稀土改性Bi2WO6的制备及其光催化降解邻苯二甲酸酯的机理研究

Characters)：Phthalic acid esters (PAEs) are one kind of typical endocrine disruptors, which are widely used as plasticizers. Some PAEs have been detected in various environmental waters, such as surface waters, freshwaters, mineral waters, seawaters and urban lakes, which result in physiological and biochemical effects on organisms and human. Nowdays, PAEs have been paid attentions in the world. Some PAEs, such as dimethyl phthalate (DMP), di-n-butyl phthalate (DBP), diethyl phthalate (DEP), di-octyl phthalate (DOP) and di-(2-ethylhexyl) phthalate (DEHP), have been listed as priority pollutants by the U.S. Environmental Protection Agency, European Union and China National Environmental Monitoring Centre. It’s meaningful to study the degradation of PAEs in water, the removal pathway of PAEs, and the analysis of byproducts during the degradation process of PAEs. This project intends to the photocatalytic degradation of typical PAEs under simulated solar irradiation by photocatalytic oxidation technology. The main contents of this project includ (1) preparation of rare earth-modified bismuth tungstate oxides (RE/Bi2WO6) according to that rare earth elements with incomplete 4f and 5d orbitals, easy to produce multi-electron configuration, polymorphs, good thermal stability. The doping of appropriate amount of rare earth ions could change the the distribution of charge density in catalyst, the formation of defects, or the lattice type, which would affect the movement of photogenerated electron-hole pairs, adjust the distribution state, or change its energy band structure, and ultimately the photocatalytic properties would be modified; (2) the effects of different rare earth elements, doping amount, temperature of hydrothermal reaction, reaction time and pH of the reaction solution on the photocatalytic activity of RE/Bi2WO6; (3) the effects of different factors on the removal efficicency of PAEs, such as the amount of the photocatalyst, the initial concentration of PAEs, the pH value of reaction solultion, organic matters and inorganic co-ions in the solution; (4) the analysis of intermediates produced during the photocatalytic degradation process and the degradation pathway of PAEs under simulated solar irradiation as well as the degradation mechanism of RE/Bi2WO6. This project will provide a method for the removal of PAEs in water, and be contributed to elucidate the mineralization way of typical PAEs as well as develop the application of visible light photocatalytic oxidiation technology in the environmental pollution treatment.

塑化剂中使用最普遍的邻苯二甲酸酯(PAEs)是一类典型的环境内分泌干扰物，被认定为“第二个全球性PCB 污染物”，在多个国家和地区被列为“优先控制污染物”。PAEs在水环境中的溶出和蓄积已严重威胁到水生生物及人类的安全和健康，因而水体中 PAEs的去除是一个亟待深入研究的课题。本项目将采用光催化氧化技术在模拟太阳光的条件下降解典型的PAEs，主要研究：(1)利用稀土元素具有不完全的4f和5d电子填充轨道而产生的性能制备稀土改性Bi2WO6(RE/Bi2WO6)催化剂以调变Bi2WO6的可见光光催化活性；(2)通过多种表征手段和制备条件的设计考察不同电子填充轨道的稀土元素对Bi2WO6光催化活性的影响；(3) 考察在降解过程中催化剂投加量、PAEs初始浓度、反应时间、添加剂等因素对PAEs 去除的影响；(4)分析RE/Bi2WO6的活性机理以及PAEs的降解历程。

邻苯二甲酸酯（PAEs）作为“第二个全球性PCB 污染物”，其在多个国家和地区被列为“优先控制污染物”。赣南地区稀土资源丰富，而稀土元素具有不完全的4f轨道和5d轨道，具有易产生多电子组态、多晶型、热稳定性好等优点。结合稀土元素的优异性能开展稀土改性光催化剂的制备及降解邻苯二甲酸酯的研究。本课题利用La，Ce，Gd和Yb四种代表不同电子轨道填充状态的稀土元素进行Bi2WO6及TiO2的掺杂改性，通过X射线衍射(XRD)、扫描电镜/透射电镜(SEM/TEM)、X射线光电子能谱(XPS)、紫外-可见漫反射(UV-vis DRS)、N2吸附等手段对合成材料进行表征分析，发现稀土元素的掺杂可以有效提高光催化材料的比表面积、降低带隙能、拓展其可见光吸收范围；研究了典型PAEs物质邻苯二甲酸二甲酯（DMP）、邻苯二甲酸二乙酯（DEP）、邻苯二甲酸二丁酯（DBP）在UV、UV/TiO2、模拟太阳光/Bi2WO6体系中的降解；通过气相色谱-质谱联用法分析了DMP、DEP、DBP在不同体系中的降解产物，阐明了光解及光催化降解体系对邻苯二甲酸酯的不同降解机制；基于密度泛函理论，通过Materials Studio软件中的Castep模块对稀土掺杂TiO2的能带结构及态密度进行计算，发现了稀土掺杂后，材料晶格体积增大，带隙能降低，与实验结果基本一致，进一步印证了稀土元素能够改变催化剂的能带结构，并最终调变其光催化性能。本项目的研究为稀土元素在光催化剂的应用提供理论基础，同时为光催化氧化技术在有机废水中的处理提供基础研究。