金属有机骨架复合膜的制备及其抗污染机制研究

发布时间：2018-02-04 05:30

本文关键词： 膜有机污染海水淡化金属有机骨架材料抗污染性能　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：膜分离技术作为一种新型的现代分离技术,既能对废水中存在的杂质及污染物进行有效的截留以及去除,又能对水中的可利用物质进行回收再利用,还具有节能、无二次污染、设备简单易操作,效率高等优点,因此在水处理技术中得到了广泛应用及推广。但在膜分离技术中不可避免的存在膜污染问题,膜污染现象通常表现为膜渗透通量下降,分离效率降低等。会导致能耗加大、膜使用寿命大大缩减,进而增加处理成本。因此制备具有较优良抗污染性能的膜材料在废水处理,海水淡化等领域具有重大意义。本论文针对在膜分离技术过程中的膜有机污染以及海水淡化效率较低等问题,以金属有机骨架ZIF-8为载入材料,通过层层自主装技术(LBL)制备具有较高渗透通量以及较好抗污染性能的金属有机骨架复合膜材料,在正渗透系统中评估所制备的复合膜材料在海水淡化方面的性能,在终端过滤系统中考察制备的复合膜材料对天然有机污染物(NOM)的抗污染性能并利用XDLVO理论解析其抗污染机理。论文的主要研究内容与结果如下:(1)采用层层自组装技术,在正渗透膜表面负载金属有机骨架材料ZIF-8,制备金属有机骨架正渗透膜。并利用扫描电子显微镜(SEM)、原子力显微镜(AFM)以及X射线能谱仪(XPS)等表征手段证明膜材料已成功制备,ZIF-8已在正渗透膜表面形成连续的共生性较好的膜层,且膜表面变得较为粗糙。接触角测试表明金属有机骨架正渗透膜具有较小的接触角,相对于FO膜展示出了较好的亲水性能,从而阻止污染物在膜材料表面的沉积,附着以及黏附。并在正渗透装置中,测试金属有机骨架正渗透膜对不同价态盐离子去除的普适性,分别选取KC1、NaCl、MgCl2与CaCl2作为驱动液,去离子水作为原水。当负载了 0.5%(w/v)的ZIF-8时,膜材料的水通量从20LMH提高至31LMH,提高幅度高达55%。而且其相比于FO膜展示出了较低的反向盐通量,对不同价态的盐离子都具有较好的截留效果。说明ZIF-8的载入不仅提高了膜材料的渗透通量,而且对不同价态的盐离子的去除都有较好的普适性。(2)同样采用层层自组装技术,在超滤膜表面负载金属有机骨架材料ZIF-8,制备金属有机骨架超滤膜。在终端过滤系统中考察其对天然有机物腐殖酸、蛋白质以及两者混合液的抗污染性能。研究发现金属有机骨架超滤膜的渗透通量较PES膜相比,提高幅度高达47%(82.18 L.m-2.h-1提高至120.78 L m-2·h-1)。并进行了腐殖酸、蛋白质及两者混合溶液的过滤试验,结果表明J/Jo的下降趋势随着ZIF-8的载入及其浓度增大得到明显缓解,表明所制备的金属有机骨架超滤膜对有机污染有着较好的抗污染性能。用GPC测定滤液中腐殖酸分子的大小及其分布,结果表明较大分子量的腐殖酸分子与较小分子量相比更容易被去除,且金属有机骨架超滤膜经过去离子水清洗和化学清洗之后,纯水通量恢复率高达84.5%和95.9%。而PES膜的纯水通量恢复率仅为49.5%和60.8%,表明制备的金属有机骨架超滤膜对有机污染具有较好的可逆性。(3)通过XDLVO热力学计算可知,金属有机骨架超滤膜与有机污染物之间的总自由能为正值,有利于缓解及抑制膜污染,当复合膜被污染之后,由于表面沉积了较疏水的腐殖酸,其zeta电位虽略微增大,但依旧为负值,依旧展示出了较好的抗污染性能。
[Abstract]:As a kind of new modern separation technology, membrane separation technology, both of the impurities and contaminants in the wastewater are effectively intercepted and removed, and the water can be recycled using material, also has the advantages of energy saving, no two pollution, simple operation, high efficiency, so it is widely application and promotion in water treatment technology. But the separation problem of membrane fouling in membrane technology is inevitable, membrane fouling is often in the form of flux decline, the reduction of separation efficiency. Energy consumption will lead to increased membrane service life greatly reduced, thus increasing the processing cost. Therefore membrane material preparation has a good anti the performance of pollutants in wastewater treatment, desalination and other fields is of great significance. This thesis focuses on the organic pollution of membrane separation technology in the process of seawater desalination and low efficiency problem in the membrane, with metal The organic skeleton ZIF-8 as loading material, layer by layer self assembly technology (LBL) was prepared with metal organic framework compound film material with high flux and good anti pollution performance, in the forward osmosis composite membrane system in the evaluation of the prepared on desalination performance of composite membrane material prepared for natural organic the contaminants in the system terminal filtration (NOM) anti pollution performance and using the analytic theory of XDLVO anti pollution mechanism. The main research contents and results are as follows: (1) using self-assembly technique, in forward osmosis membrane surface load of metal organic frameworks ZIF-8, preparation of metal organic frameworks and the use of forward osmosis membrane. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and X ray spectrometer (XPS) characterization means that the membrane materials have been successfully prepared, ZIF-8 has been in the forward osmosis membrane surface to form a continuous good symbiosis In the film, and the membrane surface becomes more rough. Contact angle test showed that the metal organic framework of forward osmosis membrane with smaller contact angle, FO film exhibits good hydrophilicity with respect to, so as to prevent pollutants in the deposition of material surface, adhesion and adhesion and penetration. In the device, the test is a metal organic framework osmosis membrane suitable for different valence ions removal, were selected for KC1, NaCl, MgCl2 and CaCl2 as the driving fluid, deionized water as raw water. When the load is 0.5% ZIF-8 (w/v), membrane water flux increased from 20LMH to 31LMH, increased 55%. and compared to FO the film shows the reverse salt flux is low, salt ions with different valence states have better retention effect. The results showed that ZIF-8 load can not only improve the permeation flux of membrane material, and the removal of salt ions with different valence states have good Universality. (2) using the same self-assembly technique in the load, the metal organic framework material ZIF-8 ultrafiltration membrane, preparation of metal organic framework ultrafiltration membrane. To study the natural organic matter and humic acid in the system terminal filter, anti pollution performance of protein and the mixture of the two liquid. It was found that the permeation flux of metal organic frameworks ultrafiltration membrane than the PES film compared to increase up to 47% (82.18 L.m-2.h-1 L m-2 increased to 120.78 h-1). And humic acid, protein and their mixture solution filtration experiments, the results showed that J/Jo decreased with the increase of the concentration of ZIF-8 loading and improved, indicate that the preparation of metal organic frameworks the ultrafiltration membrane has better anti pollution performance of organic pollution. Determination of the size and distribution of humic acid in the filtrate by GPC, results showed that humic acid molecules with large molecular weight smaller molecules Compared to the more easily removed, and the metal organic framework of ultrafiltration membrane after cleaning and chemical cleaning of deionized water, pure water flux recovery rate as high as 84.5% and 95.9%. while the pure water flux of PES membrane recovery rate was only 49.5% and 60.8%, showed that the metal organic frameworks prepared by ultrafiltration membrane on organic pollution has better reversibility. (3) by XDLVO thermodynamics, total free metal organic framework between super membrane and organic pollutants can be positive, to relieve and inhibit membrane fouling, when the composite membrane is polluted, due to the surface deposition of humic acid is hydrophobic, the zeta potential is increased slightly, but still negative, the show is still the better anti pollution performance.

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893;P747;X505

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