液体溶解—凝聚法调控聚合物滤膜结构及其水处理性能研究

发布时间：2018-03-20 08:11

本文选题：聚合物滤膜　切入点：结构调控　出处：《哈尔滨工业大学》2014年硕士论文　论文类型：学位论文

【摘要】：膜法水处理技术以其适用范围广、分离效率高、无二次污染等特点，在水环境污染日益严重，水质安全需求越来越高的形势下，发挥了其独特的优势，受到了全世界的关注。膜的透水性和分离性能都会受到膜结构的显著影响，均匀的膜孔会增加水通量，实现不同粒径物质的分级截留。传统的浸没沉淀无法制备均孔膜；而其他如径迹刻蚀法、嵌段共聚物自组装等可实现膜孔径均匀的方法，由于技术特殊、成本较高，并不适合水处理行业大规模的应用，因此，开发一种简便、通用、可调控的均孔膜制备方法在水处理应用领域具有重大意义。选择挥发性强的二氯甲烷、二氧六环或丙酮作为溶剂，在溶剂中具有一定溶解度的丙二醇、二甘醇、丙三醇等非挥发性液体为添加剂，通过改变铸膜液组成，在聚砜、聚苯乙烯、聚偏氟乙烯膜表面得到了均匀蜂窝状结构，，而对于醋酸纤维素膜，则可以得到蜂窝状膜孔和纳米级膜孔这两种结构，蜂窝状孔径为1~3μm，而纳米级膜孔可在5~50nm范围内调控。这两种结构的形成均可由所提出的液体添加剂溶解-凝聚原理解释——溶剂的快速挥发使界面处聚合物和添加剂浓度增加，添加剂由初始铸膜液中分散的小分子凝聚为聚合物的稀相核，在溶剂挥发完全，聚合物固化后，稀相核处则留下了排列规整、尺寸均一的孔结构。为实现溶剂的快速挥发，旋涂法和真空法被选择为制膜方法。蜂窝状结构可较大幅度的提高材料表面的疏水性能，具有蜂窝状结构的聚砜、聚苯乙烯、聚偏氟乙烯的接触角分别增加了32°，28°和13°。纳米级膜孔尺寸可通过改变聚合物浓度调控，对不同粒径的颗粒实现较精密的分离，醋酸纤维素质量分数为5%、7%、9%的纳米级均孔醋酸纤维素膜分别对粒径大于20nm、13.5nm、5nm的金颗粒有较高的去除率。均孔膜较为致密，水通量相对较小，但两类均孔膜对牛血清蛋白有一定的截留效果，最高可达到97.6%和84.8%。纳米级均孔醋酸纤维素膜相对未改性的致密膜具有一定的抗污染能力。与传统浸没沉淀法制得的较致密聚砜膜相比，均孔膜对松花江原水中胶体、悬浮物和有机物有很好的净化效果，浊度、TOC和UV254最低可达0.15NTU、1.59mg/L和0.011cm-1。两类均孔膜对原水中Fe、Mn、Al的去除率几乎可达100%，对普通超滤膜无法截留的Ca和Mg也有一定的截留效果。
[Abstract]:Because of its wide application range, high separation efficiency and no secondary pollution, membrane water treatment technology has brought into play its unique advantages in the situation of increasingly serious pollution of water environment and higher demand for water quality safety. The water permeability and separation performance of the membrane will be significantly affected by the membrane structure. The uniform membrane pore will increase the water flux and achieve the separation of different particle size. The traditional immersion precipitation can not be used to prepare the homopolypore membrane. Other methods, such as track etching, block copolymer self-assembly and so on, can realize the uniform pore size of membrane. Because of the special technology and high cost, it is not suitable for the large-scale application of water treatment industry. It is of great significance in the field of water treatment to control the preparation of homopolymer membrane. The volatile non-volatile liquids, such as dichloromethane, dioxane or acetone, which have a certain solubility in the solvent, are selected as additives. By changing the composition of the casting solution, the polysulfone, diethylene glycol, glycerol and other non-volatile liquids are used as additives. On the surface of polystyrene, polyvinylidene fluoride (PVDF) membrane, homogenous honeycomb structure was obtained, while for cellulose acetate membrane, honeycomb membrane pore and nanometer membrane pore were obtained. The honeycomb pore size is 1 ~ 3 渭 m, while the nanometer membrane pore can be controlled in the range of 550 nm. The formation of these two structures can be explained by the proposed principle of solubilization and condensation of liquid additives, and the rapid volatilization of -solvent can increase the concentration of polymer and additive at the interface. The additives are condensed from dispersed small molecules in the initial casting film liquid to the dilute phase nucleus of the polymer. After the solvent volatilizes completely and the polymer is cured, the pore structure of the dilute phase core is arranged and uniform. In order to realize the rapid volatilization of the solvent, Spin-coating method and vacuum method were selected as film preparation methods. Honeycomb structure can greatly improve the hydrophobicity of the surface of the material. The contact angle of polysulfone, polystyrene and polyvinylidene fluoride with honeycomb structure increases by 32 掳~ 28 掳and 13 掳respectively. The pore size of nano-scale membrane can be controlled by changing the concentration of polymer. For the particle with different particle size, the cellulose acetate film with 5% cellulose acetate mass fraction has a higher removal efficiency for gold particles with diameter larger than 20 nm and 13.5nm ~ (-1) nm, respectively, and the cellulose acetate membrane with average pore size of 9% has a higher removal rate for gold particles with particle size larger than 20 nm and 13.5nmN ~ (-1) nm, respectively. The homopolymer membrane was compact and the water flux was relatively small. However, the two kinds of homo-pore membranes had a certain retention effect on bovine serum protein (BSA). The highest values are 97.6% and 84.8.The nanosized homoporous cellulose acetate membrane has a certain antifouling ability compared with the unmodified dense membrane. Compared with the dense polysulfone membrane prepared by the traditional immersion precipitation method, the homoporous membrane has a good effect on the colloid in the raw water of Songhua River. Suspended solids and organic matter have a good purification effect, the turbidity of TOC and UV254 can be as low as 0.15 NTU 1.59 mg / L and 0.011 cm-1.The removal efficiency of the two kinds of homopolypore membranes can almost reach 100%, and the removal rate of Ca and mg which can not be intercepted by the ordinary ultrafiltration membrane has a certain effect.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU991.2

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