Modified MCM‐41 silica spheres filled polydimethylsiloxane membrane for dimethylcarbonate/methanol separation via pervaporation

Inorganic–organic hybrid membrane materials always exhibit high pervaporation performance for organic azeotropic mixtures. Here, MCM‐41 silica spheres were modified and embedded into polydimethylsiloxane, and a new filled membrane was obtained. The membrane was used in dimethylcarbonate (DMC) removal from DMC/methanol azeotropic mixture by pervaporation. The effect of membrane preparation parameters including modified MCM‐41 silica spheres loading, solvent concentration, and feed temperature on pervaporation properties was systematically studied. The results showed that separation factor and total flux of the filled membranes could be increased simultaneously. Additionally, the sorption and diffusion selectivity of the filled membranes were measured and discussed. The results demonstrated that diffusion selectivity was greatly enhanced by incorporating. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Sorption and pervaporation separation of ethyl tert—butyl ether and ethanol mixtures through a blended membrane

A new kind of membrane was prepared by blending poly(acrylic acid) with cellulose acetate propionate for the separation of ethyl tert—butyl ether and ethanol mixtures. The properties of the membranes were evaluated by the pervaporation separation of mixtures of ethyl tert—butyl ether/ethanol and the sorption experiments. The experimental results showed that the selectivity and the fluxes of this membrane depend on the blend composition and on that of processed feed mixtures. With respect to temperature, the ethanol fluxes obey the Arrhenius equation. The fluxes increase with the increase of the poly(acrylic acid) content in the blended membrane, the ethanol concentration in the feed, and the experimental temperature. But the selectivity decreases as the poly(acrylic acid) content and the experimental temperature are raised up. When the feed composition is varied, this membrane shows the special characteristics at the azeotropic composition. In the vicinity of the azeotropic point, the minimum values of ethanol concentration in the permeate and in sorption solution are obtained. The swelling ratios increase with an increase in the temperature and the ethanol concentration. The ethanol concentration in the sorption solution is also influenced by the temperature and composition of the mixtures. When the temperature increases, the sorption selectivity of the membrane decreases. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1631–1638, 1997     

Separation characteristics of pervaporation membrane separation processes using modified poly(vinyl alcohol) membranes

Modified poly(vinyl alcohol) (PVA) membranes prepared by the ‘solution technique’ were tested for ethanol-water mixtures by varying the reaction density (X_cr = 0.05, 0.1) at various temperatures. The results are compared with those of PVA membranes (X_cr = 0.05) prepared by the technique of the GFT Company, Germany.     

全硅沸石/聚二甲基硅氧烷渗透汽化膜制备及分离性能

考察了全硅沸石/聚二甲基硅氧烷(PDMS)渗透汽化均质膜制膜液中国液比(质量比)对渗透汽化膜性能的影响,利用均匀设计优化方法对交联时间、交联温度、全硅沸石填充鼍和PDMS中b胶量等对膜分离因子的影响进行了研究,制备了对丁醇分离性能较高的渗透汽化均质膜.50℃下,分离原料液质量分数为1.6%的丙酮-丁醇-乙醇-水溶液时,...     

Modified ZSM‐5/polydimethylsiloxane mixed matrix membranes for ethanol/water separation via pervaporation

In this article, chlorosilane‐modified ZSM‐5 particles were incorporated into polydimethylsiloxane (PDMS) to form mixed matrix membranes (MMMs) for ethanol/water mixture separation via pervaporation (PV). The membranes were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, and mechanical performance testing. The maximum loading and dispersion of ZSM‐5 into PDMS were improved by chlorosilane modification. To evaluate the PV performance, the MMMs were used to separate an aqueous ethanol solution. The effect of zeolite loading and operational conditions on PV performance was investigated in detail. The separation factor of the composite membranes filled with modified ZSM‐5 increased considerably versus unmodified membrane, while the total flux decreased to some degree. Of all the chlorosilane‐modified membranes, dodecyltrichlorosilane modified ZSM‐5 filled PDMS showed the best separation factor of 15.8 for ethanol. POLYM. COMPOS., 37:1282–1291, 2016. © 2014 Society of Plastics Engineers     

Pervaporation separation of water–isopropanol mixture using carboxymethylated poly(vinyl alcohol) composite membranes

The pervaporation separation of water–isopropanol mixtures was carried out using carboxymethylated poly(vinyl alcohol) (CMPVA) composite membranes. Carboxymethylated PVA (CMPVA) was synthesized by reacting PVA with various concentrations of monochloroacetic acid. Substitution efficiency of the CMPVA ranged from 12–32%. The cross‐sectional structure of the composite membrane for pervaporation was confirmed by scanning electron microscopy (SEM) exhibiting a 20‐μm active skin layer. Glass transition temperature of the CMPVA was in the range of 74–84°C, and decreased with increasing substitution efficiency. Degree of swelling and permeation flux for water–isopropanol in pervaporation increased with the substitution degree of carboxymethylation. CMPVA composite membrane, having 16% substitution efficiency, showed the following pervaporation performance; permeation flux of 831 g/m² h and separation factor of 362 measured at 80°C and 85 wt % feed isopropanol concentration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 241–249, 1999     

Pervaporation separation of water/alcohol mixtures through hydroxypropylated chitosan membranes

The present study investigated the pervaporation performance of novel hydroxypropylated chitosan (HPCS) membranes to separate water from an aqueous alcohol solution. Hydroxypropylated chitosan was prepared from the reaction of chitosan and propylene oxide. The results show that the separation factor decreases and the flux increases with increasing of the substitution degree of the hydroxypropylated chitosan membrane. Crosslinking with glutaraldehyde or treatment with Cu²⁺ can improve the pervaporation performance of modified chitosan membrane grately. The performance data indicate that the crosslinking hydroxypropylated chitosan membrane treated with Cu²⁺ is an excellent pervaporation membrane for the separation of alcohol–water mixtures, and one-stage separation is attainable for some alcohol–water mixtures such as an n-propanol–water and an isopropanol–water system, which has a good separation factor of 220 for the n-PrOH/water system and 240 for the i-PrOH/water system using 85 wt % alcohol concentration at 60°C. The flux for both cases is around 0.5 kg m⁻² h⁻¹. At the same time, the structure of the chemically modified chitosan membranes and their separation characteristics for aqueous alcohol solutions are also discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2035–2041, 1998     

Segmented network structures for the separation of water/ethanol mixtures by pervaporation

α,ω-Acrylate terminated poly(1,3-dioxolane) (polyDXL), was used as a hydrophilic cross-linker of hydrophobic poly(methyl methacrylate) (polyMMA) chains for the synthesis of amphiphilic AB-block copolymer networks. The application of these segmented networks as membranes for dehydration of water/ethanol mixtures by the pervaporation technique was investigated. Because the cross-links inhibit to a great extent phase separation between the components of these materials, as revealed by dynamic mechanical thermal analysis, an optimal control of the membrane characteristics could be achieved by variation of the hydrophilicity–hydrophobicity balance and the cross-link density. The combination of desorption experiments, determination of swelling degrees and calculation of deviation coefficients (ε) allowed us to demonstrate in these membranes the existence of a so-called coupling effect. It was shown that polyDXL plays a predominant role in the specific interactions between the membrane and the solvents, which cause the preferential water transport in all the membranes over the whole composition range of the feed mixture. © 1998 SCI.     

Pervaporation performance of polydimethylsiloxane membranes for separation of benzene/cyclohexane mixtures

Crosslinked polydimethylsiloxane/polyetherimide (PDMS/PEI) composite membranes were prepared, in which asymmetric microporous PEI membrane prepared with phase inversion method was acted as the microporous supporting layer in the flat‐plate composite membrane. The different function composition of the PDMS/PEI composite membranes were characterized by reflection Fourier transform infrared (FTIR) spectroscopy. The surface and section of PDMS/PEI composite membranes were investigated by scanning electron microscope (SEM). The composite membranes prepared in this work were employed in pervaporation separation of benzene/cyclohexane mixtures. Effects of feed temperature, feed composition, concentration of crosslinking agent on the separation efficiency of benzene/cyclohexane mixtures were investigated experimentally. In addition, the swelling rate and stableness of composite membrane during long time operation were studied, which should be significant for practical application. The results demonstrated that the pervaporation method could be very effective for separation of the benzene/cyclohexane mixtures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Kinetics of phase separation in polyurethane/polystyrene semi-1 interpenetrating polymer networks. 1. Light transmission studies

The phase separation of different in-situ semi-1 interpenetrating polymer networks (IPNs) based on polyurethane and polystyrene has been followed by light transmission. The effect of the presence ab initio of small amounts of homopolystyrene in the initial reaction mixture on the phase separation process has also been examined. If gelation of the polyurethane occurs before the onset of phase separation, the latter is impeded or strongly limited, and transparent semi-1 IPNs are obtained. In the opposite case, phase separation is macroscopic and the material is turbid.     

Cellulose–poly(acrylamide or acrylic acid) interpenetrating polymer network membranes for the pervaporation of water–ethanol mixtures

A new type of interpenetrating polymer network (IPN) pervaporation membranes based on cellulose and synthetic polymers was developed. They were prepared by free-radical polymerization of acrylamide or acrylic acid in the presence (or absence) of the crosslinking agent (allyldextran or N,N′-methylenebisacrylamide) within cellophane films swollen in the reaction mixture. The swelling behavior of these membranes in water–ethanol solutions and their separation characteristics were investigated depending on the polyacrylamide (PAAm) or poly(acrylic acid) (PAA) content in the IPN (C_p) and for ionic cellulose–PAA membranes depending on the degree of neutralization of carboxylic groups and on the type of counterions. IPN membranes were selective over a wide range of ethanol concentration in the feed. The separation factor (α) and the permeation rate (P) significantly improved with increasing C_p in IPN membranes, especially for the cellulose–PAA(K⁺ form) membranes (for 86% EtOH feed at 50°C, and α and P values reached 1500 and 1.6 kg/m² h, respectively). The results for ionic and nonionic IPN membranes were compared. The separation characteristics of membranes were in good correlation with their swelling behavior. The α values of the membranes depended on the affinity of the IPN polymer chains functional groups for water. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 761–769, 1998     

Sodium alginate–poly(hydroxyethylmethacrylate) interpenetrating polymeric network membranes for the pervaporation dehydration of ethanol and tetrahydrofuran

Interpenetrating polymeric network (IPN) membranes of sodium alginate (NaAlg) and various amounts of poly(hydroxyethylmethacrylate) (PHEMA) have been prepared and tested for the pervaporation dehydration of ethanol and tetrahydrofuran (THF). The presence of hydrophilic PHEMA in the IPN matrix was found to be responsible for increase in membrane selectivity to water. NaAlg–PHEMA IPN membrane containing 20 wt % of PHEMA exhibited a selectivity of 571 to water for the water–ethanol mixture and 857 for water–THF mixture. These data are much better than those observed for the pristine NaAlg membrane. However, flux of the IPN membranes was smaller than that of pristine NaAlg membrane. Comparatively higher flux values were observed for water–THF mixture than for water–ethanol mixture. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3324–3329, 2006     

Separation of alcohol–water mixture by pervaporation through a novel natural polymer blend membrane–chitosan/silk fibroin blend membrane

A novel natural polymer blend membrane, namely chitosan/silk fibroin blend membrane, was prepared. The selective solubility and the pervaporation properties of alcohol–water mixture were studied. The results showed that the membrane was water selective and the separation factor of ethanol–water mixture could be improved compared to pure chitosan membrane, when silk fibroin content in blend membrane was no more than 40 wt %. The blend membrane exhibited a best performance, (i.e., the water in permeate was large than 99 wt % when silk content was 20 wt % and the crosslinking agent–glutaraldehyde content was 0.5 mol %). The mechanism of improvement on pervaporation properties was explained by reducing the free volume and freeing hydrophilic groups of chitosan because of the strong intermolecular hydrogen bond forming between chitosan and silk fibroin in blend membrane. In addition, the influence of operation temperature and feed concentration as well as the pervaporation properties of isopropanol–water mixture were also studied. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 975–980, 1999     

TS‐1 molecular sieves filled polydimethylsiloxane membranes for ethanol/water separation via pervaporation

TS‐1 molecular sieves were synthesized and characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, and UV–Vis spectroscopy. Results showed that the morphology, crystallinity, and purity of TS‐1 were closely related to the Ti/Si ratio, crystallization time, crystallization temperature, and calcination time. The TS‐1 particles were incorporated into polydimethylsiloxane to form mixed matrix membranes (MMMs), and these MMMs were first used to separate ethanol/water mixtures via pervaporation. The MMMs with 50 wt% TS‐1 (Ti/Si ratio of 0.02) loading showed the highest separation factor of 14.1 for 5 wt% ethanol feed concentration at 50°C. POLYM. ENG. SCI., 56:583–589, 2016. © 2016 Society of Plastics Engineers     

Pervaporation separation of water–ethanol mixtures using metal‐ion‐exchanged poly(vinyl alcohol) (PVA)/sulfosuccinic acid (SSA) membranes

Poly(vinyl alcohol)/sulfosuccinic acid (PVA/SSA) membranes in the hydrogen form were converted to monovalent metal ion forms Li⁺, Na⁺, and K⁺. The effect of exchange with metal ions was investigated by measuring the swelling of water–ethanol (10/90) mixtures at 30 °C and by the pervaporative dehydration performance test for aqueous ethanol solutions with various ethanol concentrations at 30, 40, and 50 °C. In addition, electron spectroscopy for chemical analysis (ESCA) analysis was carried out to study the quantity of metal ions in membranes. From the ESCA analysis, the lithium ion quantity in the resulting membranes is greater than that of any other metal ions in question because of the easy diffusion of a smaller metal ion into the membrane matrix. The swelling ratio was in the following order: PVA/SSA‐Li⁺ > PVA/SSA‐Na⁺ > PVA/SSA‐K⁺ membranes. For pervaporation, the PVA/SSA‐Na⁺ membrane showed the lowest flux and highest separation factor for all aqueous ethanol solutions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1867–1873, 2002     

聚二甲基硅氧烷膜中乙醇-水的吸附和渗透蒸发行为

以乙醇/水体系为研究对象,结合F lory-Huggins理论,讨论溶胀过程的热力学行为,用以分析和考察聚二甲基硅氧烷(PDMS)膜在乙醇/水中的溶胀特性及组分间的耦合效应。结果表明,在乙醇质量分数20%—40%,膜的溶胀程度最大。渗透蒸发实验表明,水的渗透速率在乙醇质量分数不大于30%范围内变化很小,而乙醇的渗透速率基本随溶液中乙醇质量分数增加而增大。