Fabrication of PES-based nanofiltration membrane modified by composite PAA-co-PMMA-g-ZnA nanoparticles

In the current research, nanocomposite polyethersulfone-based nanofiltration membranes were prepared by composite PAA-co-PMMA-g-ZnA nanoparticles. NF membranes were fabricated by phase inversion through casting solution technique. The effect of composite PAA-co-PMMA-g-ZnA nanoparticles concentration into the casting solution on physicochemical characteristics of membrane was studied. Scanning optical microscopy images showed uniform particle distribution for the membranes. Scanning electron microscopy images also demonstrated that membrane porosity was enhanced by increase in nanoparticles content ratio. The membrane surface 3D images showed smooth surface for the membranes filled with 0.05, 0.1 and 0.5 wt% nanoparticles. The contact angle results exhibited that membrane hydrophilicity was improved significantly by using of NPs in membrane matrix. The contact angle was decreased from 65.38° for PES membrane to 48.33° for membrane filled with 0.5 wt% nanoparticles. The water permeability was reduced initially by addition of 0.05 wt% nanoparticles into the casting solution and then increased by more nanoparticles loading rate (0.1 wt%). The water permeability was decreased again by more increase in nanoparticles loading range from 0.5 to 1 wt%. The salt rejection was improved strongly from 68.4 % for PES to 88.58 % for membrane filled with 0.5 wt% nanoparticles. The membranes mechanical strength was increased sharply from 2835.5 to 3337.3 kPa with addition of nanoparticles into the casting solution.     

NafionTM膜表面改性用等离子体聚合方法提高膜的阳离子选择性

采用辉光放电等离子体聚合方法 ,以 C2 H4 和 NH3 为单体 ,在 Nafion TM膜表面沉积一层含氨基及酰氨基的类聚乙烯阴离子交换膜 ,提高了 Nafion TM膜对阳离子的选择性 ,同时不显著增加膜电阻 .由 SEM确定该等离子体聚合膜厚约 0 .5μm,用红外光谱及 X光电子能谱表征膜结构 .采用四电极法测量膜电阻 ,膜对质子的选择性由 Cu2 + 的迁移数 t Cu表征 ,用二室隔膜装置 (0 .2 5mol/L Cu Cl2 -0 .5mol/L HCl|等离子体处理膜 |1 mol/L HCl)测量 t Cu. O2 等离子体预处理 Nafion TM膜有利于沉积膜在 Nafion TM膜上的沉积并与 Nafion TM膜紧密结合 .经改性后的 Nafion TM膜电阻值仍然很小 ,在 1 mol/L HCl溶液中电阻小于 0 .5Ω· cm2     

混合导体透氧膜反应器中甲烷部分氧化反应的催化行为(英文)

应用组成为Ba0.5Sr0.5Co0.8Fe0.2O3-(的钙钛矿型混合导体陶瓷膜制成膜反应器。该膜在进行氧分离的同时具有活化甲烷氧化偶联的催化功能。随着温度升高和膜的富氧端氧分压的增大,透氧量有所增加。在空气、氦气的氧分压梯度下,850(C,膜厚度为1.5 mm时,JO2可达到1.2 mL/(cm3(min)。同时在800(C~900(C温度范围内,该膜对于甲烷转化为乙烷和乙烯一般只具有0.5%~3.5%的低转化率,而选择性可达40%~70%。在反应尾气中发现了大量的未反应的分子氧,说明过量的氧与甲烷未经催化反应的气相反应导致了C2的选择性相对较低。OCM膜反应模式情况下的透氧量与空气、氦气梯度情况下的透氧量相比只有微小增加,这与POM膜反应模式情况下透氧量大量增加显著不同。     

甲醇浓度对Pt/C催化剂氧还原活性的影响

采用半池考察了Pt/C催化剂在含不同浓度甲醇的0.5mol/L硫酸中的氧还原活性(ORR).研究发现,当甲醇浓度为0.1mol/L时,Pt/C催化剂的ORR活性最高,在催化层上热压商品NafionNRE-212膜后也出现同样趋势.线性扫描伏安曲线显示,压膜前后的Pt/C催化剂的ORR活性在含0.1mol/L甲醇的0.5mol/L硫酸中几乎没有变化.电化学阻抗谱结果表明,在该溶液中,Nafion膜的电阻比在其它电解液中低,这可能是导致Pt/C催化剂ORR活性提高的主要原因.有必要关注Nafion膜的这一异常性质并通过特殊设计后用于电池堆,以提高燃料电池性能.     

氧渗透膜反应器的烷烃氧化脱氢

研究了乙烷和丙烷在催化膜反应器中的氧化脱氢反应．所用的膜材料为La2Ni0.9V0.1O4＋δ和Ba0.5Sr0.5Co0.8Fe0.2O3-δ．为了平衡氧气通量和额外的均匀气相反应,实验选择在中温段进行（550或者650℃）．实验结果表明膜的氧渗透通量和膜表面上主要激活烷烃的活性位在获得高的烷烃转化率过程中起决定性作用．乙烷和丙烷的氧化脱氢实验数据均符合Mars-van Krevelen机理,其中烷烃和膜表面的晶格氧反应产生相应的烯烃．同时证明了气相和膜表面的氧浓度是决定烯烃选择性的关键．     

A dense oxygen separation membrane with a layered morphologic structure

A configuration of dense mixed ionic and electronic conducting (MIEC) membrane with layered morphological structure for oxygen separation, which combines the benefits of high oxygen permeation flux of cobalt-based membrane, high chemical stability of iron-based perovskite and high mechanical strength of thick membrane, was studied. The membrane is normally composed of two layers; each layer is a dense MIEC oxide. The substrate layer is a thick dense membrane with high oxygen permeability but relatively lower chemical stability. The feasibility of dense thick Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF5582) membrane as the substrate layer and Ba_0.5Sr_0.5Co_0.2Fe_0.8O_3−δ (BSCF5528) as the thin-film layer was mainly experimentally investigated. Both the BSCF5582 and the BSCF5528 show the same cubic perovskite structure and the similar lattice constant with no detrimental reaction products formed. By optimizing fabrication parameters of a simple dry pressing process, dual-layered membrane, free of cracks, was successfully fabricated. The oxygen permeation flux of a dual-layered membrane with the thin-film BSCF5528 layer facing to the sweep gas reached 2.1 mL cm⁻² min⁻¹ [STP] (1.56 × 10⁻⁶ mol cm⁻² s⁻¹) at 900 °C, which is about 3.5 times higher than that of the BSCF5528 membrane (0.6 mL cm⁻² min⁻¹, [STP] (4.46 × 10⁻⁷ mol cm⁻² s⁻¹) under the same conditions.     

A method for reducing the flow-sensitivity of a polarographic dissolved-oxygen sensor

A method for reducing the flow-sensitivity of polarographic dissolved-oxygen sensors has been modelled mathematically and tested experimentally. The improved probe uses a two-layer membrane: the first layer is made of Teflon and the second of silicone rubber, which is more permeable than Teflon to oxygen. This arrangement reduces the flow-sensitivity to about 4% of that for a single-membrane 1-mil Teflon; second membrane 2.5-mil silicone rubber. (b) First membrane 0.5-mil Teflon; second membrane 5-mil silicone rubber.     

Oxidative dehydrogenation of propane in a dense tubular membrane reactor

Oxidative dehydrogenation of propane (ODP) to propylene was investigated in a dense tubular membrane reactor made of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) at 700^oC and 750^oC. The propylene selectivity in the membrane reactor (44.2%) is much higher than that in the fixed-bed reactor (15%) at the similar propane conversion (23-27%). Higher propylene selectivity in the membrane reactor was attributed to the lattice oxygen (O^2-) supplied through the membrane. This revised version was published online in June 2006 with corrections to the Cover Date.     

High selectivity of oxidative dehydrogenation of ethane to ethylene in an oxygen permeable membrane reactor

An oxygen permeable membrane based on Ba0.5Sr0.5Co0.8Fe0.2O3-delta is used to supply lattice oxide continuously for oxidative dehydrogenation of ethane to ethylene with selectivity as high as 90% at 650 degrees C.     

Novel Ba_(0.5)Sr_(0.5)Fe_(0.8)Zn_(0.2)O_(3-δ) membranes for POM

A novel cobalt-free perovskite based on Ba_(0.5)Sr_(0.5)Fe_(0.8)Zn_(0.2)O_(3-δ)(BSFZ)were prepared by EDTA-citric acid method.The lattice constants of the BSFZ perovskite were characterized by in situ high-temperature X-ray diffraction(HTXRD).The thermal expansion coefficient of BSFZ is 10.5×10~(-6)K~(-1),which is lower than that of cobalt-based perovskite materials.The BSFZ membrane was also used to construct reactors for the partial oxidation of methane(POM)to syngas.Results show that the BSFZ membrane...     

Transport limitations in ion exchange membranes at low salt concentrations

In this work we show that the electrical resistance of ion exchange membranes strongly depends on the solution concentration: especially at low solution concentrations (<0.1 M NaCl) we observe a very strong increase in electrical resistance of the membrane with decreasing concentration. To understand and clarify this behavior we systematically investigate the influence of the solution concentration on ion transport phenomena in two anion exchange membranes (Neosepta AMX and Fumasep FAD) and two cation exchange membranes (Neosepta CMX and Fumasep FKD) in the concentration range from 0.017 M to 0.5 M NaCl and for different hydrodynamic conditions. The results are highly valuable for processes that operate in the low concentration range (<0.5 M) such as reverse electrodialysis, electrodialysis, microbial fuel cells and capacitive deionization, where the standard membrane characterization values as usually determined in 0.5 M NaCl solutions do not represent the practical application.     

新型抑菌聚砜超滤膜的制备及性能

将辣素功能结构单体N-(4-羟基-3-甲氧基苯甲基)丙烯酰胺(HMBA)和甲基丙烯酸甲酯(MMA)通过自由基引发合成出抑菌型共聚物P(H-co-M), 通过红外吸收光谱和热重分析证实了共聚物的结构. 采用共混法将共聚物引入聚砜(PSF)铸膜液中, 通过浸没沉淀相转化法制备了新型抑菌超滤膜. 考察了P(H-co-M)含量对超滤膜分离性能及抑菌性能的影响. 结果表明, 当P(H-co-M)质量分数为0.5%时, 超滤膜分离性能最佳, 对5 mg/L腐殖酸溶液的稳定水通量为122.2 L/(m2·h), 截留率为84.4%, 与未添加P(H-co-M)的超滤膜相比, 分别提高了19.2%和9.2%. 改性超滤膜具有较强的抑菌性能, 当P(H-co-M)含量为1.0%时, 抑菌率最大(约80.7%).     

纳米碳酸钙/庚二酸复合成核剂对热致相分离法制备聚丙烯微孔膜的影响

以大豆油/邻苯二甲酸二丁酯(DBP)为混合稀释剂,采用热致相分离法(TIPS)制备聚丙烯(PP)微孔膜.研究了纳米碳酸钙成核剂、纳米碳酸钙/庚二酸复合成核剂对PP/大豆油/DBP(30/42/28,质量比)混合体系中PP结晶、熔融性能和PP微孔膜微观结构的影响.结果表明,单一纳米碳酸钙成核剂加入量为PP的0%~4%(质量百分率)时,PP/DBP/大豆油体系中PP熔融曲线上对应的峰值温度(Tpm)降到150.7~151.3℃,而纯PP的熔融峰值温度为165℃;DSC实验结果还显示加入1%~4%纳米碳酸钙和0.5%庚二酸后,导致PP的熔融曲线上出现了熔融双峰,说明纳米碳酸钙/庚二酸复合成核剂与单一成核剂相比有明显地促进β晶生成的作用,宽角X射线衍射(WAXD)实验进一步证实了β晶的存在.单一纳米碳酸钙成核剂对PP微孔膜的球晶结构和微观孔结构影响不大;加入纳米碳酸钙/庚二酸复合成核剂明显影响PP微孔膜的球晶结构和微观孔结构,其中0.5%庚二酸和1%纳米碳酸钙组成的复合成核剂制得的PP微孔膜的球晶结构明显,微孔膜孔径小且分布均匀;进一步增加纳米碳酸钙用量,PP微孔膜生成了许多细小的边界模糊的不规则结晶,微孔膜孔径不规则且尺寸较大,这与此时PP形成β晶结构有关.     

动态膜渗透压法测定生漆多糖水溶液

<正> 生漆是一种性能优异的超耐久涂料,其主要成份为漆酚、漆酶、糖蛋白、多糖和水。多糖由D-半乳糖(65％),4-O-甲基-D-葡萄糖醛酸(24％),D-葡萄糖醛酸(3％),L-阿拉伯糖(4％)和鼠李糖(3％)组成。它带大量支链,在侧链上有大约1/4mol羧基从而显示聚电解质溶液性质。     

Effect of emulsifier type on droplet disruption in repeated shirasu porous glass membrane homogenization

The influence of various emulsifier types (anionic, nonionic, and zwitterionic) on the mean particle size, transmembrane flux, and membrane fouling in repeated membrane homogenization using a Shirasu porous glass (SPG) membrane has been investigated. Oil-in-water (O/W) emulsions (40 wt % corn oil stabilized by 0.06-2 wt % sodium dodecyl sulfate (SDS) or 0.1-2 wt % Tween 20 at pH 3 or 0.5-2 wt % beta-lactoglobulin (beta-Lg) at pH 7) were prepared by passing coarsely emulsified feed mixtures five times through the membrane with a mean pore size of 8.0 microm under the transmembrane pressure of 100 kPa. The flux increased as the number of passes increased, tending to a maximum limiting value. The maximum flux for the Tween 20-stabilized emulsions (5-47 m3.m(-2).h(-1)) was smaller than that for the SDS-stabilized emulsions (29-60 m3.m(-2).h(-1)) because less energy was needed for the disruption of a SDS-stabilized droplet due to the lower interfacial tension. The mean particle size after five passes was 4.1-6.8 and 6.4-8.7 mum for 0.1-2 wt % SDS and Tween 20, respectively. The flux in the presence of beta-Lg was much smaller than that in the presence of SDS and Tween 20, which was a consequence of more pronounced membrane fouling, due to the protein adsorption to the membrane surface. After five passes through the membrane, the fouling resistance in the presence of 2 wt % beta-Lg (1.1 x 10(10) 1/m) was 2 orders of magnitude higher than that for 0.5 wt % Tween 20 and an order of magnitude higher than the membrane resistance. If a clean membrane was used in the fifth pass, a 2-fold reduction of the fouling resistance was observed.     

带酞基聚芳醚酮超滤膜的研究──Ⅰ带酞基聚芳醚酮超滤膜的制备与性能

以带酞基聚芳醚酮（ＰＥＫＭ）为膜材料，用相转换法制备了ＰＥＫ—Ｃ不对称超滤膜，研究了铸膜液的主要组分对膜的孔结构与超滤性能的影响。     

Mass transfer in the membrane concentration polarization layer under turbulent cross flow : II. Application to the characterization of ultrafiltration membranes

Eleven commercial membranes with MW cut-off values between 5,000 and 25,000 daltons have been characterized using a 0.5% Dextran T10 solution as a test substance. In order to predict the concentration at the membrane wall, Sherwood correlations based on various turbulence models have been used. The effects of the roughness of the membrane and viscosity changes due to concentration polarization and suction through the membrane have also been considered. The results have been compared with an uncorrected film theory model in a Reynolds interval of 10000-20000. It is difficult to test the models unless a direct method of estimating the concentration at the membrane wall is developed. However, some conclusions can be drawn about the applicability of the suggested models, according to the type of membrane used. It was also noted that the differences between the models tended to diminish with increasing Reynolds numbers.     

Extraction based on the flow-injection principle: Part 5. Assessment with a Membrane Phase Separator for Different Organic Solvents

Several membrane phase separators have been designed and tested for use in a flow-injection extraction manifold. The membrane is sandwiched between two pieces of perspex with grooves facing the membrane. A PTFE membrane with polyethylene backing proved to be most suitable. With this type of phase separator the total dispersion in the extraction system is less than that obtained with the conventional T-piece separator. Alcohols, alkanes, chlorinated hydrocarbons and aromatic solvents pumped at a flow rate of 0.5–1.0 ml min^-1 can be segmented with aqueous phase and later separated from it with a recovery of up to 95%. The organic phase passing through the detector flow cell is not contaminated by the aqueous phase to any measurable extent.     

Crystallinity enhancement of Nafion electrolyte membranes assisted by a molecular gelator

Nanocrystallites, acting as physical cross-links in Nafion membranes, play a crucial role in building blocks for improving mechanical durability and stopping fuel crossover. However, Nafion membranes suffer from low crystallinity due to the irregular pendent side chains, which hinder self-aggregation of the poly(tetrafluoroethylene) (PTFE) backbones. For the first time, a molecular gelator was introduced in the membrane casting process to enhance the rate of self-assembly of PTFE backbones so as to increase the membrane's crystallinity as well as proton conductivity without sacrificing the purity of Nafion. The molecular gelator used was 3,4-dimethylbenzaldehyde (DMBA). Addition of 0.5 wt % DMBA led to a 42% increase in crystallinity, a 32% increase in yield strength, a 22% increase in tensile modulus and an 18% increase in proton conductivity at 60 °C and 90% relative humidity. Additionally, the membrane electrode assembly (MEA) prepared from the membranes cast from the solution containing 0.5 wt % DMBA also showed an increase of 17% in maximum power density in comparison to the MEA prepared from pure Nafion membrane in a single cell polarization test without any external humidification. Transmission electron microscopy (TEM) and molecular dynamics simulation were used to elucidate the structural changes in Nafion membrane due to the introduction of DMBA. It was observed that the presence of DMBA gives wider crystalline regions under TEM. The molecular dynamics simulation at 500 K shows that the PTFE backbones become elongated in the presence of DMBA due to the enhanced mobility. This is consistent with the observed increase in crystallinity in the membrane as it means reduced entropic change upon crystallization.     

Chitosan‐modified graphene oxide as a modifier for improving the structure and performance of forward osmosis membranes

Chitosan (CS) with good hydrophilicity and charged property was used to modify graphene oxide (GO), the obtained GO‐CS was used as a novel modifier to fabricate thin film composite forward osmosis (FO) membranes. The results revealed that the amino groups on CS reacted with carboxyl groups on GO, and the lamellar structure of the GO nanosheets was peeled off by CS, resulting in the reducing of their thicknesses. The GO‐CS improved the hydrophilicity of polyethersulfone (PES) substrate, and their contact angles decreased to 64° with the addition of GO‐CS in the substrate. GO‐CS also increased the porosity of the substrate and surface roughness of FO membrane, thereby optimizing the water flux and reverse salt flux of FO membrane. The average water flux of the FO membrane reached the optimal flux of 21.34 L/(m² h) when GO‐CS addition was 0.5 wt%, and further addition of GO‐CS to the substrate would decrease the water flux of FO membrane, and the reverse salt flux also decreased to the lowest value of 2.26 g/(m² h). However, the salt rejection of the membrane increased from 91.4% to 95.1% when GO‐CS addition increased from 0.5 to 1.0 wt% under FO mode using 1 mol/L sodium chloride (NaCl) solution as draw solution (DS). In addition, high osmotic pressure favored water permeation, and at the same concentration of DS, magnesium chloride (MgCl₂) exhibited better properties than NaCl. These results all suggested that GO‐CS was a good modifier to fabricate FO membrane, and MgCl₂ was a good DS candidate.