类石墨烯氮化碳光催化降解有机污染物的性能研究

 2022-06-07 09:06

论文总字数:31180字

摘 要

氮化碳是近年来新兴半导体光催化剂材料,在光解水、环保等领域有巨大应用前景。石墨相氮化碳纳米片(g-C3N4)以其恰当的带隙和优良的微观结构有着更好的光催化性能。氮化碳的合成需要氮源、碳源和其他金属或非金属掺杂元素混合得到的前驱体,g-C3N4合成过程一般策略为高温烧结前驱体使之聚合形成体相氮化碳,而后进行剥离得到g-C3N4,本实验中采用高能微波法直接合成表面光滑的g-C3N4。本实验合成g-C3N4的紫外-可见光谱在407nm处有位于可见光区的吸收边,对应带隙约为3.0eV。而后利用罗丹明B和亚甲基蓝作为模拟污染物进行g-C3N4的光催化降解实验,通过可见光(λ>420nm)照射加入g-C3N4的有机污染物模拟溶液进行光催化能力的评估,g-C3N4可在60min内使罗丹明B或亚甲基蓝的脱色率超过90%,光催化能力远远优于体相石墨相氮化碳。通过对比在g-C3N4光催化液相中加入羟基自由基捕捉剂叔丁醇或空穴捕捉剂三乙醇胺降解过程中的动力学差异,可研究是何种活性粒子在光催化过程中起主要作用。结论表明,羟基自由基在光催化过程中破坏罗丹明B侧链发色基团,进而导致液相颜色消失。

关键词:g-C3N4,高能微波法,光催化,光催化机理

Abstract

Carbon nitride is an emerging semiconductor photocatalyst material in recent years. It has great application prospects in the fields of photolysis of water and environmental protection. Graphite phase carbon nitride nanosheets (g-C3N4) have better photocatalytic properties with their proper bandgap and fine microstructure. The synthesis of carbon nitride requires a precursor obtained by mixing a nitrogen source, a carbon source, and other metal or non-metal doping elements. The general strategy for the synthesis of g-C3N4 is to sinter the precursor at a high temperature to polymerize to form a bulk phase carbon nitride, and then proceed. g-C3N4 was obtained by stripping. In this experiment, high-energy microwave method was used to directly synthesize g-C3N4 with smooth surface. In this experiment, the UV-Vis spectrum of the synthesized g-C3N4 has an absorption edge in the visible region at 407 nm, and the corresponding band gap is about 3.0 eV. Then, the photocatalytic degradation experiment of g-C3N4 was performed using Rhodamine B and methylene blue as simulated pollutants. The photocatalytic ability of g-C3N4 organic contaminants was evaluated by irradiation with visible light (λgt;420 nm), and g-C3N4 can be evaluated. The decolorization rate of Rhodamine B or methylene blue is more than 90% in 60 minutes, and the photocatalytic ability is far superior to that of bulk graphite phase carbon nitride. By comparing the kinetic difference in the degradation process of tert-butanol, a hydroxyl radical scavenger, or triethanolamine, a hole trapping agent, in the photocatalytic liquid phase of g-C3N4, it can be studied which active particle plays a major role in the photocatalytic process. . The results show that hydroxyl radicals destroy the chromophoric groups of Rhodamine B side chain during photocatalysis, which leads to the disappearance of liquid phase color.

KEY WORDS:g-C3N4, high-energy microwave method, photocatalysis, photocatalysis mechanism

目录

摘要……………………………………………………………………………………II

Abstract………………………………………………………………………………III

  1. 绪论……………………………………………………………………………2
    1. g-C3N4制备策略与改性…………………………………………………6
    2. g-C3N4表征与结构………………………………………………………8
    3. g-C3N4的电子结构………………………………………………………9
    4. g-C3N4在光催化领域应用………………………………………………9
  2. 石墨相氮化碳的合成…………………………………………………………11

2.1合成过程基本原理……………………………………………………………11

2.2微波烧结合成…………………………………………………………………11

2.3本章小结………………………………………………………………………11

  1. 石墨相氮化碳的表征…………………………………………………………13

3.1石墨相氮化碳表征的方法指导………………………………………………13

3.2 X射线衍射表征………………………………………………………………13

3.3傅里叶红外光谱表征…………………………………………………………14

3.4荧光光谱表征…………………………………………………………………15

3.5紫外-可见光漫反射表征………………………………………………………16

3.6 SEM表征………………………………………………………………………17

3.7本章小结………………………………………………………………………17

  1. 石墨相氮化碳光催化性能与机理……………………………………………18

4.1光催化过程概述与研究方法…………………………………………………18

4.2罗丹明B的降解过程…………………………………………………………18

4.3亚甲基蓝的降解过程…………………………………………………………24

4.4降解过程活性粒子与反应过程………………………………………………27

4.5本章小结………………………………………………………………………29

  1. 结论与展望……………………………………………………………………30

5.1结论……………………………………………………………………………30

5.2展望……………………………………………………………………………30

致谢………………………………………………………………………………………31

参考文献…………………………………………………………………………………32

  1. 绪论

人类发展进入现代社会后,能源需求呈几何倍数激增,合成化学品使用需求也日益增长。上世纪战后,党和人民迫切地盼望从一穷二白的废墟之上建立起独立自主的新中国,这离不开能源的消耗;改革开放以来国内以制造业为根基的经济基础带动上层建筑飞速发展,这一阶段离不开合理规划能源使用的策略;进入新世纪,人们愈发地感受到环境问题带来的困扰,如何平衡国力增长和环境保护自然地成为全国人们需要面对的问题;中国共产党第十九次全国代表大会(下述“十九大”)指出,我国主要矛盾已悄然转变为“人民日益增长的美好生活需要和不平衡不充分的发展之间的矛盾”[1],矛盾当中也包括经济发展与环境保护之间的不平衡。今年是中华人民共和国国民经济和社会发展第十三个五年规划纲要(下述“十三五”)执行的关键一年,“十三五”是否能取得预期成果取决于全党与全国人民的决策与努力。发展生态文明建设和环保式生产是“十三五”计划中对环境提出的新要求,绿色制造防治水与空气污染,两部委关于印发《水污染防治重点行业清洁生产技术推行方案》的通知,造纸、焦化、氮肥、有色金属、印染、农业、副食品、原料药、制革、农药、电镀、制糖在内的11项产业列为重点水与空气污染查缉对象,造纸业列为榜首,因为全国水污染物的12%来自造纸,还远高于传统民众观感中的重工业和石化[2]

水污染是我国经济发展至今必须面临的巨大挑战,水质污染会影响整个生态系统,包括水体内的所有动植物。这类的影响不只是针对个别物种或是特别地区的一些生物,而会对整个自然界造成影响。水体污染物种类繁杂,毒理学机制不尽相同。在实验室中同行们广泛选用罗丹明B、甲基橙、亚甲基蓝等芳环共轭或偶氮共轭型有机染料作为模拟污染物,通过吸收光强改变衡量模拟有机污染物在水中降解程度。

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