类石墨相氮化碳基复合纳米光催化体系构筑及可见光降解染料性能研究

发布时间：2018-04-22 06:24

本文选题：染料 + 水热法　；参考：《江苏大学》2017年硕士论文

【摘要】：随着经济与社会的发展,水资源污染越来越严重,染料的大量使用更是加剧了水资源的短缺。染料废水不仅对水资源造成严重破坏,对人体健康也构成一定的威胁。出于民生和发展角度来说,必须对染料废水进行严格的处理。除了避免染料废水的乱排放,还要利用有效的科学技术来解决当前已造成的染料污染。本文对目前国内外染料废水处理技术进行简单分析与归纳总结,提出了最近在环境与能源领域比较热点的光催化方法。光催化方法有高效、绿色环保、操作简单等优点,对未来解决有机物污染有着广阔的前景。具有适当的带隙、优异的稳定性和成本低等特点的非金属聚合物半导体氮化碳(g-C_3N_4)已经引起了科学家们广泛关注。然而,较低的量子效率极大地限制了g-C_3N_4的实际应用。可以将g-C_3N_4与合适的光催化剂复合构建异质结。异质结的形成有利于光生电荷的转移与分离,抑制光生电子和空穴的复合从而提高其量子效率。本论文采用水热法制备了g-C_3N_4/CdWO_4、MnWO_4/g-C_3N_4、g-C_3N_4/O-doped ZnIn_2S_4三种异质结并通过降解染料来评价其光催化效果。取得的成果主要有以下三个方面:(1)利用水热法制备了g-C_3N_4/CdWO_4纳米复合材料,通过一系列表征证明了棒状CdWO_4均匀地负载在层状g-C_3N_4表面。异质结的形成有利于g-C_3N_4表面光生电子和空穴的分离,让更多的活性物种参与有机物的氧化还原反应,从而提高其光催化活性。当异质结中CdWO_4的含量为20%时,复合材料表现出最好的降解效果,在180 min可见光下对罗丹明B的降解率为94%,表现出了很好的脱色效果。经过四次循环后,异质结对罗丹明B的降解没有明显地降低依,证明了异质结良好的稳定性。通过捕获实验和ESR表征实验我们提出了g-C_3N_4/CdWO_4的降解机理。(2)通过水热法合成了MnWO_4/g-C_3N_4纳米复合材料,通过一系列表征证明了花状MnWO_4均匀地负载在层状g-C_3N_4表面。当MnWO_4的负载量为10%时,复合光催化剂的活性最高,分别是纯g-C_3N_4和MnWO_4降解率的2.3倍和12.7倍。可见光下,10%MnWO_4/g-C_3N_4异质结在4 h可见光下内对罗丹明B的降解率为73%,表现出了很好的脱色效果,经过四次循环实验,异质结的光催化活性没有明显地降低,表现出了催化剂良好的稳定性,有利于工业应用。通过捕获实验和ESR表征实验我们提出了MnWO_4/g-C_3N_4的降解机理。(3)通过水热法制备了g-C_3N_4/O-doped ZnIn_2S_4纳米复合材料,通过XPS证明了Zn In_2S_4中晶格氧的存在。HRTEM验证了片状氧掺杂的Zn In_2S_4成功地负载在层状g-C_3N_4的表面。当g-C_3N_4的负载量为20%时,复合材料对罗丹明B表现出了最好的降解率。在20 min可见光下,20%g-C_3N_4/O-doped Zn In_2S_4对罗丹明B的降解率为97%,表现了很出色的降解效果,且在四次循环后降解效果没有明显地降低,体现了光催化剂良好的稳定性。
[Abstract]:With the development of economy and society, water pollution is becoming more and more serious. Dye wastewater is not only a serious damage to water resources, but also a threat to human health. From the point of view of people's livelihood and development, dye wastewater must be treated strictly. Besides avoiding the random discharge of dyestuff wastewater, effective science and technology should be used to solve the dyestuff pollution. In this paper, the dyeing wastewater treatment technology at home and abroad is simply analyzed and summarized, and the photocatalytic method which is a hot spot in the field of environment and energy is put forward in this paper. Photocatalytic method has the advantages of high efficiency, green environmental protection, simple operation and so on. It has broad prospects for solving organic pollution in the future. Non-metallic polymer semiconductors with suitable band gap, excellent stability and low cost have attracted much attention. However, low quantum efficiency greatly limits the practical application of g-C_3N_4. The heterojunction can be constructed by combining g-C_3N_4 with the appropriate photocatalyst. The formation of heterojunction is conducive to the transfer and separation of photogenerated charges and the inhibition of the combination of photogenerated electrons and holes to improve their quantum efficiency. In this paper, we have prepared g-C _ S _ 3N _ 3N _ 3N _ 3N _ 2O _ 4 / C _ 3N _ 3C _ 3N _ 3C _ 3N _ 3N _ 3C _ 3N _ 3N _ 3 heterojunction by hydrothermal method and evaluated its photocatalytic effect by the degradation of dyes. The main achievements are as follows: 1) g-C_3N_4/CdWO_4 nanocomposites were prepared by hydrothermal method. A series of characterization proved that rod-shaped CdWO_4 was uniformly loaded on the surface of layered g-C_3N_4. The formation of heterojunction is conducive to the separation of photogenerated electrons and holes on the surface of g-C_3N_4, and more active species are involved in the redox reaction of organic compounds, thus enhancing their photocatalytic activity. When the content of CdWO_4 in the heterojunction was 20, the composite showed the best degradation effect, and the degradation rate of Rhodamine B was 94 under 180 min visible light, showing a good decolorization effect. After four cycles, the degradation of Rhodamine B by heterojunction was not significantly reduced, which proved the good stability of the heterojunction. The degradation mechanism of g-C_3N_4/CdWO_4 was proposed by trapping experiment and ESR characterization experiment. (2) MnWO_4/g-C_3N_4 nanocomposites were synthesized by hydrothermal method. A series of characterization showed that the MnWO_4 was uniformly loaded on the surface of layered g-C_3N_4. When the loading amount of MnWO_4 is 10, the activity of the composite photocatalyst is the highest, which is 2.3 times and 12.7 times higher than that of pure g-C_3N_4 and MnWO_4, respectively. In the visible light, the degradation rate of Rhodamine B by 10MnWOS 4 / g-C3Nac 4 heterojunction was 73% under visible light for 4 h, showing a very good decolorization effect. After four cycle experiments, the photocatalytic activity of the heterojunction did not decrease significantly. The catalyst shows good stability and is favorable for industrial application. The degradation mechanism of MnWO_4/g-C_3N_4 was proposed by trapping experiment and ESR characterization experiment. (3) g-C_3N_4/O-doped ZnIn_2S_4 nanocomposites were prepared by hydrothermal method. The existence of lattice oxygen in Zn In_2S_4 was proved by XPS. HRTEM proved that the sheet oxygen doped Zn In_2S_4 was successfully loaded on the surface of layered g-C_3N_4. When the loading of g-C_3N_4 is 20, the composite exhibits the best degradation rate of Rhodamine B. The degradation rate of Rhodamine B by 20g-C _ 3N _ 3N _ 3N _ 2O _ 4 / O _ doped Zn In_2S_4 was 97% under 20 min visible light, which showed that the degradation effect of Rhodamine B was excellent, and the degradation effect was not obviously decreased after four cycles, which reflected the good stability of photocatalyst.
【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

【参考文献】