【作者】 帅师；

【导师】 俞三传；

【作者基本信息】 浙江理工大学 ， 化学工程（专业学位）， 2013， 硕士

【摘要】 纳滤是近20年来发展起来的一种新兴膜分离技术，纳滤膜对多价离子以及分子量大于200Da的有机物有较高的截留率，所以纳滤广泛地应用于有机物的脱盐与浓缩、不同分子量有机物的分级、水质软化、废水脱色等领域。纳滤膜对不同物质的分离特性、分离机理、分离过程模拟等一直是当前纳滤膜分离技术领域的研究热点。为了更准确的预测纳滤膜的分离性能和指导实际生产应用，本论文开展了基于纳滤膜技术的水体中有机物的分离特性研究。论文首先选择了两种具有不同特性的纳滤膜NF1#和NF2#，在系统评价纳滤膜Zeta电位、接触角、截留分子量、无机盐分离性能等基本膜性能参数的基础上，采用错流分离试验，研究纳滤膜对不同有机物环己酮、苯乙醇、葡萄糖、蔗糖、苯甲酸、水杨酸和邻苯二甲酸等的分离性能，探讨了溶质性质、溶液pH、操作压力、操作温度、料液浓度、回收率及高浓度盐等因素对纳滤去除有机物性能的影响。然后，分别采用细孔和电荷浓差极化模型，结合纳滤膜的MWCO与中性有机物的分子量Mn以及纳滤膜表面的Zeta电位和带电有机物的物化性质，分别对纳滤膜分离中性有机物和荷电有机物的实验数据进行拟合分析，探究影响纳滤膜去除水体中有机物性能的主要影响因素。最后，基于拟合的电荷浓差极化模型的基础上，将纳滤膜应用于实际的甘氨酸生产工艺中，进行了相关的纳滤分离与浓缩实验。得到以下结论：（1）纳滤膜表征表明：不同的纳滤膜，由于制备工艺与材料不同，膜性能差异较大。Zeta电位测试表明试验所用的两种纳滤膜表面均为为两性表面，NF1#纳滤膜等电点在pH=3.8，NF2#纳滤膜在pH=4.04。在pH>4.04时，两种纳滤表面均呈负电性，而且随着pH增大，负电越强。NF1#膜的切割分子量（MWCO）为310Da，NF2#膜的MWCO为185Da。两种纳滤膜对不同有机物的分离性能差异明显。（2）有机物分离试验研究表明：纳滤膜脱除水中有机物主要受膜切割分子量和表面电荷影响。溶液pH对纳滤膜截留中性有机物的影响不明显，其截留主要与膜MWCO相关；纳滤膜对带电有机物的截留率与膜表面带电基团与带电物质之间的静电作用力有关，与溶液pH密切相关，静电排斥机理较筛分机理占主导地位。（3）对于中性有机物，通过假定纳滤膜的MWCO所对应的有机分子Stokes半径与膜的有效细孔半径相等，通过测定纳滤膜MWCO及对应的膜细孔半径rp，结合溶质半径rs与Mn之间关系，利用细孔模型能准确地预测纳滤膜对中性物质的截留率与渗透通量的关系。（4）对于带电有机物，通过实验测出纳滤膜在等电点时对带电物质的截留数据即Runcharged，然后运用电荷浓差极化模型，就能准确地预测纳滤膜在不同pH下对带电物质的截留。（5）将纳滤膜技术应用于甘氨酸生产工艺中，通过电荷浓差极化模型预测，NF2#纳滤膜在pH=7时，对甘氨酸的截留率为88%，而实际测得NF2#膜对甘氨酸的截留率为83.3%，与预测值存在一定的偏差，其误差主要是由于废水中无机盐和其他小分子物质的影响造成的。更多还原

【Abstract】 Nanofiltration (NF), as a newly developed membrane separation process, has played animportant role in the field of membrane filtration technology in recent20years. The NFmembrane usually exhibits relatively high rejections to multivalent ions and organic compoundswith molecular weight larger than200Da and low rejection to monovalent ions. Therefore,nanofiltration membrane has been widely used in the desalination and concentration of organics,separation of organic compounds with different molecular weights, water softening and reducingthe clour of wastewater and so on. The mass transfer, separation mechanism, mathematicalmodel of nanofiltration process are the major research interests in the field of nanofiltration.In order to predict the separation performance more accurately and to guide the applicationof nanofiltration membrane, this paper focused on the study of the removal of organiccompounds from aqueous solution through nanofiltration. Two commercial nanofiltrationmembranes of different characteristics, NF1#and NF2#, were adopted. After measurements ofmembrane properties in terms of zeta potential, contact angle, MWCO, inorganic salt rejectionand water flux, the membranes were employed to conduct cross-flow permeation tests fordetermination the the separation performance to different organics including cyclohexanone,benzene ethanol, glucose, sucrose, benzoic acid, salicylic acid and phthalic acid. The influencesof solute property, solution pH, operating pressure, operating temperature, feed concentration,recovery rate and concentration of the co-solute salt on the removal efficiency of thenanofiltration membranes to organic compounds were investigated. The pore model and thecharge concentration polarisation model were adopted to simulate the experimental data of theremoval efficiency of the membranes to neutral and charged organic compounds, respectively,by using the MWCO of nanofiltration membrane and the molecular weigh (Mn) of neutralorganic compounds, and the Zeta potential of membrane surface and the physicochemicalproperties of charged organic compounds, respectively. Finally, nanofiltration membrane wasused to separate and concentrate glycine under netural pH. The removal efficiency was predictedthrough the charge concentration polarisation mode and compared with the experimetanl data.The conclusions are as follows:（1）The characterization of membrane showed that the two nanofiltration membranes usedin this study had different performances due to the difference of manufacture technology and material. The measurement of zeta potential showed that the two membranes had amphotericsurfaces. The isoelectric points of membranes NF1#and NF2#were pH=3.8and pH=4.04,respectively. When the pH was higher than4.04, these two nanofiltration membranes werenegatively charged, and the charge was stronger with the increase of pH. The MWCOs of NF1#and NF2#membranes were310Da and185Da, respectively. The two nanofiltration membranesshowed different separation performances to organic compounds.（2）The results of separation experiments with aqueous solution containing differentorganic compounds showed that the removal of organic compounds from aqueous solutionthrough nanofiltration was mainly controlled by the MWCO and the surface charge of themembrane. The rejction of the nanofiltration to neutral organic compounds was mainlydetermined by the MWCO of membrane used, and was less affected by the solution pH. For thecharged organic matter, the rejection was mainly determined by the electrostatic interactionbetween charged functional groups on the surface of the membrane and the charged material, andwas largely affected by the solution pH.（3）For the neutral organic compounds, the separation was simulated using pore modelbased on the assumption that the effective pore radius of the membrane is equal to the organicmolecule Stokes radius corresponding to the MWCO measured. The rejection to neutral organiccompound under certain permeation flux could be accurately predicted using the relationshipbetween the membrane pore radiu rpand the MWCO and the correlation between solute radius rsand Mn.（4）For the charged organics, the rejections of the nanofiltration membrane under differentpHs could be accurately predicted through the charge concentration polarisation model bymeasuring the Runcharged.(5) The application of nanofiltration membrane in separation and concentration glycineaqueous solution demonstrated that, under netural pH, the predicted rejection of membrane NF2#to glycine through the charge concentration polarisation model was88%, while the actualrejection was83.3%. The deviation between the predicted and actural values was mainly due tothe influence of inorganic salts and other small molecules presented in the waste water.更多还原