AgBr复合光催化剂的合成、表征及去除水中典型污染物的应用研究

发布时间：2018-01-22 04:32

本文关键词： 光催化分子筛溴化银磷钨酸铯 AR18 Cr(Ⅵ) 苯酚　出处：《西北大学》2017年硕士论文　论文类型：学位论文

【摘要】：环境的日益恶化已成为人们的担忧,工业废水已经严重影响了人类的生存与发展,太阳能充足又清洁,已是人类所使用的一种重要的新能源,于是用光能,特别是太阳能并借助光催化剂克服环境污染问题是一种经济而又有效的新技术,而光催化技术的核心之一就是光催化的研究和开发。本论文以变价金属Cr掺杂MCM41分子筛为载体,通过负载TiO2和AgBr,通过AgBr修饰杂多酸磷钨酸铯,设计合成了 AgBr/TiO2/Cr-MCM-41和AgBr-CsxH3-xPW12O40(x=2.5)复合光催化剂。以AR18,六价铬离子和苯酚为催化底物,评价合成的光催化剂的活性,优化光催化去除水中有机、无机污染的反应条件;研究复合光催化剂的稳定性、光响应范围以及光催化降解水中典型污染物的机理,揭示高效、稳定光催化反应结构和性能关系,主要内容和研究结果如下:(1)使用水热法合成金属铬掺杂的MCM41,通过钛酸丁酯的水解在Cr-MCM41表面负载Ti02,得到Ti02-Cr-MCM41,最后用沉淀沉积法在催化剂的载体表面成功负载AgBr,得到AgBr-TiO2-Cr-MCM41多元复合光催化剂。使用多种表征方法对催化剂进行了分析,XRD和BET表明多元复合掺杂的催化剂良好的保持了分子筛的中孔结构,UV-Vis表明,所得催化剂有了较载体范围更宽的光吸收范围。通过可见光(λ400nm)照射下降解偶氮染料酸性大红AR181评价AgBr-Ti02-Cr-MCM41催化活性,探寻了最佳降解条件(pH=3.0,催化剂用量为5g/L)。通过一系列自由基抑制实验,发现·O2-是AgBr-Ti02-Cr-MCM41可见光照射下催化降解AR18的主要活性物质。另外通过循环实验和研究表明所得材料是能够重复使用的,每次使用时30 min后催化降解率都达到90%以上,并且使用次数越多,催化效率有增大的趋势,这是由于所得催化剂中存在变价金属Cr,六价铬充当电子受体,反应过程中被还原为三价铬,但当使用后的催化剂经过鼓风加高温煅烧之后,三价铬又被氧化为六价铬,接收电子的能力恢复。(2)通过简单的沉淀沉积法,以杂多酸盐为载体和电子梭,通过AgBr复合构筑了AgBr-Cs2.5H0.5PW12O40 异质结复合光催化剂。通过 XRD,BET,SEM,XPS,UV-vis 等多种表征方法对所得材料进行了表征,将有机染料酸性大红AR18作为催化底物,探讨了关系催化剂催化性质的几种重要因素,如溶液初始酸碱度,反应体系中催化剂的使用量,催化底物的初始浓度等。又通过在催化反应过程中加入活性物质抑制剂,探讨了催化反应中的活性物质。5次循环实验后催化剂的催化活性仍然很高,说明构建的复合催化剂具有较高的稳定性。(3)利用催化剂AgBr-Cs2.5H0.5PW12O40尝试同时光催化降解水中无机污染物Cr(VI)和有机污染物苯酚,研究两者协同降解情况。讨论了分别改变Cr(VI)和苯酚的量和溶液初始pH值对两者催化降解的影响,结果表明,初始反应液为酸性时Cr(VI)的降解速率较快,为碱性时苯酚降解速率较快。
[Abstract]:Environmental deterioration has become a concern for people, industrial wastewater has seriously affected the survival and development of human beings, solar energy is sufficient and clean, has been used as an important new energy, so use light energy. Especially solar energy and photocatalyst to overcome environmental pollution is an economical and effective new technology. One of the core of photocatalytic technology is the research and development of photocatalysis. In this thesis, the carrier of variable-value metal Cr doped MCM41 molecular sieve is used as the carrier, which is supported by TiO2 and AgBr. Caesium phosphotungstate was modified by AgBr. The composite photocatalysts of AgBr/TiO2/Cr-MCM-41 and AgBr-CsxH3-xPW12O40O40xA2.5) were designed and synthesized by AR18. Hexavalent chromium ion and phenol were used as the catalytic substrates to evaluate the activity of the synthesized photocatalyst and to optimize the reaction conditions of photocatalytic removal of organic and inorganic pollution in water. The stability, the range of photoresponse and the mechanism of photocatalytic degradation of typical pollutants in water were studied, and the relationship between the structure and performance of high efficient and stable photocatalytic reaction was revealed. The main contents and results are as follows: (1) Metallic chromium doped MCM41was synthesized by hydrothermal method, and Ti02 was loaded on the surface of Cr-MCM41 by hydrolysis of butyl titanate. Ti02-Cr-MCM41 was obtained and AgBr was successfully supported on the surface of the catalyst by precipitation deposition method. AgBr-TiO2-Cr-MCM41 multicomponent composite photocatalyst was obtained and the catalyst was analyzed by various characterization methods. The results of XRD and BET showed that the multi-doped catalyst kept the mesoporous structure of molecular sieve well and UV-Vis showed. The resulting catalyst has a wider range of light absorption than the carrier. Through visible light (位 400nm). Degradation of azo dye acid scarlet AR181 under irradiation to evaluate the catalytic activity of AgBr-Ti02-Cr-MCM41. The optimum degradation conditions (pH = 3.0, catalyst dosage = 5 g / L ~ (-1)) were investigated, and a series of free radical inhibition experiments were carried out. It was found that O _ 2- was the main active substance for the catalytic degradation of AR18 under visible light irradiation by AgBr-Ti02-Cr-MCM41. In addition, the cycling experiments and studies showed that the obtained material was able to repeat the degradation of AR18. Yes. The catalytic degradation rate reached more than 90% after 30 min, and the higher the use times, the higher the catalytic efficiency, which was due to the existence of the metal Cr in the catalyst. Hexavalent chromium acts as an electron receptor and is reduced to trivalent chromium during the reaction, but after the catalyst is calcined by blast and high temperature, trivalent chromium is oxidized to hexavalent chromium. The recovery of the ability to receive electrons. 2) by a simple precipitation deposition method, using heteropolyacid as the carrier and electron shuttles. AgBr-Cs2.5H0.5PW12O40 heterojunction photocatalyst was synthesized by AgBr. The organic dye acid reddish AR18 was used as the catalyst substrate, and several important factors related to the catalytic properties of the catalyst were discussed. For example, the initial pH of the solution, the amount of catalyst used in the reaction system, the initial concentration of the catalyst substrate, etc. The catalytic activity of the catalyst is still very high after the experiment of the active substance in the catalytic reaction. The results show that the composite catalyst has high stability. The catalyst AgBr-Cs2.5H0.5PW12O40 is used to try to photocatalyze the degradation of inorganic pollutants in water at the same time. And organic pollutants, phenol. The effects of the amount of CrVI and phenol and the initial pH value of the solution on the catalytic degradation were discussed. The degradation rate of CrVI was faster when the initial reaction solution was acidic, and the degradation rate of phenol was higher when the reaction solution was alkaline.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;X52

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