【作者】 冯文婕；

【导师】 蔡邦肖；

【作者基本信息】 浙江工商大学 ， 食品科学， 2008， 硕士

【摘要】 膜科学技术是一门新兴的高科技,也是一门多学科交叉的科学技术。膜分离过程,已成为食品加工、生物制药、水处理等重要生产中分离与纯化的重要过程,并以得到广泛应用。各种膜分离的过程,又以不同结构和性能的膜为主要决定因素。因此,膜材料和成膜条件,如何控制其结构,以及膜的传递过程等,都是膜科学技术领域的重要内容。近年来,旨在食品加工、生物制药等领域中进行有机物/水混合物的分离,以反渗透（RO）脱盐用的芳香族聚酰胺（PA）类复合膜为支撑膜,采用涂敷法制备聚乙烯醇（PVA）/PA复合膜以及界面缩聚（IP）法制备多层PA复合膜的工艺已有较系统的研究。然而,分离层为单层结构的复合膜在性能方面会受到复合工艺和单一材料的一些限制。因此,将两种不同的成膜方法组合,制备分离层为多层交替结构的具有高性能的复合膜——多层交替复合膜（MLCM）,是成膜技术的一个创新。本文基于PVA膜、PA膜都具有高度水渗透性以及对有机物都有一定的分离能力的特性,在PA类RO复合膜上,通过浸涂PVA形成一薄膜层以及IP工艺得到PA高分子层,强化复合膜的透水性,弥补PA膜的低分离性能,开发PV分离有机物/水混合物的具有特殊分离层结构的新型的MLCM。本方法无需特别的制膜设备和过多的高分子材料,仅需要浸涂和IP两道工艺,就可以获得性能优良的PA复合膜,该工艺设备简单,操作简便安全,制备条件易控。通过现代仪器原子力显微镜（AFM）和扫描电镜（SEM）对MLCM表面结构观测分析,确定通过交替复合工艺将RO用的商品PA膜改性成为具有均匀致密分离层的MLCM,使MLCM在微结构和优先选择渗透性两方面都得到了优化。IP工艺制得的PA层是具有三维空间结构的网状PA聚合物,增加了膜的比表面积,同时具有上紧下松的不对称的致密结构,提高了功能层的有效渗透面积,有利于复合膜选择性和通量的提高;浸涂的PVA交联层起到了三个作用,首先为IP反应提供良好的支撑体,其次为PV分离时优先透过PA皮层的渗透物提供良好的输送通道,再次可将透过项层PA层的渗透物进行又一次的选择性分离,具有双重选择性分离功能。该组合复合工艺解决了其他复合工艺存在的复合膜分离性能取决于单一材料固有性能的问题,有利于复合膜的优先选择渗透性能的提高;PA/PVA的亲水性双层结构,降低了单一分离层的厚度问题,有利于复合膜的渗透通量增加。通过对PA/PVA/PA复合膜制备和传递性能实验的研究表明:（1）采用以下工艺条件制备的MLCM分离性能良好,用于PV分离异丙醇（IPA）/水混合物时,渗透液中水含量(C_P-H2O)大于99wt%。浸涂工艺条件:PVA质量分数为2wt%,交联剂戊二醛为3wt%,热处理条件为150℃,1h;IP工艺条件:水相溶液中间苯二胺（m-PDA）为0.2wt%,浸渍时间为20min,有机相溶液（溶剂为正已烷）中均苯三甲酰氯（TMC）为0.07wt%,浸渍时间为20s,50℃条件下反应5min,缩聚2次。（2） PA/PVA/PA MLCM的渗透通量（J）和分离因子（α）与料液中IPA浓度(C_F-IPA)以及操作温度（T）密切相关。随着C_F-IPA和T值的提高,C_P-H2O始终大于99wt%。通过对实验数据的回归,建立了可预测PA/PVA/PA MLCM通量J值的传质经验关联式:组分水的渗透通量:J_W=0.059(C_F-IPA)²-9.3179C_F-IPA+434.11组分IPA的渗透通量:J_IPA=0.0007(C_F-IPA)²-0.1133(C_F-IPA)+4.5859总通量与T的关联式:J=67171.21exp（-1940.6/T）（3） PA/PVA/PA MLCM可以用多种类型的多孔膜作为支撑膜,其制备工艺具有良好的稳定性和广泛的适用性。（4）经反复实验运行以及长期贮存后的PA/PVA/PA MLCM仍具有良好稳定的PV分离IPA/水混合物的性能。（5） PA/PVA/PA MLCM适于分离各种浓度的IPA/水混合物。通过与精馏耦合的精馏/PV/精馏集成工艺中的模拟实验表明,MLCM的渗透通量达200～270g/m²·h,透过物中水含量大于99.4wt%,具有优良的分离效率。显然,具有特殊多层交替分离层结构的高分离性能的PA/PVA/PA复合膜,可广泛地应用于食品、生物、制药工程中大量溶媒IPA/水混合物的分离纯化。在实际分离工程中将显示出工程应用意义和经济意义。更多还原

【Abstract】 Membrane technology is a new high-tech,and is more than one interdisciplinary science and technology.Membrane separation processes has become an important industrial process in food processing, pharmaceutical industry,chemical industry,water treatment,and other important production.Membrane structure and performances are the main determining factor on all kinds of membrane separation process. Therefore,membrane material and membrane-forming conditions,how to control its structure,as well as membrane transfer process are important parts of membrane science and technology.In recent years,It has been systematic studied that the aromatic polyamide（PA） composite membrane for reverse osmosis（RO） desalination as the support-layer coated with polyvinyl alcohol（PVA） to prepare PVA/PA composite membrane,or prepared multilayer PA composite membrane by interfacial polymerization（IP）,which used for organic/water mixture separation by pervaporation（PV） in food products and pharmaceutical industry,and other areas.However,the performance of those composite membranes is restricted by single composite technology and/or single material.Therefore,it is a technical innovation that the high-performance composite membranes with multilayer separation structure——multilayer composite membrane（MLCM） were prepared by combination of two different composite techniques.Preparation of new polyamide/polyvinyl alcohol/polyamide （PA/PVA/PA） MLCM by the hybrid process of the dip-coating in polyvinyl alcohol solution and the interfacial polymerization（IP） of m-phenyldiamine（m-PDA） and trimesoyl chloride（TMC） with the PA membrane as support for organics mixtures separation was presented in this article.Both PVA and PA are highly hydrophilic,and have ability to separate organics mixtures.The PA composite membrane which performance is excellent can be obtained by dip-coating and IP process. The method is not only without special equipment and too many materials,but also easy to operate and control.In the experiments,the membrane surface structures were observed and analyzed through Atom Force Microscope（AFM） and Scanning Electronic Microscope（SEM）.The results showed that the composition of PA/PVA/PA MLCM on the PA membrane surface was feasible. Moreover,the morphology and the performance of MLCM in separating IPA/water mixtures by PV were satisfying.The PA layer which prepared by IP technique possesses three-dimensional structure,and improved membrane specific surface area.This layer has up-dense and down-loose asymmetric structure in the effective penetration area.The PVA layer played three roles,firstly,as support structure for IP reaction;secondly,as a good transportation access for permeate which priority transported through the layer by PV; thirdly,as further permselective separation layer for permeate.The combination composite methods solved the problems about the composite membrane performance depends on a single material and/or single method,and improved membrane permeability.PVA/PA double-layer hydrophilic structure solved the thickness problem of a single layer,and was conducive to increase the flux.The effects of the membrane-forming conditions and the operation conditions on the separation performances of PA/PVA/PA MLCM were emphatically investigated.The following conclusions can be drawn from the experimental results.（1） The performance of MLCM which was prepared by the following conditions is satisfying.The concentration of water in the permeation(C_p-H2O) of MLCM was more than 99wt%for separate IPA/water mixtures by PV. The preferred dip-coating process conditions are:the concentration of PVA was 2wt%,the concentration of crosslinking agent——GA was 3wt%,the temperature and time of heat treatment were 150℃and 1h, respectively.The preferred IP process conditions were:the concentrations of m-PDA and TMC were 0.2wt%and 0.07wt%respectively,the soaks time of the support in aqueous phase and organic phase was 20min and 20s respectively,the temperature and time of heat reaction were 50℃and 5min respectively,then IP 2 times.（2） The flux（J） and separation factor（α） of PA/PVA/PA MLCM were closely related to the concentration of IPA in the feed(C_F-IPA) and the operation temperature（T）.With the increasing of C_F-IPA and T,C_P-H2O was always more than 99wt%.Through the regression of experimental results,the forecast equations of the flux of water and isopropanol transported through the PA/PVA/PA MLCM were established.For flux of water:J_w = 0.059(C_F-IPA)²-9.3179C_F-IPA+434.11For flux of IPA:J_IPA = 0.0007(C_F-IPA)²-0.1133(C_F-IPA)+4.5859For total flux:J= 67171.21exp（-1940.6/T）（3） The composite technique has preferable stability and extensive applicability,and many kinds of porous membrane could be used as support to prepare PA/PVA/PA MLCM.（4） PV performance of PA/PVA/PA MLCM was stable for separating IPA/water mixtures.（5） PA/PVA/PA MLCM was suitable for separation of IPA/water mixture with various concentrations by PV.Simulation experiments in integration process of distillation and PV showed that:the flux of MLCM reached 200～270g/m².h and C_P-H2O was always more than 99.4wt%, could possess excellent separation efficiency and economic benefits. Apparently,PA/PVA/PA MLCM could be applied to the separation of IPA/water mixtures in food,biological and pharmaceutical engineering.PA/PVA/PA MLCM with high separation performance revealed its important application values in the actual separation projects.更多还原