二元水溶液在渗透蒸发膜中的传质模型

对二元水溶液在渗透蒸发膜中的传质过程进行了研究,基于Flory Huggins高分子热力学理论和Fujita自由体积理论建立了改进的溶解 扩散模型。在该模型中考虑了组分间相互作用,组分体积分数、温度、膜材料和渗透物特性对传质过程的影响,考察了组分体积分数对相互作用参数的影响,膜材料对水的溶解选择性的影响,原料液组分体积分数、操作温度以及膜厚对渗透通量和分离因子的影响。     

二元醇/水溶液在渗透蒸发均质膜中的扩散模型

用交联聚乙烯酸膜对不同浓度的乙二醇/水溶液在不同温度下分别进行了渗透蒸发实验研究．针对小分子在致密膜中的扩散行为提出了一个新见解,并借用改进的Vigne方程得到了一个新的热力学扩散系数方程,用此方程结合Lee-Thods方程、Wilke-Chang方程、Vrentas和Duda改进的自由体积理论、扩散方程和溶胀平衡方程预测了水和乙二醇分子在不同温度下通过交联聚乙烯醇膜的渗透蒸发行为,其预测结果与实验值基本一致．     

用膜渗透蒸发过程分离乙醇-水混合物的研究

本文报导了用膜渗透蒸发过程进行乙醇-水混合物分离的实验结果。对用CA,CTA,PSf等透水膜分离稀醇水溶液,用PDMS,PVA等透醇膜分离醇-水恒沸物的可行性和经济性进行了初步分析。用基本溶解扩散模型和修正的溶解扩散模型对分离过程的机理作了初步的探讨。     

玻璃态高分子膜中有机溶剂传质行为研究

针对有机溶剂在玻璃态高分子膜中的渗透现象,提出基于物性推算法的膜分离材料选择方法.基于溶解-扩散机理模型,使用统计热力学和状态方程式为基础的GCLF-EOS模型进行溶解度计算、自由体积模型推算扩散系数,同时考虑填充型复合膜的基膜影响,建立膜渗透通量计算模型.本研究充分考虑有机溶剂对高分子的塑化效应,通过引入塑化固子,重新评价对传质过程有效的"空穴自由体积",改进现有的自由体积理论模型.利用芳香族溶剂苯的实验数据和理论预测比较,验证溶解性和扩散性理论模型的正确性.在此基础上对芳香族有机溶剂在玻璃态高分子膜中传递行为进行成功预测.     

渗透蒸发过程脱除水溶液中挥发性有机物的研究

采用自制的PDMS膜研究了从VOCs (挥发性有机化合物 )稀水溶液中脱除VOCs的渗透蒸发过程。以分离因子和渗透通量为评价指标 ,考察了料液浓度、温度和流动状况以及膜下游压力对膜的渗透蒸发分离性能的影响 ;并研究了针对脱除水溶液中VOCs的渗透蒸发过程的传质模型。     

硅橡胶复合膜用于渗透蒸发的膜传质动力学(Ⅰ)膜面上的对流传质

利用自制的硅橡胶平板复合膜对低浓度乙醇水溶液进行渗透蒸发分离乙醇实验 ,研究了过程的传质动力学。基于液 -膜的串联传质阻力模型 ,通过实验测定了膜的总传质系数 ,采用对比差值方法将总传质系数拆分为膜面上的液膜传质系数和膜内的扩散传质系数两部分 ,分析了液相边界层阻力和膜扩散阻力对总传质系数的影响。特别针对膜面上液体流动状况对膜传质的影响进行了探讨 ,得出了液膜传质系数与Reynolds数及温度的关联式。     

膜蒸馏法分离易挥发溶质水溶液

本文以稀甲醇水溶液为实验物系,研究了易挥发溶质水溶液膜蒸馏过程的传质和传热性能。对比直接接触膜蒸馏和空气隙膜蒸馏的实验结果得出,以提浓易挥发溶质为目的的膜蒸馏,采用空气隙膜蒸馏为宜。影响通量的主要因素是空气隙的传质阻力,影响分离因子的主要因素是膜热侧蒸发表面和冷侧冷凝表面之间的温度差。     

水溶液中挥发性有机化合物渗透蒸发分离技术

介绍了水溶液中挥发性有机化合物 (VOCs)的各种分离方法 ,重点分析了渗透蒸发分离技术经济优势。阐释了渗透蒸发膜的选择标准、渗透蒸发过程的传质机理 ,以及原料液浓度、原料液温度、原料液流量、渗透侧压力、添加剂和膜组件型式等因素对渗透蒸发过程分离效率的影响 ,并简要预测了渗透蒸发过程的发展趋势与动态。     

分子筛膜渗透蒸发技术研究进展

概述了渗透蒸发膜分离过程和分子筛膜的优点,重点综述了沸石分子筛膜在渗透蒸发中的传输机理和传质模型,以及温度、压力、组成等对渗透蒸发膜分离性能的影响因素,介绍了分子筛膜渗透蒸发技术在有机溶剂脱水、水中脱除有机物和有机混合物分离等方面的应用,展望了分子筛膜在渗透蒸发膜分离技术中的发展方向。     

渗透蒸发分离稀有机物水溶液

本文在简述了渗透蒸发过程的基本情况后，着重介绍了渗透蒸发分离稀有机物水溶液的进展，对优先透过有机物膜的开发研究及过程参数对膜性能的影响作了系统的综述，最后指出了有机物渗透蒸发良好的应用前景。     

Coupled diffusion of water and ethanol in a polyimide membrane

In this work, the sorplion and steady state permeation of water‐ethanol mixture in an aromatic polyimidc membrane was investigated with the objective of revealing the coupling cherts of water and ethanol in their course of diffusion. The solubility of the watcr‐ethanol mixture in the membrane was determined by means of swelling‐distillation techniques. The sorption behavior was interpreted in terms of the thermodynamic equilibrium equations. The Maxwell‐Stefan mass transfer model was employed as a framework for modeling diffusion. Model equations derived therefrom enable us to cplculate coupled fluxes of water and ethanol from the experimental data. The coupling effects in the diffusion of water and ethanol were revealed by comparing the calculated coupled flux with non‐coupling flux, which was calculated by integration of the Fickian first law using independent diffusion coefficients. Furthermore, the implication of the sole adjustable parameter included in the derived model equations was discussed.     

Continuous dialysis of hydrochloric acid and sodium chloride mixture

Using a two-compartment counter-current dialyzer with single passes, the simultaneous transport of hydrochloric acid and sodium chloride through an anion-exchange membrane Neosepta-AFN was studied at steady state. The diffusion dialysis process was quantified by four membrane mass transfer coefficients, which were correlated with the hydrochloric acid and sodium chloride concentrations in the feed. These characteristics were calculated from the experimental data on dialysis using a two-step procedure combining the numerical integration of the basic differential equations and a multivariable optimization. The second step of this procedure ensured the best agreement between the experimental and calculated data.     

Development of a mathematical model for studying bioethanol–water separation using hydrophilic polyetherimide membrane

An essentially predictive mathematical model was developed to simulate pervaporation process. The group contribution method UNIFAC was used for calculating the upstream activity coefficients. The diffusion coefficient in the membrane was predicted using free‐volume theory. Free‐volume parameters were determined with viscosity and temperature data, and the binary interaction solvent–polymer parameter was calculated by a group‐contribution lattice‐fluid equation of state (GCLF‐EOS). A simulator named PERVAP was developed applying the mathematical model. Pervaporation process was simulated for separating bioethanol–water through polyetherimide membrane. The simulated results were validated using experimental data of bioethanol/water separation through polyetherimide membrane. The model presented a satisfactory performance compared to experimental data. Related to the simulation of the studied separation, a 99% molar enriched bioethanol stream was obtained with a recovery of 94%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

基于多场协同理论的渗透蒸发传质模型

Toprovide a theoretical basis for optimizing the pervaporation procedure, a mass transfer model for pervaporation for binary mixtures was developed basedon the multi-fields synergy theory. This model used the mechanism of sorption-diffusion-desorption and introduced a diffusion coefficient, which was dependent on the feed concentration and temperature. Regarding the strong coupling effect in the mass transfer, the concentration distribution in membrane was predicted using the Flory-Huggins thermodynamic theory. The batch experiments and other experiments with constant composition-were conducted-using a modified chitosan pervaporatioffmembrane to separate tert-butyl alcohol （TBA）-water mixtures. The parameters of the mass transfer model were obtained from the flux of the experiments with a constant composition and the activity coefficients available through phase equilibrium equation, using the Willson equation in the feed side and the Flory-Huggins thermodynamic theory within the membrane The simulation results of the experiments .are in good agreement with the results, of the experiments.     

MODELING ERYTHROMYCIN ADSORPTION TO THE MACROPOROUS RESIN SEPABEAD SP825

We examined the adsorption of aqueous erythromycin (EM) to the macroporous resin Sepabead SP825 in a series of batch experiments. The equilibrium data were well described by a Langmuir isotherm. The free energy, enthalpy, and entropy of adsorption were calculated, and a film and pore diffusion model was used to simulate the mass transfer mechanism, taking into account diffusion across the liquid film surrounding individual particles and diffusion within the resin particle. The model predictions were consistent with the experimental data and consequently were used to determine the mass transfer coefficients.     

Separation of paraffins by membrane extraction combined with crystallization

An integrated mass-exchange process combining liquid-membrane separation with crystallization from solution is experimentally and theoretically investigated. Experiments on separation of binary mixtures of paraffins that have close properties and form mutual solid solutions are carried out. The maximal degree of separation is attained using an aqueous ethanol membrane containing 65 wt % ethanol. From hexadecane-octadecane and hexadecane-tetracosane mixtures containing 86 mol % hexadecane, crystals containing 96.3 and 99.8 mol % hexadecane, respectively, are obtained. The solubility of hexadecane, octadecane, and tetracosane in aqueous ethanol solutions of various concentrations is experimentally studied over a wide temperature range. Using the solubility data, thermodynamic calculations of the liquid-liquid and liquid-crystals equilibria are carried out for the upper and lower boundaries of the aqueous alcohol membrane. A mathematical model of the integrated process is obtained by compiling a set of equations for the diffusion fluxes of the components in the liquid membrane and expressions describing the phase equilibria at the membrane boundaries. A comparison of the experimental data on the separation efficiency with the results of the calculations shows that the diffusion model adequately describes the main features of the integrated process.Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 2, 2005, pp. 120–127.Original Russian Text Copyright © 2005 by Lipatov, Myasnikov, Kulov.     

3种芳香烃在聚乙烯膜中的无限稀释扩散系数

基于Hadj-Romdhane和Danner色谱过程的数学模型 ,采用反相气相色谱法在 348.2～ 36 3.2K温度范围内测定了苯、甲苯和乙苯 3种芳香烃溶剂在聚乙烯膜中的无限稀释扩散系数 .实测数据的关联结果表明 ,采用空穴自由体积替代Vrentas-Duda自由体积理论方程中自由体积项的修正方程 ,能很好地描述溶剂分子的无限稀释扩散系数随温度的变化关系 .同时在修正方程的基础上建立了一般化自由体积方程 ,并对该方程的预测能力进行了探讨     

有机分子在聚乙烯膜中扩散过程的分子动力学模拟

引言聚乙烯(PE)是由乙烯单体聚合而成的相对分子质量较高的线性烷烃,是合成树脂中应用最广泛的品种。扩散系数是描述传递现象的基本物性参数,在聚合物材料开发方面具有重要的理论特性和广阔的应用前景。用实验方法测定扩散系数时,操