荷电聚砜超滤膜层层自组装改性制备纳滤膜及其脱盐性能研究

发布时间：2018-02-13 04:36

  本文关键词： 层层自组装 聚电解质多层膜 复合纳滤膜 盐截留　出处：《武汉工程大学》2015年硕士论文　论文类型：学位论文

【摘要】：当今社会,随着人口数量的增长及社会经济的发展,优质水资源少、水体污染严重的问题逐渐凸显出来。水处理技术作为解决水资源短缺问题的手段之一受到人们的广泛关注。膜分离作为水处理手段之一除了具有能耗低、分离效果好、工作条件温和、工艺简单等优点外,还能浓缩回收废水苦咸水中的有用物质,达到资源全利用的目的。目前用于水处理中的膜分离技术主要有微滤、超滤、纳滤、反渗透,其中纳滤主要用于饮用水的软化以及工业用水的除盐等。为了解决目前市场上商业纳滤膜的通量低选择性差的缺点,我们以聚砜超滤膜为基膜,在其上组装聚电解质多层膜制备了高通量高选择性的复合纳滤膜。聚电解质层层自组装制备多层膜具有方法简单、膜组成和结构易于控制、可制备具有特殊功能的功能性复合膜等优点,这一技术已经成为制备多层超薄膜的重要方法之一。由于聚电解质层层自组装膜具有表面电荷强度高、厚度薄的特点,非常适合将其应用于兼具高通量和高选择性的复合纳滤膜超薄分离层。本文以聚乙烯亚胺(PEI)为聚阳离子电解质,聚丙烯酸(PAA)、聚苯乙烯磺酸钠(PSS)为聚阴离子电解质,利用聚电解质自组装技术对Alfa Laval UFX-10聚砜超滤膜进行表面改性,制备了自组装复合纳滤膜并将其用于盐类分离和浓缩的研究。实验研究了聚电解质双层数、自组装时间、聚电解质溶液pH值、聚电解质浓度、最外层电解质、支撑电解质种类、支撑电解质浓度等工艺参数对聚电解质改性复合纳滤膜水通量以及盐截留率的影响,并考察了膜的稳定性。实验结果表明,聚电解质双层数、自组装时间、聚电解质溶液pH、最外层聚电解质层种类等条件对改性膜性能影响较大,支撑电解质种类、聚电解质浓度对多层膜的性能影响较小。随着聚电解质多层膜双层数的增加,复合膜的截留性能提高,同时水通量降低。最外层聚电解质层种类对膜的盐截留性能影响较大,对水通量影响较小。通过衰减全反射红外光谱对多层膜进行分析。PEI/PSS多层膜ATR-IR谱图与基膜基本重合,随着双层数的增加,1015cm-1处磺酸基的特征吸收峰峰强度略微增加,表明PSS层数增加。PEI/PAA多层膜ATR-IR谱图我们可以明显看出1738cm-1处的羧基吸收峰峰强度增大。通过ATR-IR表征表明PSF基膜上发生了聚电解质层层自组装过程。通过SEM对多层膜表面形貌进行了表征,发现经过聚电解质层层自组装改性后,膜的表面形貌发生了变化,多层膜表面变得更加光滑平整。对改性纳滤膜表面接触角的表征结果表明,基膜经过聚电解质自组装改性以后膜表面的亲水性显著增强。通过研究各种工艺参数对膜性能的影响,获得最佳的制膜工艺条件为:支撑电解质NaCl浓度0.5 mol/L、聚电解质浓度0.02 mol/L、聚电解质溶液pH为7左右、聚电解质组装时间15分钟。在此条件下制备的(PEI/PSS)5、(PEI/PSS)_(5.5)、(PEI/PAA)5、(PEI/PAA)_(5.5)的截留率分别为71.15%、79.5%、60.19%、42.13%,此时膜的通量分别为22.86L/(m2·h)、17.14 L/(m2·h)、4.29 L/(m2·h)、23.57 L/(m2·h)。所制得的膜稳定性较好,在4bar压力下连续运行6小时、累积运行18小时内膜通量与盐截留率变化较小。从多方面研究了聚电解质改性膜的性能特征。实验结果表明,不同类型多层膜的盐截留性能差别很大,同种多层膜对不同盐溶液的截留率也不相同,具有一定的选择性。考察了多层膜截留性能与不同操作条件之间的关系,研究了料液温度、pH、压力、浓度等操作因素对膜截留性能的影响,并进行了简单的盐类分离实验,总结了聚电解质改性纳滤膜的性能特点。
[Abstract]:In today's society, with the development of the growth of population and social economy, high-quality water resources, serious water pollution problem is more prominent. Water treatment technology as one of the means to solve the shortage of water resources have attracted extensive attention. As a means of water treatment in addition to membrane separation has the advantages of low energy consumption, good separation effect, work under mild conditions, simple process and other advantages, but also useful material in wastewater concentration and recovery of brackish water, to achieve full utilization of resources. Currently used for membrane separation technology in water treatment include microfiltration, ultrafiltration, nanofiltration, reverse osmosis nanofiltration, which is mainly used for drinking water and industrial water softening desalting to. To solve the current commercial nanofiltration membrane flux on the market low selectivity, we using polysulfone ultrafiltration membrane as support membrane, assembly of polyelectrolyte multilayer films were prepared in the high throughput Composite nanofiltration membrane selectivity. Polyelectrolyte self-assembled multilayer film has the advantages of simple method, film composition and structure is easy to control, can be prepared with special functional composite film and other advantages, this technology has become one of the important methods for preparing multilayer ultrathin films. The polyelectrolyte self-assembled film has the surface charge characteristics of high strength, thin thickness, very suitable for its application in both high throughput and high selectivity of the composite membrane. The ultrathin separating layer with polyethyleneimine (PEI) as polycation electrolyte, polyacrylic acid (PAA), sodium polystyrene sulfonate (PSS) as polyanion electrolyte, using self-assembled polyelectrolyte technology of Alfa Laval UFX-10 polysulfone ultrafiltration membrane surface modification, preparation of self assembled composite nanofiltration membrane was used in the study of separation and concentration of salts. Experimental study of polyelectrolyte Self-assembled Bilayer number. With time, the polyelectrolyte solution pH, concentration of polyelectrolyte, the outermost layer of supporting electrolyte, electrolyte species, supporting electrolyte concentration and other parameters on the effect of polyelectrolyte modified composite nanofiltration membrane water flux and salt rejection rate, and the effect of membrane stability. The experimental results show that the number of polyelectrolyte bilayers, self-assembly time. Polyelectrolyte solution pH, the outermost layer of the polyelectrolyte layers and other types of conditions have a greater impact on the modified membrane performance, supporting electrolytes, polyelectrolytes concentration affects the performance of multilayer small. With the increase of the number of bilayers of polyelectrolyte multilayers, improve the rejection performance of the composite membrane, and the water flux decreased. The outermost layer of polyelectrolyte type the membrane salt rejection performance influence on small water flux affected by attenuated total reflection infrared spectroscopy analysis of multilayer.PEI/PSS multilayer ATR-IR spectra and membrane basic weight He, along with the increase of the number of bilayers, characteristics of 1015cm-1 sulfonic acid absorption peak strength increased slightly, showed that PSS increased layers of.PEI/PAA multilayer ATR-IR spectrum we can clearly see that 1738cm-1 at the carboxyl absorption peak intensity increases. The results indicated that PSF membrane had polyelectrolyte layer by layer self-assembly process characterized by ATR-IR through SEM. The surface morphology of the multilayer films were characterized by polyelectrolyte layer by layer self-assembly modification, changes in surface morphology of the film, multilayer film surface becomes more smooth. Show that the modified nano characterization of membrane surface contact angle of the membrane by self assembled polyelectrolyte modified after the hydrophilicity of the membrane surface significantly enhanced. By studying the effect of different process parameters on membrane performance, obtained the optimum process conditions for membrane supporting electrolyte NaCl concentration of 0.5 mol/L, the polyelectrolyte concentration 0.02 mol/L, poly 鐢佃В璐ㄦ憾娑瞤H涓，

本文编号：1507331