Perfluorosulfonic acid—Tetraethoxysilane/polyacrylonitrile (PFSA‐TEOS/PAN) hollow fiber composite membranes prepared for pervaporation dehydration of ethyl acetate–water solutions

Preparation of organic‐inorganic composite membranes and their pervaporation (PV) permeation and separation characteristics for the aqueous solution of ethyl acetate were described. Polyacrylonitrile (PAN) hollow fiber ultrafiltration membrane as support membrane, the mixtures of perfluorosulfonic acid (PFSA) and tetraethoxysilane (TEOS) by the sol‐gel reaction as the coating solution, the PFSA‐TEOS/PAN hollow fiber composite membranes by the different annealing conditions were prepared. The swelling of PFSA in ethyl acetate aqueous solutions was inhibited with addition of TEOS. The PFSA‐TEOS/PAN composite membranes containing up to 30 wt % TEOS in coating solution exhibited high selectivity towards water, then the selectivity decreased and permeation flux increased with increasing the TEOS concentration more than 30 wt %. When the PFSA‐TEOS/PAN composite membranes were annealed, the separation factor increased with increasing annealing temperature and time. Higher annealing temperature and longer annealing time promoted the crosslinking reaction between PFSA and TEOS in PFSA‐TEOS/PAN composite membranes, leading to the enhanced selectivity towards water. For the PFSA/PAN and PFSA‐TEOS/PAN composite membrane with 5 and 30 wt % TEOS annealed at 90°C for 12 h, their PV performance of aqueous solution 98 wt % ethyl acetate were as follows: the separation factors were 30.8, 254 and 496, while their permeation flux were 1430, 513 and 205 g/m² h at 40°C, respectively. In addition, the PV performance of PFSA‐TEOS/PAN composite membranes was investigated at different feed solution temperature and concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of PFSA‐PVA/PSf hollow fiber membrane for IPA/H2O pervaporation process

Using Na⁺ form of perfluorosulfonic acid (PFSA) and poly(vinyl alcohol) (PVA) as coating materials, polysulfone (PSf) hollow fiber ultrafiltration membrane as a substrate membrane, PFSA‐PVA/PSf hollow fiber composite membrane was fabricated by dip‐coating method. The membranes were post‐treated by two methods of heat treatment and by both heat treatment and chemical crosslinking. Maleic anhydride (MAC) aqueous solution was used as chemical crosslinking agent using 0.5 wt % H₂SO₄ as a catalyst. PFSA‐PVA/PSf hollow fiber composite membranes were used for the pervaporation (PV) separation of isopropanol (IPA)/H₂O mixture. Based on the experimental results, PFSA‐PVA/PSf hollow fiber composite membrane is suitable for the PV dehydration of IPA/H₂O solution. With the increment of heat treatment temperature, the separation factor increased and the total permeation flux decreased. The addition of PVA in PFSA‐PVA coating solution was favorable for the improvement of the separation factor of the composite membranes post‐treated by heat treatment. Compared with the membranes by heat treatment, the separation factors of the composite membranes post‐treated by both heat treatment and chemical crosslinking were evidently improved and reached to be about 520 for 95/5 IPA/water. The membranes post‐treated by heat had some cracks which disappeared after chemical crosslinking for a proper time. Effects of feed temperature on PV performance had some differences for the membranes with different composition of coating layer. The composite membranes with the higher mass fraction of PVA in PFSA‐PVA coating solution were more sensitive to temperature. It was concluded that the proper preparation conditions for the composite membranes were as follows: firstly, heated at 160°C for 1 h, then chemical crosslinking at 40°C for 3 h in 4% MAC aqueous solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

全氟磺酸改性聚乙烯醇渗透汽化膜分离乙酸乙酯-水溶液

以聚乙烯醇(PVA)为原材料,全氟磺酸(PFSA)为共混改性材料,以聚丙烯腈(PAN)中空纤维超滤膜为底膜制备了PVAfPAN、PVA-PFSA/PAN复合膜,并用于乙酸乙酯脱水.考察了共混涂膜液中PVA、PFSA配比,交联剂酒石酸(Tat)用量以及原料液温度与浓度对PVA、PAN、PVA-PFSA、PAN复合膜分离件能的影响.实验结果表明,Tac交联的PVA,PAN、PVA-PFSA/PAN复合膜均对水具有较好的分离选择性.共混涂膜液中PVA/PFSA质量比为1/1、Tac/PVA质量比为l/5时所制备的PVA-PFSA/PAN复合膜渗透汽化分离性能最佳.40下℃此复合膜用于分离98%(wt)的乙酸乙酯水溶液时,其渗透通量和分离因予分别为81.1 g·m-2·h-1和1890.同样条件下,与交联PVA/PAN复合膜相比,交联PVA-PFSA/PAN复合膜的渗透通量显著提高.     

Pervaporation characteristics and structure of poly(vinyl alcohol)/poly(ethylene glycol)/tetraethoxysilane hybrid membranes

Poly(vinyl alcohol) (PVA) blended with poly(ethylene glycol) (PEG) was crosslinked with tetraethoxysilane (TEOS) to prepare organic–inorganic PVA/PEG/TEOS hybrid membranes. The membranes were then used for the dehydration of ethanol by pervaporation (PV). The physicochemical structure of the hybrid membranes was studied with Fourier transform infrared spectra (FT‐IR), wide‐angle X‐ray diffraction WXRD, and scanning electron microscopy (SEM). PVA and PEG were crosslinked with TEOS, and the crosslinking density increased with increases in the TEOS content, annealing temperature, and time. The water permselectivity of the hybrid membranes increased with increasing annealing temperature or time; however, the permeation fluxes decreased at the same time. SEM pictures showed that phase separation took place in the hybrid membranes when the TEOS content was greater than 15 wt %. The water permselectivity increased with the addition of TEOS and reached the maximum at 10 wt % TEOS. The water permselectivity decreased, whereas the permeation flux increased, with an increase in the feed water content or feed temperature. The hybrid membrane that was annealed at 130°C for 12 h exhibited high permselectivity with a separation factor of 300 and a permeation flux of 0.046 kg m^?2 h^?1 in PV of 15 wt % water in ethanol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Pervaporation study of ethylene glycol dehydration through synthesized (PVA–4A)/polypropylene mixed matrix composite membranes

Poly(vinyl alcohol) (PVA)/zeolite 4A mixed matrix composite membranes supported on polypropylene microfiltration membranes were prepared by solution casting method and crosslinked with glutaraldehyde to investigate their pervaporation (PV) separation properties of water–ethylene glycol mixtures. Scanning electron microscopy images showed homogeneous distribution of zeolite nanoparticles within the polymer matrix without any visible macroscopic voids at the zeolite–polymer interface. The PV experiments were accomplished to investigate the effects of water concentration (10–40 wt%) and temperature (60–80°C) on separation performance of the membranes. It was found out that 5 wt% loading of the 4A nanoparticles into the PVA matrix is optimal to obtain the best separation performance. The experimental results revealed that loading of zeolite 4A enhanced the membrane performance [both permeation flux (5%) and separation factor (32%) at 5 wt% zeolite loading]. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

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

In 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.     

Titanate nanotubes-embedded chitosan nanocomposite membranes with high isopropanol dehydration performance

Titanate nanotubes (TNTs) are prepared by a hydrothermal method, and then modified with poly(aspartic acid). Subsequently, they are incorporated into chitosan (CS) to fabricate the modified TNTs (MTNTs)-embedded chitosan hybrid membranes supported by the polyacrylonitrile (PAN) membrane (CS-MTNTs/PAN) and utilized for isopropanol dehydration. The physicochemical properties including physical morphology, chemical interaction, hydrophilicity, crystallinity, thermal stability and free-volume of CS-MTNTs hybrid separation layers are characterized by SEM, FTIR, water contact angle, XRD, TG and PALS analysis, respectively. It is found that the modification of poly(aspartic acid) can apparently improve the interfacial morphology and compatibility between TNTs and membrane matrix. Moreover, the superior isopropanol dehydration performance of CS-MTNTs/PAN composite membranes compared to pure CS membrane is verified via pervaporation experiments, which can be ascribed to the strong hydrophilicity and tubular structure of TNTs. For 90 wt% aqueous solution of isopropanol, the CS-MTNTs/PAN composite membrane containing 6 wt% MTNTs acquires the highest permeation flux and separation factor of 1498 g/m² h and 6237 at 80 °C, respectively. These results indicate the promising application potential of nanotube-filled membranes in the pervaporative dehydration of alcohols.     

PFSA-TiO2(or Al2O3)-PVA/PVA/PAN difunctional hollow fiber composite membranes prepared by dip-coating method

PFSA-TiO₂(or Al₂O₃)-PVA/PVA/PAN difunctional hollow fiber composite membranes with separation performance and catalytic activity have been prepared by dip-coating method. The good separation performance was brought about by the glutaraldehyde (GA) surface cross-linked PVA/PAN composite membrane, and the good catalytic activity of the membrane was achieved by the perfluorosulphonic acid (PFSA) used. The difunctional hollow fiber membranes were characterized by XRD, TGA, EDX, SEM, and FTIR. The separation performance was measured by dehydration of azeotropic top product of ethanol-acetic acid esterification, and the catalytic activity was obtained by investigating the esterification of ethanol and acetic acid. The FTIR spectra and the morphologies of difunctional hollow fiber composite membranes were similar for samples prior to esterification and post-esterification with ethanol and acetic acid for 24?h. Difunctional hollow fiber composite membranes with 2% PFSA, 8% TiO₂ (named as DM-T1), and 2% PFSA, 8% Al₂O₃ (named as DM-A1) (all by weights) showed the best catalytic activity. They displayed fluxes of 165 and 173?g/m^2?h, separation factors of water to ethanol of 279 and 161, PFSA contents in difunctional hollow fiber composite membrane of 3.2 and 2.4%, the ratios of PFSA to feed solution (acetic acid?Cethanol) of 0.031 and 0.023%, and the equilibrium conversion of ethanol at 53.5 and 57.6%, in the given order for TiO₂ and Al₂O₃ containing samples.     

Hybrid sol–gel membranes of polyacrylonitrile–tetraethoxysilane composites for gas permselectivity

Sol–gel reaction of tetraethoxysilane (TEOS) with fumed silica–polyacrylonitrile (PAN) membrane was carried out to prepare hybrid gas permeable membranes for oxygen and nitrogen separation. Various amounts of fumed silica microparticles with a few μm diameters were compounded in PAN–dimethylsulfoxide (DMSO) solution. After casting of the viscous compound solution on a flat sheet with 100 μm thickness, DMSO was evacuated under vacuum at 80°C. Then, the silica–PAN composite membranes were treated with TEOS for 1 day at 40°C in methanol. Air permeation was examined and compared in silica–PAN composite membranes with and without TEOS treatment. The latter hybrid membranes showed selective oxygen permeability, which depended on amounts of fumed silica in the membrane. The TEOS hybrid PAN membranes have a high ability of oxygen permselectivity for O₂/N₂ gas mixture with α(O₂/N₂) = 13–17, when the silica content was in the range of 13–20 wt %. This is attributed to siloxane network formation in hybrid silica–PAN composite membranes. Favorable siloxane network formation resulted in high oxygen permeability of the hybrid composite membranes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1752–1759, 2003     

Pervaporation of Acetaldehyde Aqueous Solution through Zeolite 3A-Polyurethane (PU) Composite Membrane

3A-filled hydrophilic polyurethane (PU) membranes were prepared by incorporating zeolite 3A into PU for pervaporation separation of acetaldehyde and water mixtures (acetaldehyde concentration 2 wt%–20 wt%). The composite membranes were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The morphology and thermal stability of these membranes were also investigated. The effects of zeolite 3A on the sorption, diffusion, and pervaporation performance were evaluated. The swelling study showed that 3A-PU membrane had higher swelling degree in acetaldehyde aqueous solution than in pure water. And the swelling degree of the composite membrane in acetaldehyde solution increased with the 3A content. The permeation flux and water/acetaldehyde separation factor first increased and then decreased with increasing 3A content. The reason may be that a proper quantity of 3A will enlarge the free volume fraction of PU while excessive 3A lead to its poor dispersion. The highest permeation flux of the composite membrane could reach 223 g · m^?2 · h^?1 and the maximum water/acetaldehyde selectivity achieved 7.5. The calculation of sorption selectivity and diffusion selectivity showed that diffusion played a more important role in this process.     

PVA-TEOS/PAN渗透汽化膜的制备及其乙酸乙酯脱水

以聚丙烯腈(PAN)中空纤维超滤膜为底膜,以聚乙烯醇(PVA)和正硅酸乙酯(TEOS)的混合液为涂膜液,采用溶胶-凝胶法制备了PVA-TEOS/PAN渗透汽化复合膜,并用于乙酸乙酯脱水. FT-IR和XRD谱图证实复合膜表层中由于PVA与TEOS的交联反应而形成了Si?O?C共价键,且PVA的结晶度下降. 另外,利用静态接触角测量对复合膜表层的亲水性进行了表征. 考察了复合膜在乙酸乙酯水溶液中的溶胀性能及涂膜液中TEOS含量和料液温度与浓度对PVA-TEOS/PAN复合膜分离性能的影响. 结果表明,TEOS的加入有效降低了复合膜在乙酸乙酯水溶液中的溶胀度,使其对水具有较好的分离选择性. 40℃下,涂膜液中TEOS质量含量分别为5%和30%的PVA-TEOS/PAN复合膜分离98%的乙酸乙酯水溶液时,其分离因子分别为2830和4448,渗透通量分别为49.4和41.4 g/(m2×h).     

Study of pervaporation for dehydration of caprolactam through PVA/nano silica composite membranes

We investigated nano silica/PVA composite membranes to propose an improved caprolactam pervaporation (PV) dehydration process. The membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and contact angle measurement. Compared with the pure PVA membranes, the nano silica/PVA composite membranes showed different surface morphologies with enhanced hydrophilicity because of their unique formation. To evaluate PV performance and mechanism, we assessed the permeation flux, separation factor, diffusivity/sorptivity selectivity, and activation energy of the composite membranes. The evaluated results indicate that the nano silica/PVA composite membranes induced a breakthrough in the dehydration of a caprolactam-water mixture with a maximum flux of 3.8 kg m^? 2 h^? 1 and an acceptable separation factor of 150.     

Preparation and characterization of a poly(vinyl alcohol)/tetraethoxysilane ultrafiltration membrane by a sol–gel method

Using poly(vinyl alcohol) (PVA) with highly hydrophilic properties as membrane material and poly(ethylene glycol) (PEG) as an additive, we prepared PVA/tetraethoxysilane (TEOS) ultrafiltration (UF) membranes with good antifouling properties by a sol–gel method. The PVA/TEOS UF membranes were characterized by X‐ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron microscopy, and static contact angle of measurement of water. The hybridization of TEOS to PVA for preparing the PVA/TEOS UF membranes achieved the required permeation performance and good antifouling behaviors. The morphology and permeation performance of the PVA/TEOS membranes varied with the different TEOS loadings and PEG contents. The pure water fluxes (J_W) increased and the rejections (Rs) decreased with increasing TEOS loading and PEG content. The PVA/TEOS UF membrane with a PVA/TEOS/PEG/H₂O composition mass ratio of 10/3/4/83 in the dope solution had a J_W of 66.5 L m^?2 h^?1 and an R of 60.3% when we filtered it with 300 ppm of bovine serum albumin aqueous solution at an operational pressure difference of 0.1 MPa. In addition, the filtration and backwashing experiment proved that the PVA/TEOS membranes possessed good long‐term antifouling abilities. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4066–4074, 2013     

Comparative behavior of PVA/PAN and PVA/PES composite pervaporation membranes in the pervaporative dehydration of caprolactam

Flat‐sheet composite membranes were developed by the traditional phase inversion technique using poly;(vinyl alcohol) (PVA). PVA composite pervaporation (PV) membranes were prepared with crosslinked PVA selective layer and porous polyacrylonitrile (PAN) and polyether sulfone (PES) substrate layer material as supports for separating heat sensitivity substance ε‐caprolactam (CPL) from CPL/water mixtures. Glutaraldehyde was used as crosslinking agent. The effect of the composition of glutaraldehyde on membrane stability and structure were investigated. The operating parameters, such as feed concentration and operating temperature, remarkably affected PV performance of the composite membranes. The composite membranes with PVA casted on PAN (PVA/PAN) showed superior PV performance than that casted on PES (PVA/PES). This study has also shown that the type of porous support plays an important role in the PV performance. As a result, this work has presented the information needed of the behavior of PV membranes for dehydration applications of industrial caprolactam. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4005–4011, 2007     

Separation Characteristics of Dimethylformamide/Water Mixtures through Alginate Membranes by Pervaporation,Vapor Permeation and Vapor Permeation with Temperature Difference Methods

Abstract

In this study permeation and separation characteristics of dimethylformamide (DMF)/water mixtures were investigated by pervaporation (PV), vapor permeation (VP), and vapor permeation with temperature difference (TDVP) methods using alginate membranes crosslinked with calcium chloride. The effects of membrane thickness (30–90 µm), feed composition (0–100 wt%), operating temperature (30–50°C) on the permeation rates and separation factors were investigated. The permeation rate was found to be inversely proportional to the membrane thickness whereas separation factor increased as the membrane thickness was increased. It was observed that the permeation rates in VP and TDVP were lower than in PV however the highest separation factors were obtained with TDVP method. Alginate membranes gave permeation rates of 0.97–1.2 kg/m² h and separation factors of 17–63 depending on the operation conditions and the method. In addition, sorption‐diffusion properties of the alginate membranes were investigated at the operating temperature and the feed composition. It was found that the sorption selectivity was dominant factor for the separating of DMF/water mixtures.     

Enhancement of pervaporation performance of composite membranes through in situ generation of silver nanoparticles in poly(vinyl alcohol) matrix

Composite membranes were prepared from an aqueous solution of poly(vinyl alcohol) (PVA) and silver sulphate. The silver nanoparticles were generated in situ before crosslinking PVA matrix by reduction of silver ions using sodium borohydride. Physico‐chemical properties of the resulting composite membranes were studied using Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy (UV–vis), thermogravimetric analysis (TGA), Wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), and universal testing machine (UTM). The UV–vis spectrum shows a single peak at 410 nm due to surface plasmon absorption of silver nanoparticles. This surely specified that silver nanoparticles are generated in PVA matrix. The membranes were under go pervaporation (PV) for separation of water from isopropanol at different temperatures. The results indicated that hydrophilicity and amorphous nature of the membranes were increased with increasing silver nanoparticles in PVA matrix. The swelling and separation performance of the membranes were studied. Both permeation flux and separation factor were increased with increasing silver nanoparticles in PVA matrix. The results showed that the membrane containing 2.5 mass% of Ag salt exhibited excellent PV performance. The values of total flux and flux of water are almost closed to each other, indicating that membranes could be effectively used to break the azeotropic point of water‐isopropanol. The long‐term test was performed at room temperature and ascertained that membranes were durable up to 30 days for the dehydration of IPA. On the basis of the estimate Arrhenius activation energy values, the efficiency of the membranes was discussed. The calculated ΔH_s values are negative for all the membranes, indicating that Longmuir's mode of sorption is predominant. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41248.     

Preparation of crosslinked alginate composite membrane for dehydration of ethanol–water mixtures

The purpose of this article was to develop new membranes with a high selectivity and permeation rate for separation of an alcohol/water system. Crosslinked alginate composite membranes were prepared by casting an aqueous solution of alginate and 1,6‐hexanediamine (HDM) onto a hydrolyzed microporous polyacrylonitrile (PAN) membrane. The influence of hydrolysis of the support membrane and crosslinking agent content in a dense layer on the selectivity and flux was studied and it was shown that both could improve the separation performance of the composite membrane greatly. The countercation of alginate coatings as a dense separating layer also influenced the separation properties of the membrane, which was better for K⁺ than for Na⁺. This novel composite membrane with K⁺ as a counterion has a high separation factor of 891 and a good permeation rate of 591 g m⁻² h⁻¹ for pervaporation of a 90 wt % ethanol aqueous solution at 70°C. At the same time, SEM micrographs showed that the pore structure of the PAN microporous membrane is changed by hydrolysis. The reason for the influence of the preparation conditions on the separation performance of the novel membrane is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3054–3061, 2000     

Pervaporation properties of polyvinyl alcohol/ceramic composite membrane for separation of ethyl acetate/ethanol/water ternary mixtures

In further purification of ethyl acetate (EAC) process, azeotropic distillation or extractive distillation is usually applied. High energy consumption limits the economic profit of the process. In this study, pervaporation separation of EAC/ethanol (EA)/water ternary mixtures using the ceramic-supported polyvinyl alcohol (PVA) composite membrane was investigated to substitute the azeotropic distillation or extractive distillation. Swelling experiments were performed to evaluate the sorption characteristic of the membrane. Flory-Huggins theory was applied to study the interaction between the membrane and the penetrant. The UNIFAC model was adopted to investigate the variation of the penetrant activity in the membrane. The effects of operation temperature, feed water content and feed flow rate on the PV performance of the membrane were systematically investigated. The composite membrane exhibited high PV performance with the total flux of 2.1 kg·m⁻²·h⁻¹ and 94.9 wt% permeate concentration of water (operation condition: feed composition 82.6 wt% EAC, 8.4 wt% EA, 9 wt% water, feed temperature 60 °C, feed flow rate 252 mL· min⁻¹). The PV performance of the membrane varied slightly over a continuous PV experiment period of 110 h. Our results demonstrated that the PVA/ceramic membrane was a potential candidate for the purification of EAC/EA/water ternary mixtures.     

聚乙烯醇-二氧化硅/聚丙烯腈杂化复合膜渗透蒸发分离己内酰胺/水溶液

制备了以聚乙烯醇(PVA)填充纳米SiO2改性膜为活性层,聚丙烯腈(PAN)超滤膜为底膜的PVA-SiO2/PAN杂化复合膜,并用于己内酰胺(CPL)脱水。用FTIR,SEM,XRD,TGA分别对膜进行了表征,并考察了膜中纳米SiO2粒子的质量分数、进料组分质量分数和温度对复合膜分离性能的影响。结果表明,引入纳米SiO2后,杂化膜的热稳定性明显提高。当膜中纳米SiO2质量分数为1.0%时,复合膜渗透蒸发分离性能最佳。60℃下此复合膜用于分离质量分数为40%的CPL溶液时,其总通量和分离因子分别达到2 177 g/(m2.h)和349。     

Optimization of Preparation Conditions for PDMS-Silica Composite Pervaporation Membranes Using Response Surface Methodology

In this article, response surface methodology was used to optimize the preparation conditions of fumed silica filled polydimethylsiloxane/cellulose acetate composite membranes. The silica loading, polydimethylsiloxane concentration, and NH₂-C₃H₆-Si(OC₂H₅)₃/silica weight ratio were considered as factors. Two regression equations, which described the effects of the three factors on the permeation flux and selectivity of the membranes, were derived from the results of 20 experiments by using a statistical software Design-Expert 7.1.4. The results revealed that the three factors had important effects on the permeation flux and the selectivity. The obtained regression equations were confirmed with another four groups of experiments. According to the regression equations, for the separation of an ethanol aqueous solution with the concentration of 10 wt%, the maximum selectivity of the membrane, 11.5 could be obtained at the feed temperature of 40°C, and the corresponding permeation flux was 197.3 g · m^?2 · h^?1. The preparation conditions for making the composite membrane with the above separation performances were: the silica loading was 5.21 wt%, the polydimethylsiloxane concentration was 13.36 wt%, and the NH₂-C₃H₆-Si(OC₂H₅)₃/silica weight ratio was 0.59.