氧化石墨烯基正渗透膜的制备及其分离性能的研究

发布时间：2018-06-09 00:29

本文选题：氧化石墨烯层状膜 + 多孔氧化石墨烯　；参考：《中国科学院研究生院(上海应用物理研究所)》2017年硕士论文

【摘要】：氧化石墨烯(GO)作为单原子层厚度的新型二维纳米材料,具有优异的机械性能、超高的比表面积及结构稳定性。氧化石墨烯层状膜具有较好的水渗透能力及溶质截留选择性,是理想的分离膜材料,近年来,其在海水淡化、水/有机溶剂分离及气体分离等领域的应用研究引起了广泛关注。正渗透技术是以半透膜两侧溶液的渗透压差作为驱动力的新型膜分离技术,相对传统膜技术而言,具有低能耗、低膜污染、高回收率及零排放等优点,是当前膜分离技术领域的研究热点之一。然而,常规结构的正渗透膜因受内浓差极化及溶质反向渗透等现象的影响,膜的水通量及分离效率显著下降,这一技术难题限制了正渗透技术的实际应用。因此,研究新型结构的正渗透膜,降低内浓差极化和溶质反向渗透效应对膜分离性能的影响,对正渗透技术的应用推广具有重要的意义。本论文将GO和多孔GO作为起始材料,通过真空抽滤-热致交联法,制备了不同结构的氧化石墨烯基正渗透膜,并系统地评价了其在正渗透过程中的分离性能。主要研究内容包括以下两个方面:其一,超薄无支撑氧化石墨烯层状膜的制备及其在正渗透分离过程中的性能研究。通过真空抽滤-热致交联法制备得到厚度约1μm的超薄无支撑氧化石墨烯层状(UFGOL)膜。经化学结构分析表明,膜内GO片层与丙二酸发生了酯化交联反应,并在热处理过程中发生了部分还原;UFGOL膜的干、湿态XRD测试结果显示,丙二酸的交联作用有助于缩小氧化石墨烯层状膜的层间距及提高在水溶液中的结构稳定性。通过正渗透分离性能测试得出,以2 mol L~(-1) Na Cl溶液作为汲取液,纯水为料液时,UFGOL膜的水通量达35 L m~(-2)h~(-1),而对Na~+的返盐率仅0.56 mol m~(-2)h~(-1)。通过对比发现,带有支撑层的氧化石墨烯层状膜的水通量仅为13.4 L m~(-2)h~(-1),说明正渗透过程中的内浓差极化效应对UFGOL膜渗透性能的影响被大幅减弱。经正渗透有机染料及重金属离子溶液分离实验发现,UFGOL膜能够完全截留有机染料分子(如甲基橙,罗丹明B)及重金属离子(如Cu~(2+)),表现出较好的净水性能。其二,辐照刻蚀法制备多孔氧化石墨烯,及多孔氧化石墨烯层状复合膜的制备与正渗透分离性能研究。利用伽马射线的辐解产物——HO·自由基在GO片层面内及边缘处的刻蚀反应,得到纳米尺度、孔径可控的多孔GO片层,并对HO·自由基的刻蚀行为和机理进行了深入分析,发现GO片层上的含氧基团是HO·自由基的主要进攻位点,刻蚀部位的C、O原子变成CO_2或CO,而形成孔洞结构,且可通过控制反应体系的吸收剂量,调控片层面内孔径分布。以多孔GO为起始材料,通过真空抽滤-热致交联法制得多孔氧化石墨烯层状复合(PGOLC)膜,接触角及XRD测试结果表明,辐照刻蚀后得到的多孔GO制备的PGOLC膜的亲水性得到提高,而丙二酸的酯化交联作用能够有效地减小复合膜在湿态条件下层间距的扩张,提高结构稳定性。经正渗透分离性能测试,以1 mol L~(-1)蔗糖溶液作为汲取液,超纯水为料液,PGOLC膜的水通量高达34.7L m~(-2)h~(-1),而未经刻蚀处理的氧化石墨烯层状膜的水通量仅为14.2 L m~(-2)h~(-1)。经正渗透有机染料罗丹明B溶液分离测试发现,PGOLC膜的水通量可达21.7 L m~(-2)h~(-1),而未经刻蚀处理的氧化石墨烯层状膜降为6.7 L m~(-2)h~(-1),由此可见,以多孔GO制备的PGOLC膜的渗透性能远优于普通氧化石墨烯层状膜。原因在于,多孔GO上的纳米孔道为水分子的渗透提供了更多的纵向通道,缩短了层状膜内的传递路径。本论文中,通过自组装-热致交联法制备超薄无支撑氧化石墨烯层状膜,有效地减弱了正渗透过程中内浓差极化对层状膜水通量的影响,为新型正渗透膜的研究提供了新的研究思路;同时利用辐射刻蚀法制备多孔GO,并以此制得具有更高渗透性能的多孔氧化石墨烯层状复合膜,为制备高性能氧化石墨烯基正渗透膜的研究提供了新的技术路线。
[Abstract]:Graphene oxide (GO), a new two-dimensional nanomaterial with the thickness of the single atomic layer, has excellent mechanical properties, super high specific surface area and structural stability. The graphene oxide layered membrane has good water permeability and solute interception selectivity. It is an ideal separation membrane material. In recent years, it has been used in seawater desalination, water / organic solvent separation. The application of gas separation and other fields has attracted wide attention. The positive permeation technology is a new membrane separation technology using the osmotic pressure difference of the semi permeable membrane as the driving force. Compared with the traditional membrane technology, it has the advantages of low energy consumption, low membrane pollution, high recovery rate and zero emission. It is a hot topic in the field of membrane separation technology. However, the water flux and separation efficiency of the membrane are significantly reduced due to the effects of internal concentration polarization and reverse osmosis of the solute. This technical problem restricts the practical application of the positive osmosis technology. Therefore, the study of the new structure of the positive permeable membrane has been made to reduce the internal consistency and solute reverse osmosis effect to the membrane separation. The effect on the performance is of great significance to the application and popularization of the positive osmosis technology. In this paper, GO and porous GO are used as starting materials to prepare different structures of graphene based positive osmosis membranes by vacuum pumping and thermally induced crosslinking, and the separation performance in the positive permeation process is evaluated systematically. The main contents include the following The two aspects: first, the preparation of ultrathin non supporting graphene oxide lamellar membrane and its performance in the process of positive osmosis separation. The ultrathin non supporting graphene oxide layered (UFGOL) films with thickness about 1 m were prepared by vacuum pumping thermal crosslinking method. The chemical structure analysis showed that the GO lamellar layer in the membrane was esterified with malonic acid. A partial reduction was made in the process of heat treatment, and the dry and wet XRD test results of UFGOL film show that the crosslinking effect of malonic acid helps to reduce the interlayer spacing of the graphene oxide layered film and improve the structural stability in aqueous solution. Through the test of positive permeability separation performance, 2 mol L~ (-1) Na Cl solution is used as a drawing solution. When pure water is a liquid, the water flux of UFGOL film reaches 35 L m~ (-2) h~ (-1), while the rate of return to Na~+ is only 0.56 mol m~ (-2) h~ (-1). By contrast, the water flux of the layered film with the supporting layer is only 13.4. It is found that the UFGOL membrane can completely intercept the organic dye molecules (such as methyl orange, Luo Danming B) and heavy metal ions (such as Cu~ (2+)) through the separation of positive osmosis organic dyes and heavy metal ions. Second, the preparation of porous oxide graphene by irradiation etching and the preparation of porous graphite oxide layered composite film Study on the separation performance of the preparation and the positive osmosis. Using the etching reaction of the gamma ray radiolysis product, HO free radical in the GO slice and the edge, the porous GO lamellae with nano scale and controllable pore size are obtained. The etching behavior and mechanism of the HO free radical are deeply analyzed. It is found that the oxygen group on the GO layer is the master of the HO free radical. In order to attack the site, the C of the etching site, O atom becomes CO_2 or CO, and the pore structure is formed, and the pore size distribution in the slice can be controlled by controlling the absorbed dose of the reaction system. Porous GO is used as the starting material to obtain the porous graphite oxide layered composite (PGOLC) film by vacuum pumping thermal crosslinking method. The contact angle and the XRD test results show that the porous GO is the starting material. The hydrophilicity of the PGOLC film prepared by the porous GO after irradiation is improved, and the esterification and crosslinking of malonic acid can effectively reduce the expansion of the interlayer spacing under the wet condition and improve the structural stability. The 1 mol L~ (-1) sucrose solution is used as the drawing liquid through the positive permeation separation performance test, and the super pure water is the liquid and PGOLC film. The water flux is as high as 34.7L m~ (-2) h~ (-1), while the water flux of the untreated graphene oxide layer membrane is only 14.2 L m~ (-2) h~ (-1). It is found that the water flux of the PGOLC membrane is up to 21.7. The water flux in the Luo Danming B solution of the positive osmosis organic dye is found to be up to 6.7 It can be seen that the permeability of PGOLC films prepared with porous GO is much better than that of the ordinary graphene oxide lamellar membrane. The reason is that the nano pore on the porous GO provides more longitudinal channels for the permeation of water molecules and shortens the transmission path in the layered membrane. In this paper, the self assembly and thermally induced crosslinking method is used to prepare the ultra-thin and unsupported oxidation. Graphene layered film effectively weakens the influence of internal consistency polarization on the water flux of layered membrane during the process of positive infiltration. It provides a new research idea for the study of new type of positive permeable membrane. At the same time, the porous GO is prepared by radiation etching, and the porous multi porous graphite oxide layered composite membrane with higher permeability is prepared to prepare high performance. The study of graphene oxide based permeable membranes provides a new technological route.
【学位授予单位】：中国科学院研究生院(上海应用物理研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893

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