Coupled Phenomena Membrane Distillation and Osmotic Distillation through a Porous Hydrophobic Membrane

Abstract

Water transport in the vapor phase through a porous hydrophobic membrane has been studied in different experimental situations. Pure water and/or different aqueous solutions of sodium chloride, ranging from 0.5 to 5 mol/L, were employed on both sides of the membrane. The experiments were carried out under temperature differences varying between 5 and 30 K, and at mean temperatures varying between 20 and 40[ddot]C. The stirring rate was varied between 0 and 350 rpm. The results were interpreted based on the existence of unstirred polarization layers.     

Purification of Radioactive Wastes by Low Temperature Evaporation (Membrane Distillation)

Abstract

A method of radioactive waste concentration by membrane distillation is presented. Water flow through a hydrophobic membrane results from the temperature gradient between membrane surfaces which are in contact with two waste streams, warm and cold. A transport of water from the warm to the cold stream occurs and radionuclides and other impurities are concentrated in the warm stream (retentate).     

Estimation of Mass Transfer Rates through Hydrophobic Pervaporation Membranes

Abstract

In pervaporation of dilute solutions (acids, esters, and ketones) through hydrophobic membranes, mass transfer coefficients increased with temperature in an Arrhenius-like manner. Activation energies and pre-exponential factors were estimated through empirical correlations, allowing estimation of mass transfer coefficients. The activation energy was a function of the heat of sorption and the elastic modulus of the membrane. For low molecular weight compounds, the heat of sorption was the more important of these two factors, whereas the membrane thickness (which influenced the elastic modulus) became more important for larger compounds. The compensation effect allowed pre-exponential factors to be estimated from the activation energies.     

低温多效蒸发海水淡化系统性能的实验研究

针对大型海水淡化工程设计关键技术,依托1 t·d-1低温多效蒸发海水淡化实验平台,考察了装置运行性能的稳定性,系统地研究了不同海水进料量及首效蒸汽温度对造水比、浓缩比和产品水质等关键参数的影响。结果表明:在实验条件范围内,随着首效蒸汽温度提高,海水的浓缩比先减小后增加,而首效温度对造水比的影响较小;在一定首效温度下,浓缩比随着海水进料量的增大而减小,而造水比随海水进料量的增大而增大。在实验范围内,产品水的固体总溶解浓度均低于5 ppm。小型海水淡化平台关键技术的实验研究为低温多效海水淡化系统在扩大化中的设计优化提供了参考和借鉴。     

膜蒸馏用多孔陶瓷膜的疏水改性

膜蒸馏海水淡化是一种从源头上获得淡水资源的技术,是解决水资源紧缺的一种 重要途径。膜蒸馏需要的膜材料为多孔疏水膜,而陶瓷膜一般具有亲水性,所以陶瓷膜的疏水 改性是决定其在膜蒸馏中应用的关键。传统的疏水改性方法包括接枝聚合、仿生微纳结构构筑、 溶胶-凝胶、化学气相沉积、聚合物沉积等,改性后的疏水或者超疏水陶瓷膜已经被应用于膜蒸 馏海水淡化,但是长时间稳定性的不足阻碍了其实际工业应用。最近我们提出了一种有效的通 过聚合物热解对陶瓷膜进行疏水改性的方法,可以获得具有高热稳定性、化学稳定性、抗腐蚀、 抗冲击的疏水陶瓷膜,具有优异的长时间稳定性能,可获得稳定的淡水产出。本文将介绍各种 陶瓷膜疏水改性方法,阐述几种方法的优缺点,并且探讨他们在膜蒸馏海水淡化中的工业应用 潜力。     

Nonisothermal Water Transport through Hydrophobic Membranes in a Stirred Cell

Abstract

This paper studies the transport of pure water through microporous hydrophobic membranes in a stirred cell when bathed by two phases at different temperatures. The dependence of the phenomena on the stirring rate and on the average temperature has been investigated. The influence of these operating conditions on the mass transfer rate is discussed while keeping in mind the theories of mass and heat transfer within the membrane and adjoining liquids. The concept of temperature polarization is introduced in the transport equations, and it is shown to be important in the interpretation of our experimental results.     

Vapor Phase Fabrication of Hydrophilic and Hydrophobic Asymmetric Polymer Membranes

The fabrication of asymmetric polymer membranes via vapor phase deposition is demonstrated. In this solventless process, the dense layer is deposited first and then the porous layer is subsequently deposited onto the dense layer. A variety of functional polymer membranes can be produced by varying the precursor molecules. The functionality of the dense and porous layers can be independently tailored to be either hydrophobic or hydrophilic, resulting in membranes that are fully hydrophilic, fully hydrophobic, or asymmetric in both structure and chemical functionality. The thickness of both the porous and dense layers can be separately tuned by controlling the deposition time.

     

疏水微孔膜在膜分离过程中的应用

根据文献报道和作者的工作实践,介绍了疏水微孔膜的主要制备方法,并对膜蒸馏等一些采用疏水微孔膜的新型膜分离过程进行了评述。     

膜材料的亲疏水性对固定化脂肪酶的影响

用吸附法固定脂肪酶时,膜材料的亲疏水性对固定化酶的量、比活力和活力稳定性等有很大影响.今以柱状假丝酵母脂肪酶和猪胰脂肪酶为研究对象,选取了8种亲疏水性不同的膜材料(醋酸纤维素、聚丙烯腈、聚酰胺、聚砜、聚醚砜、聚偏二氟乙烯、聚丙烯和聚四氟乙烯)作为固定化载体,用吸附法制备了固定化脂肪酶膜.研究结果表明,强疏水性聚四氟乙烯和聚丙烯膜对两种酶的吸附量都比较大,且固定化酶的比活力和活力回收率比较高,聚四氟乙烯固定化柱状假丝酵母酶比游离态酶的半衰期提高了6倍以上.强亲水性醋酸纤维素膜对猪胰脂肪酶的吸附量比聚四氟乙烯高,但是固定化酶的比活力、活力回收率比强疏水性膜低,而接触角在40°～50°的聚酰胺膜和聚砜膜的吸附量最小.因此吸附法制备固定化脂肪酶膜,选择聚丙烯膜和聚四氟乙烯膜是合适的,制备的优化条件为吸附温度25℃,酶溶液的pH为7.5,吸附时间10 h.     

气体在均质高分子膜中渗透过程的研究

本文研究了气体在玻璃态聚合物膜中的渗透行为,提出了Langmuir环境和Henry环境的渗透分离系数的概念,推导出它们与表观分离系数间的关系,分析了压力,组成和温度及膜的玻璃化转变对选择渗透性的影响,验证了双吸着双迁移模型及其扩展形式的适用性.通过理论分析和实验证明探讨了实际中出现的“快气变慢,慢气变快”及“纯气渗透系数之比往往高于实际的混合气渗透分离系数”,指出其并非一般性结论,有时会出现与此相反的结果.     

Mass Transport Through PDMS/Clay Nanocomposite Membranes

Poly(dimethylsiloxane)/clay nanocomposite membranes have been synthesized and mass transport properties through those nanocomposite membranes have been investigated. The effect of mechanical deformation on the transport properties of the PDMS (nanocomposite) membranes has also been studied. With the introduction of clay particles into the polymer matrix, mass transport is reduced, likely due to the longer diffusion path, which slows the diffusion process. The effect of membrane extension on diffusion is more complicated. Under small deformation, the permeation flux decreases, but under high deformation, it shows an enhanced diffusion. As the clay particle concentration increased, the effect of external deformation is reduced, and an enhanced diffusion is observed.     

有机涂层在低温多效蒸馏海水淡化装置中的应用前景

介绍了海水淡化技术的现状及主流技术,阐述了有机涂层作为新技术和新工艺在低温多效蒸馏海水淡化装置中的应用前景。     

影响煤的格金低温干馏试验数据准确性的探讨

针对煤的格金低温干馏试验,在明确试验特征及其结果准确性重要意义的基础上,对试验结果准确性主要影响因素与处理方法进行分析,并采用定量的方式验证处理方法可行性与有效性。     

Transport Behavior of Electrolytes Through Charged Mosaic Composite Membranes

The first part of this article reviews the strong acid/strong base type charged mosaic composite membrane. A template pattern with alternating poly(4-vinylpvridine) (P4VP)/poly(vinyl alcohol) (PVA) lamellae was fabricated upon a microporous membrane by casting of poly[4-vinylpyridine (4VP)-g-vinyl alcohol (VA)] graft copolymer from a water/l-propanol mixture. After a treatment involving the binding of the microporous membrane with the graft copolymer and also domain fixing of the PVA phases, a dilute solution of poly[sodium p-styrenesulfonate (SSS)-g-VA] graft co-polymer/P4VP binary blend was cast on this template surface. After chemical treatments (introduction of a positive charge and domain fixing of ion-exchange regions), we examined the transport of KCl and selective transport of a KCl-sucrose mixture through the charged mosaic composite membrane. The second section reviews the weak acid strong base type charged mosaic composite membrane. In this type, the charged mosaic regions were composed of poly(acrylic acid) (PAA) and quaternized P4VP microdomains. The microstructure of binary blend was observed from scanning electron microscopy (SEM) by wet-etching of films after domain fixing of one component of the binary blend. We examined the transport of KCl and L-phenylalanine through the charged mosaic composite membranes.     

CO2通过合成聚合物膜的促进传递

Two kinds of fixed carrier membrane materials containing secondary amine and carboxyl groups which can be used as carriers of CO2 were prepared. One was poly(N-vinyl-7-sodium aminobutyrate)(PVSA), which was obtained through the hydrolysis of polyvinylpyrrolidone (PVP) synthesized with N-vinylpyrrolidone(NVP) by radical polymerization. The other was poly(N-vinyl-7-sodium aminobutyrate-co-sodium acrylate)(VSA-SA), which was obtained through the hydrolysis of copolymer of N-vinylpyrrolidone and acrylamide(AAm) (NVP-AAm). The composite membranes were developed with PVSA or VSA-SA as active layer and polysulfone (PS) as support membranes. The permeation rates of pure CO2 and CH4 gas as well as binary mixtures of CO2/CH4 through the composite membranes were measured. The results show that the composite membranes present better CO2 permeation rates than other fixed carrier membranes do reported in literature. For example, at 26℃, 1330 Pa of CO2 pressure, the PVSA/PS composite membrane displays a CO2 permeation     

Hydrophobic Modification and Regeneration of Shirasu Porous Glass Membranes on Membrane Emulsification Performance

The effect of hydrophobic modification and regeneration of Shirasu porous glass (SPG) membranes was systematically investigated on the monodispersity of emulsions. The results showed that the hydrophobic modification and regeneration of SPG membranes had little influence on the monodispersity of emulsions, no matter how many modification and regeneration runs were operated. The emulsification runs affected the emulsification performance to a certain extent when hydrophobically‐modified SPG membranes were used for preparing water‐in‐oil (W/O) emulsions repeatedly. However, they almost did not affect the emulsification performance when regenerated hydrophilic SPG membranes were used for preparing oil‐in‐water (O/W) emulsions. The SPG membranes could be used repeatedly after hydrophobic modification or regeneration with almost the same emulsification performance as fresh or freshly‐modified ones. The results provided some valuable guidance for the repetitive use of SPG membranes to prepare monodisperse O/W and W/O emulsions.     

疏水性SiO2-PDMS渗透汽化膜溶解-扩散性能

制备了疏水性纳米SiO2填充聚二甲基硅氧烷(PDMS)渗透汽化膜,研究了其溶解-扩散性能,计算了复合膜的溶解度参数(δM)及乙醇渗透系数(PE)。结果表明,填加SiO2提高了PDMS膜的乙醇溶解度(SE),SiO2填加量为10%(质量分数,下同)时,复合膜在30℃时的SE为0.0064,而未填加时仅为0.0026;PE值随SiO2含量的增加呈先增加后减小的趋势,SiO2填加量5%时,PE在60℃时为2.52×10-13 m2/s,而未填加时仅为1.42×10-13 m2/s;提高温度有利于乙醇的渗透。以乙醇/水物系为研究对象,结果表明,SiO2-PDMS复合膜渗透汽化性能与其渗透系数的变化趋势基本相同。     

低温压力容器及低温低应力容器的设计

目前压力容器主要应用于石油化工、低温工程以及制冷设备中。其中低温压力容器的应用比重较大。基于此,首先对压力容器的基本定义进行阐述,然后对其设计过程中的具体思想进行分析。主要对低温压力容器容易出现脆裂的问题进行着重分析,并对低温压力容器的设计温度、选材以及结构优化方面进行研究,从而低温压力容器的安全性得到提高。     

印尼INDRAMAYU电厂4500t／d低温多效海淡装置介绍

本文对印度尼西亚INDRAMAYU火电厂4500t／d低温多效海水淡化装置的基本参数、技术特点、经济效益和主要制造工序等进行了简要的介绍。该装置是中国首台出口到国外的大型低温多效海水淡化装置,无论装置规模或制造难度上都开创了先例。     

低温等离子体聚合反应

简述了低曙等离子体聚合反应的基本特征,类型,反应机理及其在聚合物材料改性方面的应用前景。