【作者】 周翀；

【导师】 王湛；

【作者基本信息】 北京工业大学 ， 应用化学， 2007， 硕士

【摘要】 抗污染膜的制备是解决膜污染问题的根本途径,是实现膜技术在其应用领域中长期、稳定运行的关键。本实验所进行的PVDF/PMMA/CA共混超滤膜的制备研究是在原有传统的相转化法的基础上引入化学反应,通过制膜液中的冰乙酸和凝胶浴中的碳酸钠反应生成二氧化碳气体的方法来达到调节膜孔径的均匀分布和提高膜的抗污染性能的目的。本文首先采用L32(49)正交试验表,通过研究各因素对PVDF/CA共混微滤膜性能的影响程度,验证多元线性回归模型的可行性。其次以纯水通量、料液通量、截留率作为考察指标确定了影响PVDF/PMMA/CA共混超滤膜性能的主要因素,具体分为以下几步:(1)采用L18(2×37)正交试验表,通过极差分析法以及多元线性回归模型的分析,定量判断了各因素对膜性能的影响程度;(2)采用L27(310)正交试验表,考虑添加剂种类和添加剂含量的交互作用以及溶剂种类和添加剂种类的交互作用,通过正交试验完成实验数据的采集,并对其进行多元线性回归分析;(3)比较不同凝胶浴种类下制得膜的孔径分布和环境扫描电子显微镜照片;(4)使用研究级万能显微镜,分别观测最佳制膜液组成在不同凝胶浴种类下的成膜过程。实验结果表明:(1)正交试验与多元线性回归模型相结合可以有效地优化制膜条件。(2)固含量、溶剂种类、添加剂种类、添加剂含量、凝胶浴种类是PVDF/PMMA/CA共混超滤膜性能的主要影响因子,其中固含量、添加剂种类是显著影响因子。以X1(固含量)、X2(溶剂种类)、X3(添加剂种类)、X4(添加剂含量)、X7(溶剂种类和添加剂种类的交互作用)五个影响因子为参变量,Y4(综合考虑纯水通量、料液通量和截留率三个指标)为因变量进行多元线性回归运算,得到回归方程:Y 4 = 4. 9211?1.8714X1?0.4618X2+0.7187X3?0.1527X4?0.2922X7。(3)最佳的超滤制膜液配方以及凝胶条件:固含量为16%、溶剂为DMF、添加剂PEG2000含量为2%、冰乙酸含量为10%、凝胶浴为碳酸钠水溶液、凝胶时间30分钟。在此优化条件下制备出孔径分布为0.07~0.10μm的PVDF/PMMA/CA共混超滤膜,其在0.1MPa室温条件下的纯水通量为197.26~265.24mL·cm-2·h-1,BSA料液通量为14.87~15.96mL·cm-2·h-1,对BSA的截留率为89.73~93.91%。(4)凝胶速度随时间的增长而下降。化学反应对凝胶速度影响较大,能显著增加膜的凝胶速度。更多还原

【Abstract】 The preparation of high quality antifouling membrane is one of the most efficient methods to improvement antifouling characteristics of the membrane. PVDF/PMMA/CA blend UF membrane was prepared by chemical reaction way is based on the traditional phase-inversion method. The antifouling characteristics of the membrane is enhanced due to the uniformity of the membrane pore size, which is modulated by the carbon dioxide (CO2) gas, produced by a chemical reaction between glacial acetic acid (CH3COOH) in the casting solution and sodium carbonate (Na2CO3) as category of coagulation medium.At first, an orthogonal table with nine factors and four levels L32 (49) was designed to confirm the feasibility of linear multi-regression model by study the influence degree of factors on characteristics of PVDF/CA blend microfiltration membrane. Secondly, the pure water flux, the feed solution flux of BSA and the observed retention of BSA had been used to estimate the characteristics of the PVDF/PMMA/CA blend UF membrane, the steps is as follows: (1) An orthogonal table with eight factors and three levels L18 (2×37) was designed and the influence degree of factors on characteristics of membrane had been determined by range analysis method and linear multi-regression model. (2) On this basis, the orthogonal table L27 (310) was designed to study both the interaction between additive content and additive species, additive species and solvent species. The linear multi-regression model was analyzed with the data collected by the orthogonal test. (3) The pore size distribution and SEM images of the membranes was compared, respectively. (4) By using optical microscope observed the process of membrane formation under optimum condition for preparing the PVDF/PMMA/CA blend UF membrane.The results showed that: (1) The combination of orthogonal table and linear multi-regression model is an efficient method to ascertain the optimum preparation conditions for the porous membrane-making process; (2) Solid content, solvent species, additive species, additive content, category of coagulation medium are influencing factors on the characteristics of the PVDF/PMMA/CA blend UF membrane, and among which solid content and additive species are remarkable influencing factors; The relationship is as follows: , where, Y4 is a function that simultaneity consider the influence of the pure water flux, feed solution flux and observed retention, X1 is solid content, X2 is solvent species, X3 is additive species, X4 is additive content, X7 is the interaction between additive content and additive species; (3) When solid content of PVDF/PMMA/CA is 16%, using DMF as solvent, PEG2000 with 2% as additive, content of glacial acetic acid (CH3COOH) is 10%, category of coagulation medium is aqueous solution of sodium carbonate (Na2CO3), gelation time is 30 minutes; (4) The gelation rate decreased as the gelation time increasing. Chemical reaction affect gelation rate intensively, can increase gelation rate obviously.Under this optimization condition of the membrane preparation, the PVDF/PMMA/CA blend UF membranes with uniform membrane pore size distribution and high pure water flux could be prepared, which pore size distribution is 0.07 ~ 0.10μm; the pure water flux is 197.26 ~ 265.24 mL·cm-2·h-1; the protein flux is 14.87 ~ 15.96 mL·cm-2·h-1 and the observed retention is 89.73 ~ 93.91%. The three parameters above are all measured under the 0.1MPa pressure at room temperature.更多还原