用于光催化水处理的平板微流控系统研究

发布时间：2018-01-10 20:36

本文关键词：用于光催化水处理的平板微流控系统研究　出处：《中国科学院长春光学精密机械与物理研究所》2017年博士论文　论文类型：学位论文

【摘要】：近年来,以光学和流体力学为基础的微流控技术得到了迅速发展,在生物医学、医疗保健、环境保护等方面都有着广泛的应用前景。随着工业生产日益发达,水污染的问题日益严峻,生产和生活对纯水的需求量越来越大,微流控技术在水处理应用领域也随之发展。如何净化水资源,以及怎样提高污水的净化效率是当务之急。光催化反应能最大限度的利用自然界中的太阳光能,在节约能源、提高效率方面比起其他化学反应有更大的优势。在利用光催化技术对水质进行净化处理的反应体系中,基于微流控技术的微反应器和基于半导体材料的光催化剂对反应效率起到了举足轻重的作用。本文从优化微反应器结构和改良半导体光催化剂入手,希望从这两方面同时提高光催化水处理的效率。在微通道反应器的设计方面,本课题从自然界中得到灵感,结合仿生设计,利用Murray’s law及其推广公式设计了一种平板多级树形微通道。这种通道可以使通道切面剪应力一致,且能量损失最小。在设计出仿生微通道结构后,通过有限元分析软件COMSOL Multiphysics模拟了流体在微通道中的流动性质,并比较了流体在仿生和非仿生微通道中的流动情况,从流速和压降的变化情况可知,仿生微流控系统均优于非仿生微流控系统,验证了设计的正确性。同时,在仿生微流系统和非仿生微流控系统的反应区域建立了一个理想的光催化反应模型,证实了仿生设计可以提高微流控系统的稳定性和光催化效率。此外,我们研究了微通道中的毛细力现象,并通过仿真分析了毛细力的一些规律,再用实验来证实,仿真和实验结合的很好。在工艺选择方面,利用微纳工中的软光刻技术,用PDMS制作平板仿生微通道反应器,并与非仿生反应器的光催化效率进行比较,实验得出仿生反应器的催化效率高于非仿生微通道反应器,最高时效率能提高68%,与模拟趋势一致,结果相符。在光催化剂的研究方面,本文利用水热法制备出了大比表面积的TiO2微球,增大了光催化剂与反应物的接触面积。另一方面,我们利用某些重金属离子在纳米级别或亚微米级别会表现出表面等离子共振的特性,用化学合成方法将纳米级别的Au颗粒负载在Ti O2微球表面。负载在半导体表面的Au表现出非常活泼的性质,具有很强的得电子能力,并能帮助TiO2吸收更宽谱段的光能,使光催化剂对太阳光的吸收谱段从~400nm提高到~900nm,使TiO2在可见光波段的吸收率和量子效率大大提高。同时也通过实验证明,负载Au颗粒的Ti O2微球在微通道降解的过程中效率远远大于未负载Au颗粒的TiO2微球,在每一个时间段效率都可提高3倍以上。
[Abstract]:In recent years, microfluidic technology based on optics and hydrodynamics has been developed rapidly, and has been widely used in biomedicine, medical care, environmental protection and so on. The problem of water pollution is becoming more and more serious, the demand for pure water is increasing in production and daily life, and the microfluidic technology has been developed in the field of water treatment. How to purify water resources. And how to improve the efficiency of sewage purification is an urgent matter. Photocatalytic reaction can maximize the use of solar energy in nature, in energy conservation. Higher efficiency than other chemical reactions in the use of photocatalytic technology to purify the water in the reaction system. Microreactors based on microfluidic technology and photocatalysts based on semiconductor materials play an important role in the reaction efficiency. This paper starts with optimizing the structure of microreactors and improving semiconductor photocatalysts. It is hoped that the efficiency of photocatalytic water treatment can be improved from these two aspects. In the design of microchannel reactor, this subject is inspired by nature and combined with bionic design. Using Murray's law and its extended formula, a multilevel tree-shaped microchannel is designed, which can make the shear stress of the channel plane consistent. After designing the bionic microchannel structure, the fluid flow in the microchannel was simulated by the finite element analysis software COMSOL Multiphysics. The fluid flow in bionic and non-bionic microchannels is compared. From the variation of velocity and pressure drop, the bionic microfluidic system is superior to the non-bionic microfluidic system, which verifies the correctness of the design. An ideal photocatalytic reaction model is established in the reaction region of bionic microfluidic system and non-bionic microfluidic system. It is proved that bionic design can improve the stability and photocatalytic efficiency of the microfluidic system. We studied the capillary force phenomenon in the microchannel, and analyzed some laws of capillary force by simulation, and proved by experiment that the combination of simulation and experiment is very good. The plate bionic microchannel reactor was fabricated by using the soft lithography technology of micronanotechnology and PDMS, and the photocatalytic efficiency of the bionic reactor was compared with that of the non-bionic reactor. The results show that the catalytic efficiency of bionic reactor is higher than that of non-bionic microchannel reactor, and the maximum efficiency can be increased by 68%, which is consistent with the simulation trend. In this paper, TiO2 microspheres with large specific surface area were prepared by hydrothermal method, which increased the contact area between photocatalyst and reactant. We use some heavy metal ions to exhibit surface plasmon resonance at nanometer or submicron level. Au nanoparticles were loaded on the surface of TIO 2 microspheres by chemical synthesis. Au loaded on semiconductor surface showed very active properties and had strong electronic ability. It can also help TiO2 absorb the light energy in a wider spectrum and increase the absorption spectrum of photocatalyst from 400nm to 900nm. The absorptivity and quantum efficiency of TiO2 in visible wavelength are greatly improved. The efficiency of TiO2 microspheres loaded with au particles was much higher than that of TiO2 microspheres without au particles in the process of microchannel degradation, and the efficiency could be increased by more than three times in every time period.
【学位授予单位】：中国科学院长春光学精密机械与物理研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X703;O643.36

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