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离子分离重组技术在水淡化中的应用基础研究及功能性离子析分膜的制备
其他题名化学工程
张宇菲
学位类型硕士 ; 学位论文 ; 硕士 ; 学位论文
导师纳滤 ; 电渗析 ; 高水回收率 ; 阴离子交换膜 ; 层层自组装
2017-05
学位授予单位中国科学院大学
学位授予地点北京
学位专业摘 要 膜过程淡化技术已广泛应用于水收集、海水淡化与废水资源化等领域,其中 应用较为广泛的膜过程包括纳滤(NF)、反渗透(RO)、电渗析(ED)等技术。 本文主要针对膜过程处理技术在处理含高盐离子且浓缩时易结垢的水质过程中 出现的问题,不仅从工艺方面提出了新的 NF 与 ED 联用的离子分离重组技术 (Fractionation and metathesis = Fracsis),即 Fracsis 工艺,也从离子析分的原理 进行了进一步研究,制备了功能性离子析分膜来提高电渗析的离子分离性能。在 工艺技术上,我们利用了 NF 膜能够有效将一二价离子分离的特性来将二价离子 全部截留在浓缩水中,随后将纳滤产水和浓缩水分别通入 ED 的不同腔室,在电 场作用下,阴阳离子分别迁向相反方向,从而获得高溶解性盐,提高水回收率。 接下来,针对目前商用离子交换膜选择分离性较低,难以达到更好的离子析分效 果这一现状,本课题开发了拥有更高选择分离性的离子析分膜的制备方法。该方 法采用传统制备纳滤膜的层层自组装的方法来对商业离子交换膜表面改性,制备 出不同层数聚电解质的膜层,来提高阴膜的离子选择性。除此以外,本论文还利 用层层自组装制备出的高选择性离子交换膜,深入研究了一二价离子在膜中迁移 的限域传质作用。通过本研究得出如下结论: (1)Fracsis 技术中,纳滤 NFS 型号膜在三种不同 pH 值溶液中 Ca 2+ 的截留 率均大于 98%,达到了二价离子与一价离子分离的目的。在 ED 重组过程中,二 价离子重新与单价离子结合重组为具有高溶解度的盐。在 ED 的脱盐作用后获得 的水回收率高于不结垢时 RO 系统的理论值,在 pH = 4 体系中达到了 80%。而 通过理论计算,整个 Fracsis 系统的水回收率最高能达到的理论值为 98.5%。 对 Fracsis 系统采用间歇式操作,其能量消耗是 4.2 - 4.8 元/m 3 。该能耗有望 通过优化操作参数、扩大规模化、安装能量回收装置操作来进一步降低能耗。 Fracsis 系统的应用对于提高水回收率、减少污泥的产生和处理费用方面有突出优 势,且有望应用到有机或无机盐的合成和浓缩过程中。 (2)本课题通过简便、灵活的层层自组装的方法对离子交换膜表面进行修 饰,制备出具有单价离子选择性的阴离子交换膜。基膜的一二价离子选择性为1.0,而商业的 ACS 型号膜的选择性为 4.5。随着镀层层数的增加,膜对 Cl - 和 SO 4 2- 的选择性逐渐增加,当镀层数大于 5.5 层时选择性好于 ACS 膜。 同时,改性后的膜对有机酸的分离性能也有了提升。镀层后的膜对有机物的 选择性略高于 ACS 膜,且随着镀层的增加镀层膜对甲酸和正己酸的选择性也逐 渐提高,当层数达到 20.5 层时,膜对有机物的选择性则不再提升。随着镀层的 增加,膜的吸水性和膜的电阻值均逐渐增加,但是均低于 ACS 膜。层层自组装 的方法制备了可调控的膜面电荷及膜层致密度的膜,从而为实现离子、有机酸的 分离提供了简单可控的制备方法。 由于本课题中所用的聚电解质溶剂均为水相,使得该方法成为一种绿色环保 的膜表面修饰技术。制备得到的具有单价离子选择性的离子交换膜可应用在环保、 化工以及分离等行业。
关键词膜过程与膜制备
摘要中文
其他摘要Abstract Currently available fresh water is very scarce in global surface and groundwater. Seawater desalination, collection and wastewater reuse are the only way to solve the shortage of water resources. Membrane processes desalination technology has been widely used in many fields and expanding, which has been widely applied process including nanofiltration (NF) and reverse osmosis (RO), electrodialysis (ED), and other technologies. Aiming at the deficiency of membrane technologies in water desalination process, such as desalinating high salt and easily scaling water will arise the problem of membrane fouling. This study not only from the aspects of technology, put forward a new process: NF and ED combination (namely Fracsis) for ion separation and recombinant, but also did a further research about the principle of ion separation: preparing the functional membrane to improve the ion separation performance of electrodialysis. First, the NF membrane can effectively separate almost the bivalent ions into the condensed solution, then put the desalinated and concentrated solution into the different chambers of ED. Under the electric field, the ions of cations and anions were moving towards the opposite direction, so as to obtain high salt solubility, improving the water recovery. After that, in the process of preparation of ion exchange membrane, the traditional method for preparing nanofiltration membrane, layer-by-layer self-assembly was used to modified commercial anion exchange membrane surface, preparing the different layers of polyelectrolyte membrane, to improve the ion selectivity of anion exchange membrane. The following conclusions were got through this paper study: (1) In Fracsis process, the NFS membrane obtained a high rejection for Ca 2+ , all were above 98% in three pH systems, effective separation for bivalents. In ED metathesis experiment, bivalent ions recombined with monovalent ions obtaining high solubility salts. The water recovery rate after ED is higher than the theoretical value no fouling in RO system, reached 80% in pH = 4 system. And through the theoretical calculation, the Fracsis system can reach the highest in the theoretical value of 98.5%. The energy consumption of Fracsis system had carried on a simple calculation. The energy consumption of the batch operation system was 4.2 to 4.8 RMB/m 3 . The energy consumption is expected to further reduce through optimizing operation parameters, expand the scale, installation of energy recovery device. Fracsis system have prominent advantages for improving water recovery, reduce the sludge production and the processing costs, which is expected to be applied to the synthesis of organic or inorganic salt and the enrichment process. (2) This research used simple and flexible method of layer-by-layer self-assembly to modify the anion exchange membrane surface, prepared one kind of thin-film composite anion exchange membrane with high ion selectivity for Cl - and SO 4 2- . The ion selectivity of base membrane was 1.0, and the increased with the layers number. When modified by 5.5 layers, the selectivity was better than the commercial ACS membrane with the value of 4.5. Another hand, the modified anion exchange membranes were also evaluated by the performance of separated organic acids. In the ED experiment, with the increase of coating layers, the water contents and membrane resistance were gradually increasing, but both lower than the ACS membrane. A trend was obviously observed that doping graphene would reduce the membrane resistance. Layer-by-layer methods can regulate the surface charge density of the membrane and the dense layer, thus providing a simple and controllable preparation method to achieve the separation of the ions, organic acids. Due to the polyelectrolytes both were dissolved into water phase, making the method as one kind of green environmental technology to modify the membrane surface. This kind of TFC-AEM with monovalent ion selective separation for monovalent and organic can be used in environmental protection, chemical industry, separation and other fields.
作者部门环境资源化与水回用团队
公开日期2017-06-30
学位类型硕士 ; 学位论文 ; 硕士 ; 学位论文
语种中文
文献类型学位论文
条目标识符http://ir.qibebt.ac.cn/handle/337004/9985
专题环境资源化与水回用团队
作者单位中国科学院大学
推荐引用方式
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张宇菲. 离子分离重组技术在水淡化中的应用基础研究及功能性离子析分膜的制备[D]. 北京. 中国科学院大学,2017.
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