Bi系列可见光催化剂的制备及其催化降解性能研究

发布时间：2018-05-31 18:11

本文选题：BixOyIz + 亚甲基蓝　；参考：《郑州大学》2015年硕士论文

【摘要】：现代化生产过程中排放的有机染料和除草剂是水体中主要污染物,这些污染物对环境和生物都会产生严重的危害,因此对水体中这些污染物的去除越来越重要,绿色的光催化技术因为其降解效率高和对环境友好等优点成为一种治理环境污染的研究热点。本文利用水热法和油浴法制备具有不同晶体形貌的BixOyIz催化剂,使用水热法合成了球状的Bi OI和花瓣状的Bi4O5I2,使用油浴法合成了层状纳米结构的Bi7O9I3。利用紫外-可见光漫反射(UV-vis)、扫描电镜(SEM)、X射线衍射(XRD)、比表面积分析(BET)和X射线光电子能谱(XPS)对催化剂进行表征分析。结果如下:1.通过XRD和SEM表征分析知道三种催化剂Bi OI、Bi4O5I2和Bi7O9I3没有很多杂质峰,纯度比较高结构,分别为球状、花瓣球状和分层纳米结构;2.通过UV-Vis表征分析可知Bi OI、Bi4O5I2和Bi7O9I3在可见光区均有很好的吸收,最大吸收波长分别为673nm、640nm和630nm,禁带宽度分别1.84e V、1.93e V和1.97e V;3.通过BET表征分析得到比表面积分别是:18、12和8m2/g。4.利用XPS对Bi4O5I2进行表征分析可知,三种元素摩尔比为3.7:5.2:1.6,再通过数据分析得出三种元素的化合价为+3,-2,-1,可以确定这种物质就是Bi4O5I2。在光催化降解开始前首先做了催化剂的暗吸附实验,并利用Freundlich和Langmuir等温吸附模型模拟了暗吸附过程,结果是Bi OI对MB的吸附更符合Freundlich模型,而且高温不利于吸附反应。在模拟可见光灯照射条件下,测定了Bi OI对染料亚甲基蓝的降解实验,Bi4O5I2和Bi7O9I3对除草剂2,4-D的降解实验,考察了催化剂浓度、污染物的初始浓度、光照时间等条件对降解的影响,同时做了降解动力学分析,并在最佳的条件下进行了降解实验,结果如下:(1)在MB的浓度为50mg/L,催化剂的浓度为1g/L的条件下,Bi OI对MB的降解率达到98%,降解动力学符合准二级模型;(2)在催化剂浓度为1g/L时,2,4-D初始浓度为50mg/L Bi4O5I2对的降解率达到84%左右,降解动力学符合准二级模型;(3)在相同的操作条件下Bi7O9I3对2,4-D的降解率达到95%左右。在夏季晴天和阴天自然光照射下,分别使用Bi OI、Bi4O5I2和Bi7O9I3作为催化剂进行对2,4-D的降解研究;还考察了Bi7O9I3在春、夏、秋、冬四季光照射下催化降解效果实验,降解效率分别为85.23%、98.66%、87.25%和82.75%;为了考察不同单色光对降解的影响,我们利用单色光片分离出6种太阳光单色光,分别是:红、橙、黄、绿、蓝和紫光,测定其光强度,并在单色光照射下做了催化剂Bi7O9I3对2,4-D的降解实验,6种单色光的降解效率相差不大,其中紫光降解率最高,达到90.23%。研究结果表明合成的Bi OI、Bi4O5I2和Bi7O9I3催化剂具有很好的结构形貌和可见光吸收,可以很好的降解水中污染物,具有很好的实际应用前景。
[Abstract]:Organic dyes and herbicides discharged in modern production process are the main pollutants in water, which will cause serious harm to the environment and organisms. Therefore, the removal of these pollutants in water is becoming more and more important. Green photocatalytic technology has become a research hotspot in environmental pollution control because of its high degradation efficiency and environmental friendliness. In this paper, BixOyIz catalysts with different crystal morphologies were prepared by hydrothermal method and oil bath method. The spherical BiOI and petal-like Bi4O5I2 were synthesized by hydrothermal method, and the layered Bi7O9I3 was synthesized by oil bath method. The catalysts were characterized by UV-vis-vis, SEM, BET and XPSs. The catalysts were characterized by X-ray diffraction (XRD), specific surface area analysis (BET) and X-ray photoelectron spectroscopy (XPS). The result is as follows: 1. The results of XRD and SEM analysis showed that there were no impurity peaks in the three catalysts BiOI _ 4O _ 5i _ 2 and Bi7O9I3, and their purity was relatively high, which were spherical, petal-shaped and layered nanostructures respectively. The UV-Vis analysis shows that BiOI Bi4O5I2 and Bi7O9I3 have good absorption in visible region, the maximum absorption wavelengths are 673 nm and 630 nm, respectively, and the bandgap is 1.84 e V ~ (1 93e) V and 1.97 e V ~ (3). By BET characterization, the specific surface areas are: 1: 18 12 and 8 m2 / g. 4, respectively. Bi4O5I2 was characterized by XPS, and the molar ratio of three elements was 3.7: 5.2: 1.6. Through the data analysis, the combined valence of the three elements was found to be 3 ~ 4O _ 5i _ 2i ~ (-1), which can be confirmed as Bi4O _ 5i _ 2i _ 2. Dark adsorption experiments were done before photocatalytic degradation, and the dark adsorption process was simulated by Freundlich and Langmuir isothermal adsorption models. The results showed that BiOI adsorption of MB was more in line with the Freundlich model, and the high temperature was not conducive to the adsorption reaction. The degradation experiments of Bi4O5I2 and Bi7O9I3 on herbicide 24-D were carried out under simulated visible light irradiation. The effects of catalyst concentration, initial concentration of pollutants and illumination time on the degradation were investigated. At the same time, the degradation kinetics was analyzed, and the degradation experiment was carried out under the best conditions. The results were as follows: at the concentration of MB 50 mg / L and the concentration of 1g/L as catalyst, the degradation rate of MB was 98%, and the degradation kinetics was in accordance with the quasi second order model, and the degradation rate was about 84% at the initial concentration of 50mg/L Bi4O5I2 when the concentration of the catalyst was 1g/L, and the degradation rate of BiOI was about 84% when the concentration of the catalyst was 50 mg 路L ~ (-1), and the degradation rate of BiOI was about 84%. The degradation rate of 24-D by Bi7O9I3 was about 95% under the same operating conditions. BiOI Bi4O5I2 and Bi7O9I3 were used as catalysts to study the degradation of 2-D on sunny and overcast days in summer, and the catalytic degradation effect of Bi7O9I3 under light irradiation in spring, summer, autumn and winter was also investigated. The degradation efficiency was 85.230.66% and 82.75%, respectively. In order to investigate the effect of different monochromatic light on the degradation, we separated six kinds of monochromatic solar light with monochromatic light, namely red, orange, yellow, green, blue and purple, and measured their light intensity. The degradation efficiency of 6 monochromatic light was not different from that of Bi7O9I3 catalyst under monochromatic light irradiation, and the degradation rate of purple light was the highest (90.2335). The results show that the synthesized BiOI-Bi4O5I2 and Bi7O9I3 catalysts have good structure morphology and visible light absorption, and can degrade pollutants in water well, and have a good prospect of practical application.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;X52

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