氮化硅基陶瓷膜的制备及膜蒸馏应用研究

发布时间：2018-08-19 15:32

【摘要】：随着世界人口的增长和工业化水平的提高,人们在对能源不断索取之余,淡水资源这一人类生存必需品也列入各国争取的目标。在天灾、人为等因素的影响下,本就储量很少的淡水资源更加匮乏,非洲、中东地区尤为严重。我国部分省市也长期处于干旱情况,严重地区已经影响到人民的日常饮用水问题。解决水资源问题迫在眉睫。海水淡化技术是一种有效获得淡水资源的工艺,庞大的海水资源为海水淡化提供了足够的原材料。在二十世纪中期开始使用以来获得蓬勃发展,美国在1954年建成的海水淡化工厂至今仍在运行,源源不断的提供着日常用水。近年来,海水淡化工业在中东地区发展迅速。蓬勃的石油交易为其提供了大量的研究资金，极度水资源匮乏也迫使当地人投入大量人力物力来发展海水淡化这一淡水资源开源增量工程。膜蒸馏过程是一种有效的海水淡化工艺,但是自从1963年被人发现以来,依旧未完全在工业中实施。最近,膜蒸馏膜工程(比如膜的设计、制备和膜蒸馏性能测试)越来越受到大家的关注,膜蒸馏技术发展迅速。膜蒸馏技术的关键点就是分离膜材料的研究,寻找一种有效、高效、长效的分离膜蒸馏膜材料是其发展的重中之重。本文的宗旨是探索一种能够稳定运行的有发展潜力的膜材料,在前人的研究中了解到,有机膜在高温海水这种环境下稳定性存在问题,基于本实验室的前期研究成果,本文研究重点为高度稳定的非氧化物陶瓷膜。分别从陶瓷膜的制备、表面修饰改性、膜蒸馏性能等方面进行稳定膜蒸馏用陶瓷膜的探索。具体分为以下几个部分。第一章介绍当前水资源现状,淡水需求的迫切性；海水淡化工艺的工业化情况及当前海水淡化工艺的缺陷；膜蒸馏技术的工作原理及阻碍膜蒸馏工艺实现工业化的障碍；陶瓷膜的制备及改性方法。最后阐述了整个研究思路。第二章简单介绍了实验过程中用到的原料和仪器。第三章介绍两部分的研究：一是β-Sialon陶瓷纤维管膜的成型和烧结。使用相转化挤出成型配合烧结的方法成功获得纤维管膜,通过有效浆料中分散剂种类、含量和浆料组分配比获得稳定均一的浆料,并且通过调节烧结温度等条件对陶瓷膜的性质进行了表征和优化；二是氮化硅和β-Sialon陶瓷平板膜制备和表征。使用相转化流延和烧结的放法制备了氮化硅平板膜。通过优化陶瓷膜的浆料配比、烧结温度等条件,成功获得了高强度和高孔隙率的氮化硅和β-Sialon陶瓷平板膜。第四章介绍陶瓷膜的表面修饰改性,并且对于已经改性好的陶瓷膜进行膜蒸馏过程测试。陶瓷膜的天然亲水性使其不适用于膜蒸馏过程,其表面改性过程是提高其使用寿命,使其具有投入工业生产淡水潜力的一个关键步骤,主要包括三种改性方法：(1)表面嫁接氟硅烷分子；(2)表面氯硅烷氨解聚合热解无机纳米颗粒修饰；(3)表面聚二甲基硅氧烷热解修饰。三种修饰方法都成功达到表面改性的目标,并且都在膜蒸馏过程中具有分离作用获得了纯水。但是其长期稳定性却不相同,氟硅烷有机分子嫁接稳定性明显劣于热解修饰。第五章在获得稳定实用的陶瓷膜基础上尽可能的提高陶瓷膜膜蒸馏的通量。通过改进陶瓷膜的成型过程,使用石墨牺牲层的双层流延以及热压工艺,有效地提高了陶瓷膜的物质传输通量,使膜蒸馏过程中的水通量提高了50%以上。提高了陶瓷膜膜蒸馏过程的效率,使其工业化应用更进一步。第六章介绍氮化硅陶瓷在其作为支撑体材料的一种应用,在氮化硅中空纤维管膜的外表面成功合成了一层致密的ZIF-8气体分离膜,并且证明了其在二氧化碳吸附和分离方面的应用。氢气和二氧化碳的分离因子为11.67。第七章对本文的工作进行了总结,并且指出了工作的不足之处和发展前景。
[Abstract]:With the growth of world population and the improvement of industrialization level, people are constantly demanding energy, freshwater resources as a human survival necessities are also included in the goals of all countries. The long-term drought has affected people's daily drinking water problems in serious areas. It is urgent to solve the problem of water resources. Seawater desalination technology is an effective way to obtain fresh water resources. The huge seawater resources provide sufficient raw materials for seawater desalination. In recent years, the desalination industry has developed rapidly in the Middle East. The booming oil trade has provided it with a large amount of research funds. The extreme shortage of water resources has also forced the local people to invest a lot of manpower and resources to develop desalination. Membrane distillation process is an effective seawater desalination process, but it has not been fully implemented in industry since it was discovered in 1963. Recently, membrane engineering (such as membrane design, preparation and performance testing of membrane distillation) has attracted more and more attention, and membrane distillation technology has developed rapidly. The key point of distillation technology is the study of membrane materials. It is very important to find an effective, efficient and long-term membrane material for membrane distillation. Based on the previous research results of our laboratory, this paper focuses on highly stable non-oxide ceramic membranes. The preparation of ceramic membranes, surface modification, membrane distillation performance and other aspects of stable membrane distillation ceramic membranes are explored. It is divided into the following parts. The first chapter introduces the current situation of water resources, light. The urgency of water demand, the industrialization of seawater desalination process and the shortcomings of current seawater desalination process, the working principle of membrane distillation technology and the obstacles hindering the industrialization of membrane distillation process, the preparation and modification methods of ceramic membranes are described. Finally, the whole research idea is elaborated. Materials and instrumentation. Chapter 3 introduces the study of two parts: one is the formation and sintering of the membrane of the beta-Sialon ceramic fibers. Fiber membranes are successfully obtained by phase inversion extrusion molding with sintering. The stable and uniform slurry is obtained by the type, content and proportion of dispersants in the effective slurry, and the sintering temperature is adjusted. Silicon nitride and beta-Sialon ceramic flat membranes with high strength and high porosity were successfully obtained by optimizing the slurry ratio and sintering temperature. In the fourth chapter, the surface modification of ceramic membrane is introduced, and the membrane distillation process is tested for the modified ceramic membrane. The natural hydrophilicity of ceramic membrane makes it unsuitable for membrane distillation process. The surface modification process is a key step to improve its service life and make it have the potential of industrial production of fresh water. Suddenly, there are three modification methods: (1) surface grafting of fluorosilane molecules; (2) surface modification of chlorosilane pyrolysis pyrolysis pyrolysis inorganic nanoparticles; (3) surface polydimethylsiloxane pyrolysis modification. All three modification methods have successfully achieved the goal of surface modification, and all of them have the separation effect in the process of membrane distillation to obtain pure water. The grafting stability of fluorosilane is obviously inferior to that of pyrolysis modification. In the fifth chapter, the distillation flux of ceramic membrane is increased as much as possible on the basis of obtaining stable and practical ceramic membrane. The material transfer flux of ceramic membrane was increased by more than 50% during membrane distillation. The efficiency of membrane distillation was improved and the industrial application was further improved. In chapter 6, silicon nitride ceramics was successfully synthesized on the outer surface of silicon nitride hollow fiber tube membrane. The dense ZIF-8 gas separation membrane has been proved to be suitable for carbon dioxide adsorption and separation. The separation factors of hydrogen and carbon dioxide are 11.67. Chapter 7 summarizes the work in this paper and points out the shortcomings and prospects of the work.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ051.893

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