有机液优先透过渗透汽化膜

有机液优先透过膜作为渗透汽化膜及其相关过程的重要组成部分,近年来受到高度关注。综述了近年来有关其膜材质结构－分离特性,以及用于有机液／水分离研究的进展。     

有机物优先透过的聚二甲基硅氧烷渗透汽化膜的改性研究进展

有机物优先透过的渗透汽化过程(Organophilic Pervaporation,O-PV)是一种膜分离技术,可以有效脱除化学、制药、电子、石化、印刷、涂料、纺织等工业废水中含有的微量挥发性有机物(Volatile organic compounds,VOCs),如苯、甲苯、三氯乙烯、氯仿和苯酚等.膜(一般指高分子膜)是O-PV过程的核心,而用于O-PV的膜分离性能主要取决于膜材料所具有的内在分离性能.聚二甲基硅氧烷(Poly(dimethyl siloxane), PDMS )是目前为止应用最为广泛的O-PV膜材料.本文综述了有机物优先透过的PDMS渗透汽化膜的改性研究进展,并展望了其未来的发展方向和前景.     

用脉冲梯度场核磁共振技术研究乙醇-水混合液在壳聚糖渗透汽化膜中的自扩散过程

用脉冲梯度场核磁共振技术(PFG—NMR)研究了水、乙醇和乙醇一水混合液在硫酸交联的壳聚糖渗透汽化膜和未交联的壳聚糖渗透汽化膜中的自扩散过程,得到了乙醇和水的溶解度和自扩散系数,阐述了水和乙醇透过壳聚糖膜的机理;实验结果表明：水和乙醇是分别由两种不同类型的扩散通道透过膜的;水是由亲水性的离子化通道扩散透过膜,而乙醇是由亲油性的高分子无定形区扩散透过膜;PFG—NMR方法所得到的结果与渗透汽化实验所得到的结果完全一致。     

渗透汽化复合膜*

渗透汽化是膜科学研究中最活跃的领域之一,在分离液体混合物,尤其是痕量、微量物质的移除,近、共沸物质的分离等方面有独特优势。介绍了渗透汽化膜的种类和复合膜的制备方法。按渗透汽化三大分离体系,即从水相中分离有机物、有机液脱水和有机混合液的分离,综述了近几年渗透汽化复合膜的研究进展。最后,指出了制约其发展的问题和未来发展方向,并对渗透汽化复合膜的应用前景进行了展望。     

MOF-聚合物混合基质膜的制备、改性及其在渗透汽化中的应用

渗透汽化是一种具有能耗低、操作简便等优点的膜分离技术,目前传统聚合物渗透汽化膜在分离性能和稳定性等方面还有欠缺。金属有机框架(MOF)是由金属离子与有机配体以自组装形式组建而成的晶态多孔材料,具有独特的性质,如对目标分子的选择性吸附和分子筛分效应,近年来许多研究表明将MOF作为填料引入聚合物基质中构筑混合基质膜(MMMs)对其渗透汽化性能有很好的促进作用。本文从MOF的不同系列出发,讨论了适用于渗透汽化混合基质膜的MOF种类,分析了MOF-聚合物混合基质膜的制备方法与改性策略,综述了该类混合基质膜在渗透汽化方面(有机溶剂脱水、从稀溶液中回收有机物、有机混合物的分离)的应用进展,总结了用于渗透汽化的MOF-聚合物混合基质膜研究面临的挑战,并对其未来发展提出展望。     

聚1-三甲基硅基丙炔膜渗透汽化分离乙醇-水溶液的研究Ⅰ.PTMSP膜渗透汽化分离乙醇-水传质的基本特征

研究了聚１－三甲基硅基丙炔膜渗透汽化分离乙醇－水溶液传质的主要特点。发现膜对乙醇优先吸附、溶解，对水优先扩散。但因吸附液中水含量很低，总的结果表现为优先透醇。在３１３Ｋ，膜厚２０～２５μｍ，料液浓度１０ｗｔ％时，α＝１８．５，Ｊ＝０．９６９ｋｇ·ｍ－２·ｈ－１。透过膜的渗透液及其中的水和乙醇渗透汽化表观活化能分别为２８．８７、３１．３０和２７．６６ｋＪ／ｍｏｌ，并随料液浓度下降而增加。对实验数据进行非线性回归，建立了该膜传递乙醇的经验关联式：Ｊｅ＝－５．５６４Ｃ２Ｅ０＋１３．３４ＣＥ０－０．１５７３（ｋｇ·ｍ－２·ｈ－１），计算值与实验值相吻合。     

渗透汽化膜分离研究的新进展

渗透汽化膜分离技术是当前分离膜研究领域的前沿课题之一.作为化学分离中的重要组成部分,近年来受到高度重视.本文按渗透汽化膜分离的三大类混合液体系有机液脱水、从水相中分离有机物和有机混合液的分离,综述了近几年渗透汽化膜分离技术研究的新进展.其中,又重点报道了有机混合液分离的最新研究成果,将其分为:极性/非极性化合物、芳香烃/脂肪烃体系、芳香烃/脂环烃体系、同分异构体、多元体系和汽油脱硫等六部分进行了详细叙述.文章最后还对渗透汽化膜分离研究进行了展望.     

渗透汽化优先透醇分离膜

20世纪70年代的能源危机促使了人们对可再生能源-发酵法制备乙醇与节能分离工艺的探求。渗透汽化膜分离技术作为一种新兴的膜分离技术,具有分离效率高、低能耗、易于和发酵装置耦合、易于与其它分离方法联用等显著优点,特别适用于乙醇/水等恒沸混合物体系的分离。本文简要介绍了渗透汽化优先透醇膜的研究背景,总结并分析了用于指导膜材料选择的理论,详细介绍了用于制备优先透醇膜的含硅聚合物、含氟聚合物、有机/无机复合膜材料以及其他聚合物等膜材料的的结构特点、改性方法及膜材料分子结构与渗透汽化性能间的关系,并对不同膜材料对乙醇/水的渗透汽化分离性能进行了总结比较,在此基础上总结了目前渗透汽化乙醇/水分离膜存在的问题,并对其未来的研究方向和发展前景进行了展望。     

用聚电解质渗透汽化膜进行乙醇脱水

渗透汽化 (PV)膜过程由于可用于有机 /有机及有机 /水的恒沸或近沸混合物的分离而成为近年来膜技术研究开发的热点[1,2 ] .德国 GFT公司所制的富马酸交联 PVA脱水膜[3] 对温度为 80℃的 80 %Et OH料液 ,其分离因子为 350 ,渗透通量为 2 0 0 g/ (m2 ·h) .优秀的分离膜要求渗透通量大 ,同时具有较高的分离因子和良好的稳定性 .因此 ,提高膜的分离性能是渗透汽化技术开发应用的关键 .周继青等 [4 ]研究了 PVA/ PVP互穿网络膜的渗透汽化性能 ,发现膜的渗透通量虽有明显提高 ,但膜的选择性下降 .聚电解质具有优良的亲水性 ,可制得高水通…     

醇／水混合液分离用聚乙烯醇复合膜的渗透汽化特性

制备了聚乙烯醇（ＰＶＡ）／聚丙烯睛（ＰＡＮ）渗透汽化复合膜，研究了交联剂用量、底膜结构、进料液组成、操作温度等因素对膜的渗透汽化性能的影响．发现ＰＶＡ／ＰＡＮ复合膜对水／醇混合液表现为水优先透过，进料液中乙醇浓度在６０～９９ｗｔ％的范围内，渗透通量Ｊｔ与温度之间符合Ａｒｒｈｅｎｉｕｓ关系，选择分离系数αＷ／Ｅ也随温度上升而增大．进料液为９５ｗｔ％的乙醇／水混合液时，７５℃下Ｊｔ高达３００～４５０ｇ／ｍ２ｈ，αＷ／Ｅ为８００～１１００．对异丙醇／水、异丁醇／水及甘油／水混合体系，复合膜显示出更为优秀的透过、分离性能．就膜的化学、物理结构与其渗透汽化性能间的关系进行了讨论．     

渗透汽化分离芳烃/烷烃混合体系的研究进展*

本文对近年来应用于分离芳香烃/ 烷烃混合体系的渗透汽化(简称PV ) 膜材料, 特别是高分子材料进行了较为系统的综述, 并简要概述了渗透汽化膜分离特点、机制以及影响渗透汽化分离过程的主要因素。     

Water-alcohol Separation by Pervaporation through Zeolite Modified Poly(amidesulfonamide)s (PASAs)

A series of poly(amidesulfonamide)s (PASAs) which have been synthesized in our laboratory possess good membrane fabrication properties^[1]. The potential use of these membrane materials in RO, UF and PV were demonstrated^[2,3]. Reminiscent to the PV performance of other glassy polymers, most of these materials exhibit a fairly high separation factor albeit a permeation flux below 35 g m^-2 h^-1 in the PV separation of aqueous alcohol mixtures. To have a real application prospect in PV, the permeation flux through the membranes has to e further improved. The present work represents our effort to upgrade the separation characteristics of PASAs by blending with inert hydrophilic zeolites. Three types of PASAs (structure shown in Figure 1) were selected to be fabricated by blending different amount of zeolite NaA or NaX. The zeolite filled membranes were characterized by SEM, IR spectroscopy, sorption measurements and wide-angle X-ray diffraction. By adding proper amount of NaA into the polymer casting solutions, the resultant zeolite filled membranes exhibited improvement in both selectivity and permeability in the separation of 10% aqueous solutions of ethanol, propan-l-ol and propan-2-ol, as compared to the zeolite free membrane (Table 1).     

渗透汽化芳烃/烷烃分离膜材料

芳烃/烷烃混合物的分离在石油化工及环保领域都具有重大意义.与传统的萃取精馏等技术相比,渗透汽化膜技术以其清洁、节能和高效的优点,应用于芳烃/烷烃混合物的分离并受到重视.本文综述了渗透汽化芳烃/烷烃分离膜的研究进展,概述了渗透汽化技术的基本原理和应用,重点介绍了用于渗透汽化芳烃/烷烃分离的聚酰亚胺、聚氨酯等高分子膜材料的结构特点和分离性能.总结了膜材料的接枝、共聚和共混,添加传质促进剂的改性方法.分析了渗透汽化芳烃,烷烃分离膜材料的研究思路,在此基础上对渗透汽化芳烃/烷烃分离膜材料的研究方向和发展前景进行了展望.     

改性超滤膜技术在水处理中的应用研究进展

膜技术由于其兼具较好的处理效果和较小的环境影响的特点,在水处理领域的应用前景广阔,其中超滤膜因其抗污染能力强、使用寿命长的特点广泛应用于水处理中。本文针对不同的应用场景总结梳理了聚偏氟乙烯超滤膜、TiO₂管式复合超滤膜、聚醚砜超滤膜这三种常见的超滤膜材料的改性方法和改性膜特点,讨论了这些改性膜材料在水处理过程中的应用现状和亟需解决的问题,以期为膜处理技术中的发展和应用提供科学支撑和理论依据。     

Evaluation of the dehydration performance of zeolite NaA membrane on porous alumina tube by the alumina X-ray diffraction intensity.

A zeolite NaA (A-type zeolite of ca. 0.4 nm pore size; Linde Type A, LTA) membrane for the dehydration of alcohol was characterized by X-ray diffraction analysis (XRD). Also, the relationship between the X-ray absorption and the EtOH/H2O pervaporation (PV) dehydration performance (water selectivity and permeation flux) of the LTA membrane was first investigated. The LTA membranes used here were gel-synthesized hydrothermally on an alumina porous support tube. Since diffraction lines from the alumina generate from a deeper layer than those of the LTA crystal, and are absorbed by both the surface LTA crystal and materials embedded in the alumina porous support, the alumina (113) diffraction line was intensively monitored to estimate the overall X-ray absorption by the LTA membrane. The intensity of the alumina (113) diffraction line showed a good correlation with the PV dehydration performance of the LTA membrane, that is, lower values with the water selectivity and higher values with the permeation flux. The lower diffraction intensity means stronger X-ray absorption by the LTA membrane. The major factor causing the difference in the X-ray absorption is the thickness or quantity of materials embedded in an alumina porous support, rather than those of the surface LTA crystal. These phenomena can be used conveniently (without real PV experiments) to determine the EtOH/H2O PV dehydration performance of the LTA membrane.     

Recent advances in sodium alginate-based membranes for dehydration of aqueous ethanol through pervaporation

Sodium alginate (SA) is a progressive material for membrane fabrication. The technological development of SA-based membranes has made a significant contribution to the separation techniques, especially in aqueous organic solutions. The outstanding performance of SA is attributed to its outstanding structural flexibility and hydrophilicity. In view of structural characteristics, SA membranes have immense utilization in the pervaporation separation of organics. Among various organics, dehydration of aqueous ethanol is employed as a standard to check the success of pervaporation (PV) membrane. Because ethanol and water have comparable molecular sizes, thus difficult to extract water from aqueous ethanol mixtures than it is for other organics. A literature survey shows that wide-ranging data are available on the PV performance of SA and its modified membranes. In this context, the present review addresses the recent advances made in SA membranes for enhanced ethanol dehydration performance during the last decade. Available data since 2010 has been compiled for grafted, crosslinked, blend, mixed matrix, and composite hybrid sodium alginate membranes in terms of separation factor, permeation flux, and pervaporation separation index PSI. The data are assessed with reference to the effect of feed composition, membrane selectivity, flux, and swelling behavior.     

Composite hybrid membrane of chitosan-silica in pervaporation separation of MeOH/DMC mixtures

Chitosan-silica hybrid membranes (CSHMs) were prepared by cross-linking chitosan (CS) with 3-aminopropyl-triethoxysilane (APTEOS). The dynamic behaviors of the CS membrane and the CSHM were investigated in pervaporation (PV) of methanol/dimethyl carbonate (MeOH/DMC) mixtures. The membranes were characterized by X-ray diffraction (XRD), contact angle meter, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The transition state of PV processes were studied. During the PV processes, the amorphous region of the membranes increases and the contact angle between MeOH and the membrane decreases within a range of operating time and then remains almost constant implying a reconstruction occurred on the membrane surface. The silica is well distributed in the CSHM matrix and the thermal stability of the CSHM is enhanced. The time for a PV process to reach a steady state decreases with increasing MeOH concentration or feed temperature, and it is longer for the CSHM than the CS membrane under the same operating condition. Swelling experiments show that the degree of swelling (DS) is greatly depressed by cross-linking CS with APTEOS. Sorption data indicate that the selectivity of solubility and diffusion of the CSHM are greatly improved over the CS membrane. The CSHM presents superior separation behaviors over other membranes with a flux of 1265 g/(hm(2)) and separation factor of 30.1 in PV separation of 70 wt% MeOH in feed at 50 degrees C.     

Two‐Dimensional Membranes: New Paradigms for High‐Performance Separation Membranes

Two‐dimensional (2D) materials with atomic thicknesses have aroused great interest as promising building blocks for the preparation of ultrathin 2D membranes. These 2D membranes can exhibit unprecedentedly high separation permeance owing to their ultrasmall membrane thicknesses and superior selectivity because of their size‐selective nanopores and/or nanochannels. Until now, a large number of 2D membranes with good performance have been reported, highlighting the potential of these novel membranes for efficient liquid and gas separations. Summarized in this review are the latest advances in 2D membranes, with a special focus on industrially attractive separation processes, fabrication methods of laminar membranes, choices of membrane materials, designs of membrane structures, and unique membrane transport properties. Opportunities and challenges of 2D membranes for commercial applications are also briefly discussed.