含单宁酸仿生分离层制备复合纳滤膜的研究

发布时间：2018-04-26 15:43

本文选题：纳滤膜 + 仿生粘合　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：水资源短缺已经成为当今社会面临的严峻问题,而染料废水的排放也一直威胁着全球性的水安全。传统的用于处理染料废液的方法包括絮凝、吸收和化学降解等,但是这些过程中往往会带来二次污染问题。相比而言,发展于二十世纪六十年代的膜分离技术节能、高效、环保、操作简单。纳滤膜作为一种压力驱动型分离膜,截留分子量在200~1000 Da范围内,可以在废水处理、开发水的再利用方面发挥重要作用。用简单的工艺制备出性能优异的纳滤膜是科学家面临的一大挑战。单宁酸(TA)作为一种天然的植物多酚,具备良好的生物粘附性和丰富的物理化学性能。本文首先利用TA与金属离子的螯合作用,以TA作为有机配体,分别选用过渡金属离子Ag+、Co~(2+)、Ni~(2+)、Cu~(2+)、Fe3+作为无机交联剂,在超滤膜表面形成稳定的交联网络结构。经过初步筛选发现,当固定二者的比例为1:1时,所得到的TA/Co~(2+)、TA/Ni~(2+)复合纳滤膜的渗透通量分别为42.5 L m~(-2) h~(-1) bar~(-1)和45.6 L m~(-2) h~(-1)bar~(-1),要比其他的高出3~4倍。为了进一步研究金属离子浓度对所形成涂层结构的影响,制备了不同比例下的TA/Ni~(2+)涂覆复合纳滤膜。改变TA与金属离子Ni~(2+)的配比从2:1、1:1、1:2至1:3,水通量呈现出先增加后降低的趋势。当调节TA与Ni~(2+)的比例为1:2时,水通量达到最高为56.1 L m~(-2) h~(-1) bar~(-1),此时纳滤膜对有机染料孟加拉玫瑰红的截留率是95.3%。结合TA分子结构中含有的大量酚羟基基团,在水溶液中与聚乙烯亚胺(PEI)之间存在强烈的氢键作用和静电作用,通过一步组装在基底表面形成涂层结构。这部分实验主要考察了TA和PEI的浓度,以及组装层数对于纳滤膜分离性能的影响。研究发现,该法制备的复合纳滤膜的表面带有部分正电荷,对正电性染料的截留更加有效。当PEI的浓度固定时,随着TA浓度的增加,在膜的表面形成的选择层结构更加致密,渗透通量随着TA浓度的增加而降低,对有机染料甲基蓝的截留率从85.5%到99.8%,而对维多利亚蓝B的截留率则是从88.2%提高到了100%。与以TA浓度作为变量不同的是,改变外层PEI的浓度,更多地影响到的是膜表面的亲水性,水接触角从53.1o下降到18.6o,水的渗透通量增加。另外,通过反复组装还可以对该纳滤膜的性能实现进一步调节。
[Abstract]:The shortage of water resources has become a serious problem in our society, and the discharge of dye wastewater has been threatening the global water security. The traditional methods used to treat dye waste liquid include flocculation, absorption and chemical degradation, but these processes often bring secondary pollution problems. In contrast, the membrane separation technology developed in the 1960's is energy efficient, environmentally friendly and easy to operate. Nanofiltration membrane, as a kind of pressure driven separation membrane, with a molecular weight of 200 ~ 1000Da, can play an important role in wastewater treatment and water reuse. The preparation of nanofiltration membranes with excellent performance by simple process is a great challenge for scientists. As a kind of natural plant polyphenols, TAA has good bioadhesion and abundant physical and chemical properties. In this paper, a stable cross-linking network structure was formed on the surface of ultrafiltration membrane by the chelation of TA with metal ions, using TA as organic ligand, and the transition metal ion Ag / CoCoC _ (2) O _ (2) Ni ~ (2) C _ (2) O _ (2) C _ (2) O _ (2) Fe _ (3) as inorganic crosslinking agent. After preliminary screening, it was found that the permeable fluxes of the composite nanofiltration membranes were 42.5 L ~ (m ~ (-1) and 45.6 L ~ (-1) ~ (-1) bar-1 ~ (-1) bar-1m ~ (-1), respectively, when the fixed ratio of them was 1:1, which was 3 ~ 4 times higher than that of the other membranes, and the results showed that the permeation flux of the composite nanofiltration membranes was 42.5 L ~ (-1) and 45.6 L ~ (-1) ~ (-1) bar-1 ~ (-1) ~ (-1), which was 3 ~ 4 times higher than that of the others. In order to further study the effect of metal ion concentration on the structure of the coating, the composite nanofiltration membrane (TA/Ni~(2) coated with different ratio was prepared. When the ratio of TA to Ni~(2) was changed from 2: 1 to 1: 1: 2 to 1: 3, the water flux increased first and then decreased. When the ratio of TA to Ni~(2 was adjusted to 1:2, the water flux reached the maximum of 56.1 L / m ~ (-2) 路h ~ (-1) ~ (-1) ~ (-1) ~ (-1) ~ (-1) ~ (-1), and the rejection rate of the nanofiltration membrane to the organic dye, Bengal rose red, was 95.3%. In combination with a large number of phenolic hydroxyl groups in TA molecular structure, there is a strong hydrogen bond and electrostatic interaction between the hydroxyl group in aqueous solution and polyethylene imide (PEI). The coating structure is formed on the substrate surface by one-step assembly. The effects of TA and PEI concentrations and the number of assembly layers on the separation performance of nanofiltration membranes were investigated. It is found that the surface of the composite nanofiltration membrane prepared by this method has partial positive charge, which is more effective for the retention of positive dyes. When the concentration of PEI was fixed, with the increase of TA concentration, the selective layer formed on the surface of the membrane became denser, and the permeation flux decreased with the increase of TA concentration. The rejection rate of organic dye methyl blue increased from 85.5% to 99.8%, while that of Victoria blue B increased from 88.2% to 100%. Different from TA concentration, the hydrophilicity of membrane surface is more affected by changing the concentration of outer PEI, the water contact angle decreases from 53.1 o to 18.6 o. the permeation flux of water increases. In addition, the performance of the nanofiltration membrane can be further adjusted by repeated assembly.
【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】：2017
【分类号】：TQ051.893

【参考文献】