation. Then the hydrophilic pervaporation with a composite polyvinyl alcohol membrane was utilized to separate water from the organic phase of the permeate stream of the hydrophobic pervaporation. The effect of feed flow rate on the performance of pervaporation was investigated. The resistance in series model was also applied to calculate the transport resistances through the composite membranes. It was observed that an enhancement in the feed flow rate led to higher permeation flux and selectivity of the more permeable component, while the flux of the less permeable component was almost constant. Also, the ratio of liquid boundary layer resistance to membrane layer resistance decreased by an increase in the feed flow rate. The isobutanol with a purity of higher than 99 wt.% was produced by the hybrid hydrophobic/hydrophilic pervaporation technique from a 2 wt.% aqueous isobutanol solution. 相似文献
4.
《分离科学与技术》2012,47(12):2894-2914
Abstract In order to simultaneously achieve both high permselectivity and permeability (flux) for the recovery of aromatic compounds such as phenol from aqueous streams, a composite organophilic hollow fiber based pervaporation process using PDMS/PEBA as two-layer membranes has been developed. The process employed a hydrophobic microporous polypropylene hollow fiber, having thin layers of silicones (PDMS) and PEBA polymers coating on the inside diameter. The composite membrane module is used to investigate the pervaporation behavior of phenol in water in a separate study; and that of a mixture of phenol, methanol, and formaldehyde in an aqueous stream (a typical constituent of wastewater stream of phenol-formaldehyde resin manufacturing process) in another study. The fluxes of phenol and water increase relatively linearly with increasing concentration especially at low feed concentration, and exhibit a near plateau with further increase in concentration. As a result, the phenol/water separation factor decreases as the feed concentration increases. Significant improvement in phenol/water separation factor and phenol flux is achieved for this two-layer (PDMS/PEBA) membranes as compared to that achieved using only PDMS membrane. The phenol and water fluxes and the separation factor are highly sensitive to permeate pressure as all decrease sharply with increase in permeate pressure. For this membrane, an increase in temperature increases the separation factor, and also permeation fluxes of phenol and water. An increase in feed-solution velocity does not have a significant effect on phenol and water fluxes, and also on the separation factor at least within the range of the feed-solution velocity considered. In the study of pervaporation behavior of a typical constituent of wastewater stream of phenol-formaldehyde resin manufacturing process, phenol permeation shows a much higher flux and a higher increase in flux with increase in concentration is also exhibited as compared to that exhibited by methanol permeation. This thus indicates that the membrane is more permeable to phenol than to methanol and formaldehyde. 相似文献
5.
From the reference[1] it is known that the addition of silicalite-1 in silicone rubber membranes results in an increase of both flux and selectivity for alcohol in the separation of alcohol/water by pervaporation.In order to enhance performance of pervaporation toward the aqueous solution of acetic acid,incorporation of carbon molecular sieve(CMS)into a PDMS membrane was investigated. CMS is widely used in adsorption processes because of its high selectivity toward certain compounds[2]. It was assumed that the flux and selectivity of pure PDMS membrane could be enhanced owing to the preferential adsorption of CMS to organics.CMS content in the membrane and several important pervaporation operation parameters, including feed concentration of acetic acid, and feed temperature, were investigated. 相似文献
6.
Using a pervaporation process, a surface-modified hydrophobic membrane was used for recovery of esters which are volatile
organic flavor compounds; ethyl acetate (EA), propyl acetate (PA), and butyl acetate (BA). A surface-modified tube-type membrane
was used to evaluate the effects of the feed concentration (0.15–0.60 wt%) and feed temperature (30–50 °C) on the separation
of EA, PA, and BA from dilute aqueous solutions. The permeation flux increased with the increasing feed ester concentration
and operating temperature. EA, PA, and BA in the permeate were concentrated up to 9.13–32.26, 11.44–34.95, and 14.96–36.37
wt%, respectively. The enrichment factors for the 0.15–0.60 wt% feed solution of EA and BA were in the range of 48.5-62.8
and 97.7-101.5, respectively. Phase separation occurred in the permeate stream because the ester concentration in the permeate
was above the saturation limit. This meant that selectivity of the membrane was high enough for the recovery of esters from
dilute aqueous solution, even though the enrichment factor of the membrane was lower than that of non-porous PDMS membrane.
The fluxes of EA, PA, and BA at 0.60 wt% (6,000 ppm) feed concentration and 40 °C were 254, 296, and 318 g/m2.hr, which are much higher than those obtained with polymer membranes. In the case of non-porous PDMS at feed concentrations
of 90-4,800 ppm and at 45 °C, it was reported that the permeate flux of EA was 1.1–5.8 g/m2.h. Compared to non-porous PDMS, the surface-modified membrane investigated in this study showed a much higher flux and enough
selectivity of esters. 相似文献
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为探究出适合分离水中的乙酸正丁酯和乙酸乙酯的新型渗透汽化膜材料,选用沸石ZSM-5 对聚二甲基硅氧烷(PDMS)材料进行填充改性,以聚偏氟乙烯(PVDF)为支撑层,采用刮涂法制备PDMS/ZSM-5/PVDF复合膜渗透汽化分离水中的乙酸正丁酯和乙酸乙酯。采用SEM、接触角测量仪、FTIR、TGA和XRD等对膜材料物理化学性能进行表征,考察了膜材料的溶胀行为及渗透汽化性能。结果表明,ZSM-5在 PDMS 膜中分散均匀,且没有发生化学作用,并提高了膜材料的疏水性和热稳定性。随着ZSM-5添加量的增加,膜在乙酸正丁酯和乙酸乙酯的溶胀度和待分离组分在膜材料中的扩散速率不断增加。随着进料浓度和温度的增加,渗透通量不断增大,分离因子先增大后减小。随着ZSM-5在PDMS/ZSM-5/PVDF复合膜中含量的增加,总渗透通量增加,而分离因子呈现先增加后减小的趋势。当添加量为10%(质量)时,分离因子达到最大值。对于乙酸正丁酯/水体系,渗透通量和分离因子最大值分别为319 g·m -2·h -1和131;而对于乙酸乙酯/水体系,渗透通量和分离因子最大值分别为1385 g·m -2·h -1和121。 相似文献
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Ngoc Lan Mai Sung Hoon Kim Sung Ho Ha Hwa Sung Shin Yoon-Mo Koo 《Korean Journal of Chemical Engineering》2013,30(9):1804-1809
An effective in situ recovery of acetone, butanol and ethanol (ABE) from fermentation broth is requisite to overcome the low productivity of ABE production. Pervaporation has proven to be one of the best methods for recovering ABE from fermentation broth. We fabricated an immobilized ionic liquid-polydimethylsiloxane (PDMS) membrane in which a [Tf2N]? based ionic liquid covalently bound to the PDMS backbone polymer and used it to recover ABE from aqueous solution by pervaporation. Permeate flux of immobilized IL-PDMS membrane was 7.8 times higher than that of conventional supported IL-PDMS membrane (where ILs are physically absorbed on the supported membrane). Butanol enrichment factor of immobilized IL-PDMS membrane was three-times higher than that of PDMS membrane. In addition, high enrichment factor both to acetone and ethanol as well as high operational stability of immobilized IL-PDMS membrane can enhance the efficacy of ABE recovery by employing this membrane. 相似文献
10.
《分离科学与技术》2012,47(7):843-861
Abstract Several organophilic membranes were utilized to selectively permeate ethanol, n-butanol, and t-butanol from dilute aqueous mixtures using pervaporation (PV). Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes were utilized to investigate the effect of temperature, pressure, and start-up/transient time on the separation of aqueous ethanol mixtures. Results indicate optimal ethanol selectivity and flux at the lowest permeate-side pressure. Increased temperature significantly enhanced the productivity of PTMSP, but extended operation of the PTMSP membranes at high temperatures resulted in flux degradation. Two other hydrophobic membranes, poly(dimethyl siloxane) (PDMS) and a poly(methoxy siloxane) (PMS) composite, were used to separate n-butanol and t-butanol from dilute aqueous mixtures. The effect of feed concentration on the flux and selectivity was investigated. Both membranes were found to be more permeable to n-butanol than t-butanol. The PDMS membrane was found to be more effective than the PMS membrane in terms of flux and selectivity. The effect of membrane thickness on water permeation and on organic selectivity was also studied using the PDMS membrane. 相似文献
11.
Choong-Kyun Yeom James M. Dickson Michael A. Brook 《Korean Journal of Chemical Engineering》1996,13(5):482-488
A new silicone pervaporation membrane for the removal of one of trace organies, 1,2-dichloroethane from water has been developed
using polydimethylsiloxane (PDMS) and oligomeric silylstyrene as a crosslinking agent of PDMS. Optimal conditions for fabricating
the best membrane were determined from swelling measurements ard pervaporation experiments and then the membrane was characterized
at different membrane thickness and operating conditions. In the pervaporation separation of 55–70 ppm of l,2-dichlorocthanc
aqueous mixtures, the developed membrane has flux of 2.5–330 g/(m2.h) and selectivity of 230–1750 depending on membrane thickness, permeate pressure and operating Temperature. Water permeation
through thin membrane was found to be subjected to significant desorption resistance, while the desorption resistance and
thermodynamic factors as well as the concentration polarization of the organic at the boundary layer in feed can affect the
organic permeation, depending on membrane thickness. Selectivity change with permcaic pressure depends on membrane thickness:
at small membrane thickness range, selectivity increases with permeate pressure and at large thickness region it decreases.
From the Arrhenius plots of each component fluxes, the permeation activation energies were determined. Through an analysis
of the permeation activation energies of each components, the desorption resistance as well as the effects of the thermodynamic
factors on permeation was qualitatively characterized. 相似文献
12.
Surface-modified alumina membrane (A12O3) was used for ester flavor recovery by pervaporation. This study focused on the permeation characteristics of ester compounds
(ethyl acetate, EA; ethyl propionate, EP; ethyl butyrate, EB) through tube-type hydrophobic membrane. Experiments were performed
to evaluate the effects of the feed concentration (0.15-0.60 wt%) and temperature (30-50 ‡C) on separation of EA, EP, and
EB from aqueous solutions. It was found that the permeation flux increased with increasing feed ester concentration and operating
temperature. The fluxes of EA, EP, and EB at 0.60wt% feed concentration and 40 ‡C were 254, 343, and 377 g/m2 hr, which was much higher than those of polymer membranes. It was reported that the permeate flux of EA with PDMS was 1.1-58
g/m2Phr at feed concentration of 90-4,800 ppm and 45 ‡C. The separation factors for the 0.15-0.60 wt% feed solution of EA, EP,
and EB at 40 ‡C were in the range of 66.9-78.9, 106.5-97.3, and 120.5-122.8, respectively. Due to the high separation factor,
phase separation occurred in permeate stream because the ester concentration in permeate was much above the saturation limit. 相似文献
13.
In this work, free volume theories are coupled with a thermodynamic model and generalized Fick's law to develop a mass transfer model based on solution‐diffusion mechanism for pervaporation process with a hydrophobic polymeric membrane. The Wesselingh, Fujita and Vrentas‐Duda's theories are used to calculate concentration‐dependent diffusion coefficient of permeants inside polydimethylsiloxane membrane. The sorption and pervaporation experiments on aqueous ethanol solutions are performed to validate the sorption and pervaporation models. The results reveal that the proposed models are able to predict influences of feed concentration and temperature as well as permeate‐side pressure on partial fluxes through the membrane. The comparative investigation indicated that Wesselingh's free volume theory underestimated the diffusion coefficients inside the membrane and the accuracy of the model used this theory is very low for prediction of the permeation flux. Generally, Fujita and Vrentas‐Duda's theories are found to be much more accurate especially for dilute aqueous feed solutions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40581. 相似文献
14.
《分离科学与技术》2012,47(13-14):2167-2178
Abstract A pervaporation apparatus was designed and tested in an effort to develop an integrated fermentation and product recovery process for acetone-butanol-ethanol (ABE) fermentation. A crossflow membrane module able to accommodate flat sheet hydrophobic membranes was used for the experiments. Permeate vapors were collected under vacuum and condensed in a dry ice/ethanol cold trap. The apparatus containing polytetrafluoroethylene membranes was tested using butanol-water and model solutions of ABE products. Parameters such as product concentration, component effect, temperature, and permeate side pressure were examined. 相似文献
15.
Steady microfluidic measurements of mutual diffusion coefficients of liquid binary mixtures
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Anne Bouchaudy Charles Loussert Jean‐Baptiste Salmon 《American Institute of Chemical Engineers》2018,64(1):358-366
We present a microfluidic method leading to accurate measurements of the mutual diffusion coefficient of a liquid binary mixture over the whole solute concentration range in a single experiment. This method fully exploits solvent pervaporation through a poly(dimethylsiloxane) (PDMS) membrane to obtain a steady concentration gradient within a microfluidic channel. Our method is applicable for solutes which cannot permeate through PDMS, and requires the activity and the density over the full concentration range as input parameters. We demonstrate the accuracy of our methodology by measuring the mutual diffusion coefficient of the water (1) + glycerol (2) mixture, from measurements of the concentration gradient using Raman confocal spectroscopy and the pervaporation‐induced flow using particle tracking velocimetry. © 2017 American Institute of Chemical Engineers AIChE J, 63: 358–366, 2018 相似文献
16.
Pervaporation membrane with preferential permeation for organic compounds over water was prepared and characterized. Selection of membrane material and the effects of polydimethylsiloxane (PDMS), cross-linker, and catalyst concentrations on performances of pervaporation membrane at room temperature were discussed. In addition, the time of cross-linking, and the kinds of basic plate in the process of preparation were tested. The formulation of pervaporation membrane material was determined. Through the characterization of membrane by infrared spectrometry(IR), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD), it is proved that the structures and characters are suitable for the pervaporation process. Experiments also demonstrate that the permeate flux and separation factor are suitable for the process. 相似文献
17.
A polydimethylsiloxane (PDMS) membrane was improved by graft polymerization of 1H,1H,9H-hexadecafluorononyl methacrylate (HDFNMA) by plasma, which had the effect of increasing the selectivity for volatile organic compounds (VOCs). The use of an easy quantitative analysis for the pervaporation through plasma-grafted PDMS membranes was investigated. The degrees of grafting on the inside and reverse side of the grafted PDMS membranes were lower than on the surface. Only part of the HDFNMA sorbed into the PDMS membrane was grafted onto the PDMS membrane. The relationship between the feed concentration and the permeate concentration was observed to be linear. The pervaporation through the grafted PDMS membrane could be used for easy quantitative analysis. The solubility of VOCs for the grafted PDMS membrane was high when compared with the solubility for the PDMS membrane. The grafted PDMS membrane that had high VOC concentrations of the sorbed solution showed an excellent separation performance. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1835–1844, 1999 相似文献
18.
Since pervaporation process is the coupling of solution and diffusion mechanisms, a sorption study was carried out with membranes prepared by cross-linking polyvinylalcohol (PVA) and polidimethylsiloxane (PDMS). Tartaric acid (Tac) was used as the cross-linking agent for PVA, and a commercial cross-linking agent was used for PDMS. Sorption experiments were carried out at 30-50°C temperature range in pure water and ethyl acetate using the films prepared. The PVA and PDMS films prepared preferentially sorb water and ethylacetate, respectively. A pervaporation study at 30°C was carried out for pure ethylacetate and pure water, and mixtures of ethylacetate containing 2 and 2.5 wt% water using 100 μm thick PVA membrane. The results indicate that the PVA membrane prepared is extremely selective for water. 相似文献
19.
The mass transport of components during the pervaporation of binary butanol aqueous solutions using commercial PDMS membranes has been investigated. A simplified approach of the Maxwell–Stefan model was extended to include the effect of membrane swelling and temperature on the diffusion coefficients and sorption properties. Partial permeate fluxes obtained at different temperatures and concentrations have been fitted to determine the extended model parameters. The sorption properties and diffusion coefficients of components have been estimated using fitted parameters. Predicted values of the solubility and diffusivity were used to calculate and compare the permeability of the components under different operating conditions.
Abbreviations: HPLC - High performance liquid chromatography; MS - Maxwell–Stefan; PDMS - Polydimethylsiloxane; SEM - Scanning electron microscope 相似文献
20.
将碳纳米管(CNTs)填充到PDMS中制备出CNTs/PDMS杂化膜,并将其用于乙醇/水体系的分离,发现由多壁碳纳米管制备的膜分离性能优于单壁碳纳米管填充膜,在40℃下,进料乙醇浓度为5%(质量分数)时,膜的分离因子可由8.3提高到10.0,渗透通量为206.2 g·(m2·h)-1;采用十二烷基三氯硅烷对多壁碳纳米管进行修饰,并对修饰前后碳纳米管的性能进行表征,研究表明修饰后碳纳米管表面形成疏水层,碳纳米管的疏水性增强;将修饰后的碳纳米管填充到PDMS中,可进一步提高杂化膜对乙醇的选择性,膜的分离因子可提高到11.3,渗透通量为130.9 g·(m2·h)-1。 相似文献