Vapor Permeation and Pervaporation of Aqueous 2‐Propanol Solutions through the Torlon® Poly(amide imide) Membrane

Abstract

In the present study, vapor permeation and pervaporation of aqueous 2‐propanol mixtures were investigated using Torlon^® poly(amide imide) as a membrane material. Torlon membranes preferentially permeated H₂O from aqueous 2‐PrOH mixtures both by vapor permeation and pervaporation. Diffusion experiments led to the conclusion that both solubility selectivity and diffusivity selectivity showed a preference for H₂O. Solubility selectivity is by far the dominant factor governing permselectivity, and as a result, Torlon membranes showed permselectivity toward water in vapor permeation and pervaporation. The present study showed that Torlon^® poly(amide imide) is a membrane material potentially applicable to the dehydration of water miscible organics.     

Separation of Azeotropic Dimethylcarbonate/Methanol Mixtures by Pervaporation: Sorption and Diffusion Behaviors in the Pure and Nano Silica Filled PDMS Membranes

In this article, polydimethylsiloxane and hydrophobic nano-silica filled polydimethylsiloxane membranes were prepared and employed in dimethylcarbonate (DMC) removal from the DMC/methanol mixture via pervaporation. The sorption and diffusion behavior of the binary molecule were discussed separately to provide qualitative estimation of the PV performance in both membranes. Compared with the polydimethylsiloxane membrane, hydrophobic nano-silica filled polydimethylsiloxane membranes had a little lower sorption selectivity but higher diffusion selectivity. In both membranes, the sorption value was obtained by both experimentation and model prediction. The Flory-Huggins model was performed to predict the solvent uptakes and the sorption concentrations based on the experimental results. The sorption behavior of DMC was predictable, while the methanol solubility was a little higher than the experimental results. Moreover, the diffusion behavior was studied by Fick's law, the calculated diffusion coefficients of the permeates demonstrated a diffusion-coupling phenomenon, especially in hydrophobic nano-silica filled polydimethylsiloxane membranes. Methanol molecules diffused faster than DMC, suggesting the low diffusion selectivity. The PV performance was affected by both sorption and diffusion. Sorption was demonstrated to be a decisive factor in this pervaporation process.     

Removal of Volatile Organic Compounds from Water by Pervaporation Using Polyetherimide-Polyethersulfone Blend Hollow Fiber Membranes

Abstract

Removal of volatile organic compounds (VOCs) such as 1,2-dichloroethane, trichloroethylene, chlorobenzene and toluene from water solutions through polyetherimide (PEI)-polyethersulfone (PES) blend hollow fiber membranes was investigated by pervaporation (PV) in this work. The separation performances of the membranes were researched by varying the spinning conditions (such as coagulation temperature and air gap distance) for the preparation of the hollow fibers and the operation conditions (such as velocity, concentration, and temperature of feed liquids). For the PEI-PES blend hollow fiber membrane prepared when the air gap was 7 cm and the temperature of coagulation bath was 45°C, it possessed high selectivity to the aqueous solutions containing 0.04 wt.% of VOCs at 20°C. The separation factors to 1,2-dichloroethane, trichloroethylene, chlorobenzene and toluene were 7069, 5759, 3952, and 3205, respectively. It was found that the pervaporation performance of the blend hollow fiber membrane was strongly related to the molecular size of the VOCs. The order of the selectivities was 1,2-dichloroethane > trichloroethylene > chlorobenzene > toluene.     

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.     

膜渗透蒸发/GC-MS测定纺织品中多氯联苯

采用膜渗透蒸发/气相色谱-质谱联用技术,建立了纺织品中多氯联苯的测定方法。优化的试验条件为料液浓度50~1 000 μg/L,温度43 ℃,Na2SO4含量0~1%,流速380 mL/min。本方法对目标化合物的检测限均低于0.03 mg/L,加标回收率在76.66%～118.71%,相对标准偏差小于12%。     

酒精发酵液硅沸石膜渗透气化分离的分离特性

考察了酒精发酵液的组成对利用硅沸石膜进行渗透气化分离时的分离特性的影响，提出了在酒精发酵液中，由于发酵过程中产生的大量有机高分子化合物，以及添加一定浓度的无机盐，改变了溶液的相平衡和溶液的化学位，从而提高了酒精发酵液中酒精的渗透气化分离特性。     

热浸渍预涂晶种温度对T型分子筛膜性能的影响

通过热浸渍法在α-Al2O3载体管表面预涂晶种,进而制备得到T型分子筛膜,通过XRD和SEM技术对其进行了表征,并在90%(w)异丙醇-10%(w)水体系中评价了T型分子筛膜的渗透汽化性能,考察了第二次涂晶温度和合成时间对T型分子筛膜的形成和分离性能的影响以及T型分子筛膜的重复性。实验结果表明,两次涂晶温度分别为180℃和100℃以及T型分子筛膜的晶化时间为24 h时,所制备的T型分子筛膜在70℃、90%(w)异丙醇-10%(w)水体系中进行渗透汽化性能测定,渗透通量基本大于1.20 kg/(m2·h)、分离因子为3 000~3 600,具有很高的重复性。通过优化第二次涂晶温度及合成时间,能合成出高通量、高重复性的T型分子筛膜。     

γ-（2,3环氧丙氧）丙基三甲氧基硅烷改性海藻酸钠和明胶渗透蒸发杂化膜的制备及乙酸脱水性能研究

通过硅烷偶联剂对海藻酸钠-明胶共混膜进行交联改性制备乙酸脱水渗透蒸发杂化膜。实验结果表明：随着偶联剂含量的增加,杂化膜的对水的选择性先增加后下降,在3 wt%时有最好的选择性,同时膜的渗透通量随着偶联剂含量增加而增大;膜的选择性随着进料乙酸浓度增大而增大,通量随着进料乙酸浓度增大而减少。     

硅橡胶渗透汽化复合膜在丁醇发酵中的应用

丁醇发酵受产物丁醇的抑制,产率和产物浓度低,过程经济性差,为减轻丁醇的抑制,制备了聚二甲基硅氧烷/聚偏氟乙烯(PIMS/PVDF)复合膜用于丙酮-丁醇-乙醇-水体系有机成分的分离.以分离因子和渗透通量为评价指标,考察了料液温度、质量分数和pH值对复合膜渗透汽化分离性能的影响.结果表明:料液温度升高能提高膜的分离性能;料...     

Miscibility studies of sodium carboxymethylcellulose/poly(vinyl alcohol) blend membranes for pervaporation dehydration of isopropyl alcohol

Miscibility studies of sodium carboxymethylcellulose/poly(vinyl alcohol) (NaCMC/PVA) blends of different compositions (100/0, 80 : 20, 60 : 40, 50 : 50, 40 : 60, 20 : 80, and 0 : 100) were investigated using viscometric method. NaCMC, PVA, and their blend membranes were prepared by solution‐casting technique and were then crosslinked with glutaraldehyde (GA). The effect of blend composition on mechanical, swelling, and pervaporation results (flux and selectivity) was also investigated in this study. Attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR) results showed that the blends are miscible over the entire studied composition range and further confirmed the crosslinking reaction with GA. FTIR studies reveal that the blends containing 50 : 50 (NaCMC/PVA) are an optimum miscible blend. Thermogravimetric analysis confirms that the thermal stability increased with increase in NaCMC content in NaCMC/PVA blend membrane. XRD and DSC showed a corresponding decrease in crystallinity and increase in melting point with increase in NACMC content, respectively. NaCMC/PVA blends of all the composition under study were used for dehydration of isopropyl alcohol at different compositions of IPA/water mixture (90 : 10, 87.5 : 12.5, 85 : 15, and 82.5 : 17.5) at 35°C. Swelling studies and PV results reveal that increase in NaCMC content in the blend leads to an increase in flux of water, whereas selectivity decreases. The optimum flux and selectivity were observed for the blend containing 50 : 50 NaCMC/PVA content at a feed ratio of 87.5 : 12.5 IPA/water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011