Preparation and thermal treatment of Pd/Ag composite membrane on a porous α-alumina tube by sequential electroless plating technique for H2 separation

Pd/Ag/α-Al2O3 composite membranes were prepared by sequential electroless plating technique. The prepared membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spec-troscopy, and inductively coupled plasma atomic emission spectroscopy techniques (ICP-AES). Effects of annealing time, Ag content, and air treatment on the hydrogen permeation flux and morphology of the alloys were investigated. The results of the investigation showed that the prepared type of tube had a good potential as substrate for membrane preparation. In addition, a uniform defect-free alloy was prepared by annealing at 550 ℃ in H2 atmosphere. The permeation results showed an increase in H2 permeation flux by increasing the Ag content and the annealing time. In addition, the air treatment of the prepared membranes at 400 ℃ for 1 h changed the morphology of the alloy and substantially enhanced the hydrogen flux.     

Effect of nickel deposition on hydrogen permeation behavior of mesoporous gamma-alumina composite membranes

Ni/alumina composite membranes were prepared and investigated for hydrogen separation at high temperature. alpha-Alumina-supported gamma-alumina composite membranes were prepared by soaking-rolling method. In order to improve H2 selectivity and permeance of the gamma-alumina membranes, Ni was deposited by a soaking process. As a result of a single gas permeation test of the Ni/alumina composite membranes, hydrogen permeance and H2/N2 selectivity at permeation temperature of 450 degrees C were 6.29 x 10(-7) mol/m2 s Pa and 5.2 which exceeded theoretical Knudsen selectivity. Contribution of surface diffusion was investigated by temperature dependence of H(2) permeance. The surface diffusion was observed at higher temperature above 250 degrees C. The Ni deposition on surface of the gamma-alumina composite membrane led to hydrogen permeation via Knudsen diffusion combined with surface diffusion, which gave high H2 selectivity exceeding the Knudsen diffusion mechanism.     

Preparation and characterization of polyvinylidene fluoride (PVDF) hollow fiber membranes

Polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared by dry/wet and wet phase inversion methods. In spinning these PVDF hollow fibers, dimethylacetamide (DMAc) and polyvinyl pyrrolidone (PVP) were used as a solvent and an additive, respectively. Water was used as the external coagulant. Water or ethanol was used as the internal coagulants. The membranes were characterized in terms of water flux, molecular weight cut-off for the wet membranes. Gas permeation fluxes and effective surface porosity were determined by a gas permeation method for the dried membranes. The cross-sectional structures were examined by scanning electron microscopy. The effects of polymer concentration, air-gap, PVP molecular weight, PVP content in the polymer dope, and the internal coagulant on the permeation properties and membrane structures were examined. Highly permeable PVDF hollow fiber membranes could be prepared from a polymer dope containing low molecular weight PVP and using ethanol as the internal coagulant.     

Vapor permeation of ethanol-water mixtures using sodium alginate membranes with crosslinking gradient structure

For the vapor permeation of ethanol-water mixtures, two types of dense sodium alginate (SA) membranes have been prepared: a nascent SA membrane and crosslinked SA membranes with glutaraldehyde (GA). In the vapor permeation of the concentrated ethanol-water mixtures through the SA membranes, the effects of feed temperature, cell temperature and crosslinking density in the membrane were investigated on the membrane performance, and a comparison of vapor permeation process was made with pervaporation. SA membranes having different crosslinking gradients have been fabricated by exposing the nascent membrane to different GA content of reaction solutions. The extent of the gradient was controlled by the exposing time. The permeation performance of the membranes will be discussed with the extent of the gradient. An optimal crosslinking gradient was determined in terms of flux and membrane stability. The separation of ethanol-water mixtures through the membrane with the optimal crosslinking gradient was carried out by vapor permeation and the permeation performance will be discussed, and compared with pervaporation.     

孔雀石绿分子印迹膜的制备和渗透性

以0.45 μm混合纤维素酯微孔膜为支载膜,丙烯酰胺为功能单体,N, N'-亚甲基双丙烯酰胺为交联剂,通过原位聚合法制备得到孔雀石绿分子印迹膜,并研究了其对模板分子和类似物的渗透性能。以分子印迹膜作为渗透膜,单一渗透实验中,13 h后MG的渗透量达到0.118×10^-3 g/cm²,而相同时间内甲基紫、甲酚红和溴百里酚蓝的渗透量分别为0.064×10^-3、0.057×10^-3和0.044×10^-3 g/cm²,且在竞争渗透中孔雀石绿的渗透速率没有发生明显变化,而甲基紫的渗透速率却显著下降。实验表明,分子印迹膜对模板分子孔雀石绿表现出良好的渗透选择性,且在与类似物甲基紫的竞争渗透中具有优先渗透能力。     

Preparation and thermal treatment of Pd/Ag composite membrane on a porous alumina tube by sequential electroless plating technique for H2 separation

Pd/Ag/α-Al2O3 composite membranes were prepared by sequential electroless plating technique. The prepared membranes were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive spectroscopy, and inductively coupled plasma atomic emission spectroscopy techniques （ICP-AES）. Effects of annealing time, Ag content, and air treatment on the hydrogen permeation flux and morphology of the alloys were investigated. The results of the investigation showed that the prepared type of tube had a good potential as substrate for membrane preparation. In addition, a uniform defect-free alloy was prepared by annealing at 550 ℃ in H2 atmosphere. The permeation results showed an increase in H2 permeation flux by increasing the Ag content and the annealing time. In addition, the air treatment of the prepared membranes at 400 ℃ for 1 h changed the morphology of the alloy and substantially enhanced the hydrogen flux.     

Fabrication and evaluation of molecularly imprinted regenerated cellulose composite membranes via atom transfer radical polymerization

A simple and effective method for surface molecularly imprinted composite membranes （MICMs） for artemisinin （Ars） based on regenerated cellulose membranes was first prepared through surface- initiated atom transfer radical polymerization （ATRP）, and the as-prepared MICMs were then evaluated as adsorbents for selective recognition and separation of Ars molecules. Batch rebinding studies were conducted to determine the specific adsorption equilibrium, kinetics and selective permeation performance. The adsorption capacity of MICMs toward Ars by the Langmuir isotherm model was 2.008 mgg-1, which was nearly 5.0 times higher than non-molecularly imprinted composite membranes （NICMs）. The kinetic property of MICMs was well-fitted by the pseudo-second-order rate equation. The selective permeation experiments were successfully investigated to prove the excellent selective permeation performance for Ars than the competitive analog （artemether）.     

Pervaporation dehydration of isopropanol with chitosan membranes

Homogeneous and composite chitosan based membranes were prepared by the solution casting technique. The membranes were investigated for the pervaporation dehydration of isopropanol-water systems. The effects of feed concentration and temperature on the separation performance of the membranes were studied. In terms of the pervaporation separation index (PSI), the composite membrane was more productive than the homogeneous membrane for pervaporation of feed with high isopropanol content. It was observed that permeation increased and the separation factor decreased with the temperature. Modification of the homogeneous chitosan membrane by chemical crosslinking with hexamethylene diisocyanate improved the permselectivity but reduced the permeation rate of the membrane.     

Preparation and characterization of silicalite-1 membranes prepared by secondary growth of seeds with different crystal sizes

MFI-type zeolite particles of 0.1–1 μm in diameter were prepared by adjusting tetra-n-propylammonium hydroxide (TPAOH) and water contents in synthesis mixtures. Using those particles as seeds, MFI-type zeolite membranes were prepared on the surface of a porous mullite tube by secondary growth. The membranes were formed as polycrystalline zeolite layers on and inside the porous support, and the membranes were composed of the [h 0 h]-oriented crystallites. The membrane consisting of a-oriented crystallites could be also prepared. However, the a-oriented zeolite layers were not active on the permeation properties of butanes. Rather the size and loaded amount of the seed particles influenced on the permeation properties through the membranes. As a result, the n-C₄H₁₀/i-C₄H₁₀ permselectivity could be increased to 220 by adjusting the size and the loaded amount of particles. These results suggest that the number of loaded particles affects on the permeation properties through the membranes.     

High-performance membranes for pervaporation II. Crosslinked poly(vinyl alcohol)–poly(acrylic acid) blends

Dense membranes made by crosslinking of poly(vinyl alcohol) (PVA) with poly(acrylic acid) (PAA) were prepared and tested in pervaporation and differential permeation of water–alcohol mixtures. Instead of a decrease of permeation flux as generally observed with most crosslinking agents, an increase in the permeability was observed with PAA crosslinked membranes at low PAA contents. The permeation flux increases with PAA contents in the polymer with no selectivity reduction for membranes containing less than 15 wt. % PAA. The membranes show good performances to water–2-propanol and water–ethanol mixtures, i.e. high fluxes and high selectivities to pure water. The membranes were stable and highly permeable to water. The enhancement of the permeability of PVA can be explained by a reduced crystallinity and an improved diffusivity due to the presence of PAA.     

Polyurethane IPN membranes

Hydrophilic PU and hydrophobic PS IPN membranes were prepared and the effect of the synthesis pressure on the pervaporation characteristics of ethanol water mixture was evaluated. Cationic/anionic IPN membranes were prepared from the cationic PU and the anionic acrylic copolymer, and the effects of the composition and the ionic concentration on the permeation characteristics were analyzed. The gas (oxygen and nitrogen) transport of the IPN membranes of PU/PS were also examined. The effect of synthesis temperature and composition of the IPN membranes were analyzed.     

溴代聚-4-甲基戊烯-1的溶解性能及其膜的形态结构和结晶状态

<正> 迄今为止,用于气体分离的高分子膜,其气体透过速率和选择分离系数仍不够高。究其原因,一是膜材料的气体透过系数较低;二是某些气体透过系数较高的高分子材料又难以形成超薄膜层。     

Permeation of Liquids through Inorganic Nanofiltration Membranes

Inorganic nanofiltration membranes were prepared using silica-zirconia composite sols by the sol-gel method and applied for the permeation experiments of nonaqueous solutions. Pure solvent permeabilities of methanol, ethanol, and 1-propanol were measured at temperatures from 25 to 60 degrees C. For membranes having pore sizes as large as 70 nm, the permeation mechanism of alcohols obeys the viscous flow mechanism irrespective of types of alcohols. On the other hand, the permeation mechanism through porous silica-zirconia membranes having pore diameters of 1 to 5 nm was found to be different from the viscous flow mechanism; small molecules showed larger permeabilities than large molecules. Activation energies of solvent permeability were found to be larger for large molecules and for membranes of smaller pore size. Copyright 2000 Academic Press.     

Novel SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) membrane for hydrogen separation

<正>Dense ceramic membranes with protonic and electronic conductivity have attracted considerable interest in recent years.In this paper,the powders of SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) were synthesized via the liquid citrate method,and the membranes of SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) were prepared by pressing followed by sintering.X-ray diffraction(XRD) was used to characterize the phase structure of both the powder and sintered membrane.The microstructure of the sintered membranes was studied by scanning electron microscopy(SEM).Hydrogen permeation through the SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) membranes was carried out using gas permeation setup at 900℃.Hydrogen permeation flux of SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) membrane reaches up to 0.042 mL/ min cm~2 at H_2 partial pressure of 0.4 atm.The hydrogen permeation fluxes obtained in this paper are similar to that of SrCe_(0.95)Tm_(0.05)O_(3-δ),and Zr doping can increase mechanical strength of SrCe_(0.75)Zr_(0.20)Tm_(0.05)O_(3-δ) membranes and the resistance to reducing circumstance.     

新型α-纤维素膜制备与性能研究

以N 甲基氧化吗啉为溶剂制备了α 纤维素膜并对其机械性能、液体渗透性能以及耐酸、碱性能进行了考察 .α 纤维素膜机械强度达 133 3MPa ,比其他方法制备的纤维素膜高 30 %～ 6 0 % .α 纤维素膜数对牛血清蛋白的截留率达到 98% ,在pH1至pH9范围内液体渗透流量保持稳定 .文章通过与其他纤维素膜比较 ,进一步揭示了新的制膜方法对纤维素膜结构和性能的影响     

药物氟哌酸分子印迹聚合物膜的制备及其渗透性质研究

以聚偏氟乙烯微孔滤膜为支撑膜,氟哌酸为模板分子,用紫外光引发原位聚合方法制备了分子印迹聚合物膜.研究了模板分子与功能单体之间的相互作用,用扫描电镜表征了膜的表面形貌.混合底物渗透实验结果表明,分子印迹聚合物膜中存在着由形状和功能基团均与模板分子氟哌酸相互补的孔穴组成的通道,该通道可选择性地富集底物分子.     

Comparison between the pervaporation and vapor permeation performances of polycarbonate membranes

The pervaporation and vapor permeation performance of symmetrical and asymmetrical polycarbonate membranes, prepared via a dry-phase inversion and wet-phase inversion methods, respectively, were studied by measuring the permeation rate and separation factor. It was found that the polymer concentration effect on the pervaporation performance for the symmetrical polycarbonate membrane was lower than that for the asymmetrical polycarbonate membrane. Compared with pervaporation, vapor permeation has a significantly increased separation factor with a decreased permeation rate for the symmetrical polycarbonate membrane. Water molecules preferentially dissolve into the symmetrical polycarbonate membrane and diffuse easily through the membrane.     

ZSM-5分子筛填充壳聚糖膜的制备与性能研究

采用液相共混的方法制备了ZSM-5分子筛填充壳聚糖膜.扫描电镜表征表明分子筛在膜中分散均匀,膜表面没有明显缺陷.考察了填充膜在碳酸二甲酯/甲醇混合液中的溶胀和吸附行为,探讨了填充膜中分子筛含量及操作温度对渗透汽化膜分离性能的影响.结果表明膜优先吸附甲醇,其分离性能主要由溶解过程控制;随着膜中分子筛含量的增加,膜的溶胀度增大,渗透通量大幅度提高;渗透通量与操作温度符合Arrhenius关系式.与壳聚糖均质膜相比,ZSM-5分子筛填充壳聚糖膜对甲醇和碳酸二甲酯混合物具有更好的分离效果.     

Study on the variation of morphology and separation behavior of the stainless steel supported membranes at high temperature

Palladium composite membranes were prepared on stainless steel (SUS) supports modified by nickel submicron powder and colloidal silica sols. Permeation tests of the palladium composite membranes were carried out at high temperature in order to observe the thermal stability of the membrane. The palladium composite membrane failed with formation of plenty of pinholes in the presence of hydrogen at high temperature. The failure of the composite membrane was verified by comparing the nitrogen permeance before hydrogen permeation test with that after hydrogen permeation test and comparing the H₂/N₂ selectivity for single gas permeation test with that for mixture gas permeation test. The variation of the membrane surface due to the failure of the membrane was characterized in scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) analyses. As a result, it can be concluded that reducible metal oxides can be attributed to the failure of the composite membranes resulting from reduction of the metal oxides by hydrogen whichever position in the membrane the metal oxides are layered.     

Synthesis and characterization of silicalite-1/carbon-graphite membranes

Silicalite-1/carbon-graphite composite membranes have been prepared using a standard hydrothermal synthesis method and characterized by XRD, SEM, TGA, BET and permeation experiments. Single gas permeation fluxes and binary mixtures separation and selectivity data are reported for methane, ethane and propane using the composite membranes. Carbon-graphite oxidized for 4 h prior to membrane preparation had the most promising separation properties. The permeation fluxes for the binary mixtures reflect that of the single component flux ratios. At 20 degrees C the membranes show high separation selectivity toward lighter component in binary mixtures. Single gas permeances for methane and ethane were found to decrease with increasing temperatures while that of propane fluctuates.