碳量子点修饰半导体复合材料的制备及可见光下处理偶氮染料废水的研究

发布时间：2018-04-19 15:15

本文选题：量子 + 修饰　；参考：《江苏大学》2017年硕士论文

【摘要】：偶氮染料是当今种类最多、使用最广泛的一类染料。但是在生产和应用过程中,高达10%-15%的染料未经处理就被排放到环境中,对人类的生活和健康造成了巨大威胁。因此,排放前对其进行无害化处理是目前控制偶氮染料废水污染的最好方法。目前,传统的处理偶氮染料废水的方法效果不佳,在处理偶氮染料污染的同时,可能会造成更为严重的环境危机(例如活性泥法,在厌氧条件下可能会生成对人类危害更大的芳香胺类物质)。因此,人们迫切需要寻找一种高效、清洁、可持续的方法来解决偶氮染料废水问题。在这种背景下,半导体光催化技术走进了人们的视野。然而光生电子-空穴对分离不彻底、电子和空穴复合率高等缺点在一定程度上限制了单一半导体光光催化剂的活性。为了解决上述问题,该工作选用一种新型的纳米碳材料(碳量子点)来修饰半导体光催化剂,希望能够大幅度的提升其对偶氮染料(甲基橙)的光催化降解活性。具体研究内容如下:(1)CQDs/ZnFe_2O_4复合材料是通过一种简单的超声波辅助法制备的。各种表征结果显示:ZnFe_2O_4微球被低对比度的碳量子点层包覆,形成了一种核壳结构。为了研究CQDs/Zn Fe_2O_4复合材料的光催化性能,我们以制备的复合材料为催化剂进行了光催化降解亚甲基蓝的研究,结果表明:当碳量子点的负载量为20%(质量分数)时,CQDs/ZnFe_2O_4复合材料的光催化性能最优,大约是纯Zn Fe_2O_4样品的5.9倍。基于固体紫外-可见吸收、荧光、阻抗等分析结果,我们提出了光催化活性提高的可能机理。(2)通过一步水热法合成了一种新型的碳量子点修饰In_2S_3微球光催化剂,与纯In_2S_3相比,该催化剂表现出优异的偶氮染料降解活性(120 mim内可以实现对甲基橙近90%的光催化降解)。通过大量的实验和表征,我们发现:碳量子点修饰In_2S_3微球光催化剂具有优异的光催化活性的主要原因是碳量子点的上转换荧光功能和优异的电子转移能力。基于捕获实验、电子顺磁共振分析、紫外-可见吸收和理论计算可以确定·O2-和h+是光催化过程中的主要活性物种,进而提出了可能的光催化降解机理。(3)该部分工作主要研究CQDs/Bi4O5I2复合材料在可见光下降解偶氮染料甲基橙的性能。为了更好的突出碳量子点修饰半导体光催化剂用于光催化降解偶氮染料废水的优势,我们选取并制备最具代表性的Bi2S3/Bi4O5I2复合材料与
[Abstract]:Azo dyes are the most widely used dyes in the world.However, in the process of production and application, up to 10- 15% of the dyes are discharged into the environment without treatment, which poses a great threat to human life and health.Therefore, it is the best way to control the pollution of azo dye wastewater before discharge.At present, the traditional treatment of azo dye wastewater is not effective, while the treatment of azo dye pollution may cause a more serious environmental crisis (such as reactive sludge process,Under anaerobic conditions, aromatic amines may be produced that are more harmful to humans.Therefore, there is an urgent need to find an efficient, clean and sustainable way to solve the azo dye wastewater problem.In this context, semiconductor photocatalytic technology into the field of vision.However, the separation of photogenerated electron-hole pairs is not complete, and the high recombination rate of electrons and holes limits the photocatalytic activity of a single semiconductor photocatalyst to some extent.In order to solve the above problems, a new nano-carbon material (carbon quantum dot) was chosen to modify the semiconductor photocatalyst. It is hoped that the photocatalytic degradation activity of azo dyes (methyl orange) can be greatly improved.The specific research contents are as follows: CQDs / ZnFe2O4 composites were prepared by a simple ultrasonic assisted method.The results show that the microspheres are coated with low contrast carbon quantum dots to form a core-shell structure.In order to study the photocatalytic properties of CQDs/Zn Fe_2O_4 composites, the photocatalytic degradation of methylene blue was studied.The results show that the CQDs / ZnFe2O4 composite has the best photocatalytic performance when the loading amount of carbon quantum dots is 20 (mass fraction), which is about 5.9 times as high as that of pure Zn Fe_2O_4.Based on the results of solid UV-Vis absorption, fluorescence and impedance analysis, we proposed a possible mechanism for the improvement of photocatalytic activity. A novel carbon quantum dot-modified In_2S_3 microsphere photocatalyst was synthesized by a one-step hydrothermal method. Compared with pure In_2S_3, a new type of photocatalyst was synthesized.The catalyst showed excellent degradation activity of azo dyes and could achieve nearly 90% photocatalytic degradation of methyl orange within 120 mim.Through a large number of experiments and characterization, we found that the main reasons for the excellent photocatalytic activity of carbon quantum dots modified In_2S_3 microspheres are the up-conversion fluorescence function and the excellent electron transfer ability of carbon quantum dots.Based on capture experiments, electron paramagnetic resonance analysis, UV-Vis absorption and theoretical calculations, it can be concluded that O _ 2- and h are the main active species in photocatalytic process.Furthermore, the possible photocatalytic degradation mechanism was proposed. (3) the main work of this part was to study the degradation of azo dye methyl orange by CQDs/Bi4O5I2 composites under visible light.In order to better highlight the advantages of carbon quantum dot-modified semiconductor photocatalysts for photocatalytic degradation of azo dye wastewater, we selected and prepared the most representative Bi2S3/Bi4O5I2 composites.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X791;O643.36

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