Concentration Profiles in Hollow-Fiber Dialyzers

Abstract

Concentration profiles in hollow-fiber dialyzers have been determined experimentally by the use of a hollow fiber dialysis cascade employing aqueous salt and urea solutions. A mathematical model has also been developed to predict radial and axial concentration profiles for co-and counter-current operation. The experimental and predicted results are compared.     

溶胶修饰陶瓷膜的气体渗透

本文用纯氮气、氢气及氮氢混合气以静态法和流动法分别研究了自研制的复合不对称陶瓷膜的气体渗透性能，并获得了较适宜的涂膜次数及尖透工条件（温度、压差）对膜渗透性能的变化规律。作者对氮氢混俣气流动体系中混合气流速、组成及吹扫气量对渗透性能的影响也进行了详细研究。     

Prediction of Membrane Thickness in Hydrocarbon Permeation through Liquid Surfactant Membrane

Abstract

Separation of a mixture of toluene and heptane by means of a liquid surfactant membrane was studied. With the help of a membrane film model for mass transfer through a liquid membrane, the validity of the assumption made by Casamatta et al. in their study of hydrocarbon separation through a liquid water membrane was determined. This paper also proposes a novel method to determine the exact thickness of the liquid membrane through which permeation takes place, and thus eliminates any possibility of underprediction of the extraction rate as is made by other investigators considering the maximum membrane thickness.     

Emulsion Prevention with Supported Liquid Membrane Permeation

The urge to achieve climate protection goals and a more prevalent interest in finding alternatives to fossil fuel‐based products focus attention increasingly on cascade raw material utilization, respectively, to intensify commercial production processes. The present project provides a study on the combination of liquid‐liquid extraction and esterification using the system acetic acid/octanol and 4‐dodecylbenzenesulfonic acid as catalyst. The surfactant 4‐dodecylbenzenesulfonic acid causes emulsification during extraction, but emulsification was successfully avoided by using supported liquid membrane permeation equipment.     

Inversion of Selectivity in the Liquid Membrane Permeation Process

Abstract

The dependence on different operative techniques of the separation factor obtained through liquid membrane permeation process is studied. An interpretation of inversion of selectivity is proposed by taking into account the different configurations of the liquid membranes.     

内置钝体对快速流化床中颗粒浓度分布的影响

本文在内径140mm的快速流化床中,考察了内置钝体对床内轴向压力分布和径向颗粒浓度分布的影响。实验结果表明,内置钝体构件对于快速流化床中的压力和浓度的分布影响显著,而且大大增强了气固两相的径向混合。     

Preparation of Palladium-Silica Conjugated Membrane for Selective Hydrogen Permeation

Palladium membranes were prepared on an a-alumina support by metal-organic compound chemical vapor deposition (MOCVD) method from palladium(Ⅱ) acetate precursor. Permeation properties of hydrogen and helium gas were studied as a function of the number of times of deposition of palladium on the peeling off phenomenon of palladium, which is common in electroless plated membrane, was observed. Silica was introduced into the pores to prevent the palladium grain from peeling off. The palladium-silica conjugated membrane does not show the peeling off phenomenon and can withstand the high temperature up to 800CCCC which is the upper limit of our apparatus. The separation factor for hydrogen gas over carbon dioxide gas was improved with the increase of number of times of silica coating by sacrificing the H2 permeation and finally increased to four times. The improvement on the separation of hydrogen gas over carbon dioxide for palladium-silica conjugated membrane was evaluated and a model of permeation pattern     

Pd-SiO2复合膜的氢气选择渗透特性

Palladium membranes were prepared on an a-alumina support by metal-organic compound chemical vapor deposition (MOCVD) method from palladium(Ⅲ) acetate precursor. Permeation properties of hydrogen and helium gas were studied as a function of the number of times of deposition of palladium on the peeling off phenomenon of palladium, which is common in electroless plated membrane, was observed. Silica was introduced into the pores to prevent the palladium grain from peeling off. The palladium-silica conjugated membrane does not show the peeling off phenomenon and can withstand the high temperature up to 800℃ which is the upper limit of our apparatus.The separation factor for hydrogen gas over carbon dioxide gas was improved with the increase of number of times of silica coating by sacrificing the H2 permeation and finally increased to four times. The improvement on the separation of hydrogen gas over carbon dioxide for pulladium-silica conjugated membrane was evaluated and a model of permeation pattern (palladium and silica) was proposed. This model suggests that the separation factor for hydrogen over carbon dioxide could be improved by introducing silica layer because the silica layer fills the pores and reduces the gas permeation without sacrificing the hydrogen permeation through the palladium region. These results indicate that the introduction of silica into the palladium grain is a promising means to improve the hydrogen separation performance of palladium based composite membranes.     

钙钛矿型致密膜透氧过程的应用研究

对钙钛矿型致密膜的透氧过程进行了实验研究,验证了所建数学模型的正确性,并对数学模型中的材料参数、应用范围、模型对厚度的敏感性及模型在极限条件下的适用性等进行了分析研究,力图实现以模型为手段,优化实验操作条件,用模型来预测不同工艺条件对膜透氧速率的影响,减少探索性实验的工作量,进而为实现其工业化应用提供指导。     

Elemental Concentration Profiles in an Oxidized Silicon Nitride Material

Secondary ion mass spectrometry (SIMS) has been used to characterize elemental concentration profiles which build up within and below the oxide scale on a Si₃N₄ material during oxidation. By in-depth profiling it was shown that the oxide scale had a high concentration of cations originating from the intergranular regions of the material. The subscalar region contained a zone depleted in these elements, and the width of this zone was dependent upon the particular element. Prolonged oxidation at elevated temperatures appeared to level out the initially formed concentration profiles.     

Modeling of the Permeation of Thorium through Liquid Emulsion Membrane

Abstract

A general permeation model for the separation of thorium by liquid emulsion membrane (LEM), using theonyletrichloroacetone HTTA as a carrier is presented. The internal mass transfer in the W/O emulsion drop, the external mass transfer around the drop, the rates of formation, and the decomposition of the complex at the external aqueous‐organic interface were considered. Further, the leakage of the internal aqueous phase to the external phase due to the membrane break‐up is also taken into account. The batch extraction of thorium using HTTA as a carrier was carried out under various experimental conditions. It is found that the extraction rates can be satisfactorily simulated by the proposed model.     

聚偏氟乙烯微孔膜的制备与透过性能研究

采用相转化法制备聚偏氟乙烯（PVDF）微孔膜,研究了铸膜液中聚偏氟乙烯含量、溶剂的种类、添加剂的种类和含量、膜厚度以及操作压力等因素对聚偏氟乙烯膜水通量的影响,采用扫描电子显微镜观测了制备膜的表面结构。结果表明,制膜条件对聚偏氟乙烯微孔膜通量有重要影响,通量随添加剂含量和压力的增大而增大,随PVDF含量和膜厚度的增大而减小;当压力上升到0．16MPa时,通量将不随压力变化,达到极限通量。     

亚砜基改性纤维素膜的SO2气体渗透性能研究

分别使用二甲基亚砜浸泡的物理方法及苯基乙烯基亚砜加成的化学方法对纤维素膜进行了改性,并对改性膜的性能进行了测试.结果表明改性后纤维素膜仍为致密结构,SO2的渗透性能及其对N2的分离性能明显提高,其中改性液中添加二甲基亚砜的均相化学加成反应所得的改性膜具有较好的SO2渗透稳定性.     

Effects of Membrane Parameters on Performance of Vapor Permeation through a Composite Supported Liquid Membrane

Abstract

Support liquid membranes have been used in air dehumidification due to their inherent high mass transfer rates. In this study, the effects of membrane structural parameters on vapor permeation through a LiCl solution based supported liquid membrane are investigated. To aid in the analysis, a mass transfer model has been proposed for moisture transfer through the membrane, which is composed of a supported liquid layer sandwiched by two hydrophobic protective layers. The model takes into account of the resistance in boundary layers, in the protective hydrophobic layers, and in the supported liquid layer. It is a transient model. It also reflects the distributed nature of moisture permeation through the membrane. The results found that the emission rate exhibits a non‐uniform distribution nature on the membrane surface. The structural parameters of the support and the protective layers, such as thickness, pore diameters, and porosity, have great effects on vapor permeation.     

膜法明胶浓缩技术在明胶工业化大生产中降低灰分的研究

本文研究了在明胶工业化大生产中应用膜法明胶浓缩设备降低明胶产品的灰分。结果发现,膜法明胶浓缩设备在对明胶稀胶液浓缩的同时,一般可以将明胶中的灰分降低到1.0%以下。同时,本文从理论和实践两个方面论证了膜法明胶浓缩设备运行方式不同,降低灰分的程度也会不同。在相同条件下,连续浓缩模式对灰分的去除率总是高于循环浓缩模式。本文首次发现,二者间存在严格的定量关系。和传统的离子交换技术相比,膜法明胶浓缩技术在降低明胶灰分上更具有成本优势和竞争力。采用连续浓缩模式运行的膜法明胶浓缩设备对原始灰分为1.5%～3%的明胶,完全可以替代离子交换技术用于明胶去除灰分。对高灰分的明胶(例如,4%～5%),从理论上讲,只要增加设备系统的级数,亦能替代离子交换技术,使明胶灰分降至1.0%以下。本文依据大批工业化大生产中的实验数据,首次揭示了膜法明胶浓缩设备降低明胶灰分的规律及实际效果。     

PTFE多孔膜气体渗透数学模型和膜孔结构的影响

Membrane-based separation processes are new technology combined membrane separation with conventional separation. Hydrophobic porous membranes are often used in these processes. The structure of hydrophobic porous membrane has significant effect on mass transfer process. The permeabilities of five kinds of gas, He, N2,O2, CO2 and water vapor, across six polytetrafluoroethylene(PTFE) fiat membranes were tested experimentally.Results indicated that the greater the membrane mean pore size and the wider the pore size distribution are, the higher the gas permeability. A gas permeation model, including the effects of membrane structure parameter and gas properties, was established. A comprehensive characteristic parameter (including porosity, thickness and tortuosity) was found more effective to express the influence of membrane structure in gas permeation process. The predicted permeation coefficients were in good agreement with experimental data.     

Germanium Recovery using Catechol Complexation and Permeation through an Anion-Exchange Membrane

Germanium in solution was recovered on an anion-exchange membrane after complexation with 3-methylcatechol. The complex was transferred to the anion-exchange membrane by convection, which meant diffusion was not the rate-determining step as in conventional resin recovery. In batch mode, the optimum solution pH was 8, and at this pH the method was selective for germanium against silicate ion. In continuous mode at pH 11.0 and 2.0, the germanium ion was selectively adsorbed as a complex ion in the membrane. This system could be applied to hydrometallurgy processes for the recovery of germanium.     

高聚物/陶瓷复合膜的气体渗透及分离行为

以实验室制备成功的SR／Ceramic和PPESK／Ceramic复合膜为基础,对O2、N2、H2、CO、CO2、CH4等气体在高聚物／陶瓷复合膜上的渗透性能进行研究;在较宽的温度范围内考察了复合膜的使用效果,并获得各种气体的渗透活化能及其与气体临界温度的关系;渗透活化能随临界温度的增大而增低。同时,以空气分离体系为对象,考察了膜分离器的操作参数q和pr对膜分离系统过程行为的影响;实验结果和理论分析一致。