【作者】 艾智慧；

【导师】 陆晓华；

【作者基本信息】 华中科技大学 ， 环境工程， 2004， 博士

【摘要】 TiO2多相光催化氧化(PCO)是近二十年来迅速发展并且广泛研究应用的水处理技术。但是,TiO2光催化技术的实际应用还存在着诸如量子效率低,对太阳能的利用有限等技术难题。利用微波(MW)与紫外光(UV)的耦合、超声(US)与UV的耦合来提高光催化过程中的量子效率,以及利用改性TiO2催化剂来提高光催化过程中的量子效率,成为目前PCO领域关键性研究内容之一。本文首先介绍了近年来PCO技术以及MW技术、US技术降解水中有机污染物的研究进展和氯酚类(CPs)污染物的处理技术现状。以难降解有机物污染物CPs为处理对象,系统地研究微波辅助光催化氧化(MW/PCO)和超声辅助光催化氧化(US/PCO)这两种能量耦合水处理技术降解水溶液中CPs的工艺条件以及影响因素,探讨了MW、UV耦合,US、UV耦合提高光催化量子效率的作用机理。同时制备了碳材料改性的TiO2催化剂(C-TiO2)——石墨改性TiO2催化剂(G-TiO2)、活性炭改性TiO2催化剂(AC-TiO2)、碳纳米管改性TiO2催化剂(CNTs-TiO2),研究了C-TiO2的光催化活性。试验表明MW/PCO、US/PCO可望成为水污染治理的新途径,CNTs-TiO2、AC-TiO2催化剂为提高光催化量子效率提供了可能。微波辅助氧化技术降解4CP的研究主要结论如下:①30mg/L的4CP溶液的微波直接光降解(MW/UV)、微波辅助光催化降解(MW/UV/P25)服从一级反应动力学方程。MW/UV/P25体系中,碱性条件、通入氧气、提高光照度以及外加H2O2均能提高4CP的降解率,P25的用量在1g/L时4CP的降解率最高。在MW/UV体系中,酸性或碱性条件、向体系中通入氧气、提高光照度、加入H2O2能提高4CP的降解率。②30mg/L的4CP溶液在不同氧化体系中的降解率从大到小排序为:MW/UV/P25/H2O2> MW/UV/P25> MW/UV/H2O2> MW/UV> UV/P25/H2O2> UV/H2O2> UV/P25> UV> MW/H2O2> H2O2。MW与P25、UV、H2O2有协同效应。2. 微波辅助光降解氯酚类污染物的研究主要结论如下:①溶液中0.1mM的4CP,2-氯酚(2CP),4-氯-3-甲基酚(4C3MP),2,4-二氯酚(2,4-DCP),2,4,6-三氯酚(2,4,6-TCP),五氯酚(PCP)的微波辅助光解均服从一级反应<WP=5>动力学方程;CPs在 MW/UV体系中的降解速率常数从大到小排列顺序为:2CP > 4C3MP > 2,4-DCP =4CP > 2,4,6-TCP > PCP ;在 MW/UV/P25体系中的降解速率常数从大到小排列顺序为:4C3MP > 2,4-DCP > 2CP > 4CP > 2,4,6-TCP > PCP。单氯酚比多取代氯酚更加容易光解。②微波辅助光催化降解4CP的主要中间产物为苯酚、氯苯、对苯醌、对苯二酚等,降解PCP的主要中间产物为2,3,5,6-四氯对苯醌、2,3,4,6-四氯对苯二酚、四氯酚。CPs降解的机理是紫外光解和羟基自由基(?OH)亲电子加成脱氯过程。③运用PM3算法计算得到的分子结构参数结合光解速率进行PLS分析,得到了CPs光降解速率与量子化参数之间的关系模型,模型的Q2cum分别为0.8776和0.9545 (>0.5)。参数Ehomo、Elumo+Ehomo、Elumo、N 、Mw、Elumo-Ehomo、 (Elumo-Ehomo)2是决定CPs光解速率的主要因素;CPs的光解速率随着Ehomo、Elumo+Ehomo、Elumo、Elumo-Ehomo、 (Elumo-Ehomo)2的增大而增大,随着N 、Mw的增大而减小。3. 碳材料改性TiO2催化剂(C-TiO2)的制备及性能研究主要结论如下:①CNTs、AC、G对80mg/L的PCP溶液的饱和吸附量分别为162.4mg/g、126.6mg/g、8.0mg/g,CNTs对PCP具有优异的吸附性。②用Sol-Gel法制备锐钛矿型纳米TiO2催化剂,以及G-TiO2 、AC-TiO2、CNTs-TiO2催化剂。AC的掺杂量5.81%时,AC-TiO2光催化活性最大,再增加AC掺杂量,催化活性下降;CNTs的掺杂量6.7%时,CNTs-TiO2光催化活性最大,掺杂量超过该比例,催化活性下降;G-TiO2催化剂的催化活性比TiO2的活性低。③CNTs对微波有着较高的吸收性能,在PCP的降解过程中CNTs对微波的吸收导致CNTs-TiO2表面产生更多的“热点”,微波对于CNTs-TiO2协同作用大于对TiO2的协同作用。4. 超声辅助光催化降解CPs的研究主要结论如下:①US/UV/P25降解PCP时,超声功率的提高促进了PCP降解;溶液pH值对降解速率影响显著,低pH值有利于降解;低浓度的H2O2促进了PCP的降解,而高浓度H2O2促进效果不明显;Fe3+的添加促进了PCP的降解,而正丁醇显示了一定的抑制作用。在不同的气氛条件下的降解率从高到低顺序均服从O2>Air>N2。②超声光催化降解PCP具有良好的效果,光催化与超声波降解之间存在光声协同作用。PCP的降解在US、UV/P25、US/UV/P25三个体系中的降解均符合一级反应动<WP=6>力学模式。③在US体系中,不同CPs的降解率从大到小依次为4CP> 4C3MP> 2CP> 2,4,6-TCP> 2,4-DCP> PCP;在US/UV/P25体系中,不同CPs的降解率从大到小依次为4C3MP=2CP> 2,4-DCP> 4CP> 2,4,6-TCP> PCP。PCP的降解速率最慢,其次是2,4,6-TCP或2,4-DCP,单氯酚如2CP、4C3MP和4CP易降解。更多还原

【Abstract】 TiO2 heterogeneous photocatalytic oxidation(PCO) has been successfully used in wastewater treatment and continues to be an active field of application and research since 1980’s. However, there are some drawbacks, such as the low photocatalytic quantum efficiency, only more or less 4% sunlight can be used, and so on, which hamper successful application of PCO on industrial scale operation for wastewater treatment. Thus, research on improving the photocatalytic efficiency by coupling microwave technology(MW) 、ultraviolet technology(UV)、ultrasound technology(US) or preparation modified nano-TiO2 catalysts is becoming one of the key research contents in PCO field nowadays.In this dissertation the recent research on the degradation of organic pollutants by PCO, MW and US technology and hybrid technologies for the treatment of chlorophenols(CPs) were reviewed at first. Then the research on the microwave assisted UV degradation (MW/UV), microwave assisted UV TiO2 photocatalytic degradation (MW/UV/P25), ultrasound assisted UV TiO2 photocatalytic degradation (US/UV/P25) were used to degrade CPs respectively. The factors which influenced on the efficiency and mechanism of degradation were investigated. Meanwhile, carbon materials (graphite, actived carbon powder, carbon nanometer tube) modified nano-TiO2 catalysts were prepared by sol-gel method and their activity were also studied. The experimentation showed that not only both MW/PCO and US/PCO technolygies might provide a potential method for industrial wastewater treatment, but also CNTs-TiO2 、AC-TiO2 catalysts might make it possible to improve the PCO quantum efficiency.1. Results of microwave assisted oxidation degradation of 4CP are summarized as follows:① The pseudo-first-order degradation kinetics of 4CP were observed for both MW/UV and MW/UV/P25. In MW/UV/P25 system, degradation rate increases with dosage of TiO2, but overdoses may cause rate retardation, degradation was slightly enhanced in acid or alkaline solutions, reaction can be enhanced while increasing the irradiation intensity, purging oxygen or adding H2O2 to the dispersions. In MW/UV system, the degradation was enhanced in alkaline solution, the reaction can be enhanced while <WP=8>increasing the irradiation intensity, purging oxygen or adding H2O2 to the solution.②The sequence of the degradation rate of 4CP in different system is MW/UV/P25/H2O2> MW/UV/P25> MW/UV/H2O2> MW/UV> UV/P25/H2O2> UV/H2O2 >UV/P25 > UV > MW/H2O2> H2O2. The degradation was enhanced with the MW because of signicicant synergistic effects between MW and UV、TiO2、H2O2.2. Results of microwave assisted photo-degradation of CPs are summerized as follows: ① Six kinds of selected CPs as 2CP, 4CP, 4C3MP, 2,4-DCP, 2,4,6-TCP, PCP were degradation in MW/UV or MW/UV/P25 system respectively. The degradation of CPs in MW/UV/P25 is more efficient than that in the MW/UV one as more free radicals(?OH) generated with the present of TiO2 conditions. The degradation is faster for monohalogenated phenols than poly-substituted phenols with an exception of 4CP and the reaction rate of degradation in is 2CP > 4C3MP > 2,4-DCP =4CP > 2,4,6-TCP > PCP the presence of MW/UV and is 4C3MP > 2,4-DCP > 2CP > 4CP > 2,4,6-TCP > PCP in MW/UV/P25. ② The degradation of 4CP in MW/UV/P25 system appears to go through the mechanism which generating intermediates as phenol,chlorobenzene,hydroquinone and benzoquinone. The main intermediates are TTCP, tetrachloro-hydroquinone and tetrachloro-benzoquinone when PCP was degraded in MW/UV/P25 method. The mechanism for the degradation of CPs involves both radical reactions and direct photolysis.③ By the use of partial least squares(PLS) method, two models for the degradation rate constants of 6 kinds of CPs were successfully developed while reacting in the the MW/UV/P25 system and MW/UV system, Q2cum of the two models are 0.8776 and 0.9545 respectively(>0.5). The PM3 results show that it is mainly the Ehomo、Elumo+Ehomo、Elumo、N 、Mw、Elumo-Ehomo、 (Elumo-Ehomo)2 that determine the degradation rate constan更多还原