【作者】 李嘉庆；

【导师】 金利通；

【作者基本信息】 华东师范大学 ， 分析化学， 2007， 博士

【摘要】 1972年Fujishima和Honda在Nature杂志上发表了TiO2电极光催化分解水的科研成果,这一成果具有非常重要的意义,它不仅仅揭示了利用TiO2可以把光能转化为化学能,同时更标志着光催化新时代的开始。来自化学、物理、材料等领域的学者围绕太阳能的转化和储存,探索多相光催化过程的原理,致力于提高太阳能的转化效率,并拓展其应用领域。TiO2光催化性能的应用已经渗透到材料、能源、环保等多个领域,成为当今科学研究中的一大热点。在对TiO2光催化性能研究的基础上,人们对利用TiO2光催化技术进行环境治理产生了兴趣。从上世纪70年代初期以来,国外的许多学者竞相开展了这方面的研究。在众多环境污染治理技术中,TiO2光催化技术作为一种新型的高级氧化技术具有其独特的优势:以TiO2作为光催化剂的多相光催化反应能够在比较温和的条件下深度的进行;可以利用太阳能直接激活光催化剂,驱动氧化-还原反应。TiO2光催化技术在环境治理过程中的广泛应用引起了环保技术的全新革命,这一革命现已波及污水治理、水质监测、空气净化及保洁除菌等诸多领域。水质污染是环境污染的一大方面,污水能否达标排放由污水的污染指数决定,其中最重要的指标是污水的COD值。COD是指在一定条件下,水体中有机物或其他还原性物质被强氧化剂氧化所消耗的氧化剂所对应的氧的物质浓度(mg l-1)。测定过程中有机物或其他还原性物质的氧化程度决定了测定COD结果的准确程度。具有光催化活性的TiO2在光激发下,能产生具有强氧化性的活性氧自由基(如羟基自由基)等一类强氧化剂,可将水中的有机污染物深度矿化。利用此原理可望实现对有机污染物的快速、实时测定,为水体中有机污染物总量的测定提供一种全新的理念和思路。本论文制备并表征了一些具有光催化活性的TiO2薄膜,探讨了TiO2薄膜光催化剂的光催化氧化有机物的机理,提出了利用光催化氧化技术对水体化学需氧量进行测定的新方法,还以该方法为基础开发研制了新型的COD分析仪。本论文内容共分五章:第一章绪论本章内容对TiO2光催化剂的结构、性能及研究现状,TiO2薄膜的制备、TiO2薄膜光催化性能的优化及其应用等方面的进展作一综述。对当前国内外化学需氧量测定技术的现状及进展作了详细的阐述。第二章TiO2薄膜光催化氧化有机物的研究本章内容分为两节,分别以罗丹明B和亚甲基兰作为模拟物,进行了利用Ti/TiO2薄膜对水体中有机物光催化氧化的研究。第一节介绍了利用激光煅烧结合溶胶-凝胶的方法制备了Ti/TiO2电极,并利用X射线衍射仪(XRD)和原子力显微镜(AFM)对该电极进行了表征。进行了以该电极为工作电极,光催化降解罗丹明B的实验。在实验过程中,探讨了煅烧时所用的激光能量对该电极光催化性能的影响,以及阳极电压、pH值对光催化降解反应的影响,并且对该电极在不同条件下降解罗丹明B的过程进行了对比研究,最后还比较了激光煅烧和马弗炉烧结制得的Ti/TiO2电极光催化降解罗丹明B的过程,结果表明,电助光催化可以比单纯的光催化更有效氧化有机物,而且用激光煅烧结合溶胶-凝胶法制备的Ti/TiO2电极具有更好的光催化性能。第二节介绍了利用阳极氧化结合激光煅烧的方法制备了Ti/TiO2电极,对该电极进行了XRD表征,结果表明制得的薄膜中TiO2的晶型主要是锐钛矿型。同时还通过交流阻抗(EIS)法初步研究了Ti/TiO2电极的光催化性能,为了进一步研究制得的Ti/TiO2电极光催化性能,进行了光催化氧化亚甲基兰(MB)的实验。在实验过程中,探讨了利用Ti/TiO2电极电助光催化降解有机物的机理,以及不同条件对光催化反应的影响,为了研究对有机物深度矿化的情况,还考察了降解过程中反应液化学需氧量(COD)的去除率。结果表明,用阳极氧化-激光锻烧法制备的Ti/TiO2电极不仅具有更强的光催化氧化有机物的能力,还具有更高的对有机物的深度矿化的选择性。第三章石英管负载TiO2薄膜光催化氧化测定化学需氧量的应用研究本章制备并表征了石英管负载的TiO2薄膜,同时还提出了用石英管负载TiO2结合K2Cr2O7的体系光催化氧化检测水体化学需氧量的新方法,在这个体系中,K2Cr2O7极易捕获TiO2表面光生电子,提高TiO2光催化氧化能力。对于给定样品,可以根据K2Cr2O7光催化还原产物Cr(Ⅲ)吸光度值的变化,来定量计算样品的COD值。以葡萄糖为标准物质,探讨了该方法测定化学需氧量的最佳反应条件,并拟合了工作曲线(线性范围为50～500 mg l-1,最低检测限为20 mgl-1)。将该方法用于实际水样检测,分析时间短,减少了二次污染,光催化反应后水样无需后处理可直接进行测定,本方法与国家COD标准分析法具有好的相关性。第四章利用溶胶-凝胶结合激光煅烧法制备Ti/TiO2电极及其应用于测定化学需氧量的研究本章采用溶胶-凝胶结合激光煅烧的方法制备了Ti/TiO2电极,并用X射线衍射分析仪(XRD)和交流阻抗法(EIS)对其进行了表征,同时还将该电极作为安培传感器,应用于水体化学需氧量(COD)的测定。本方法是利用Ti/TiO2电极对水样中的有机物进行电助光催化氧化,在反应同时通过采集工作电极上产生的电流信号来对水体的COD值进行定量的。将该方法用于标准水样和实际水样测定,分析时间短,减少了对环境的二次污染,本方法与国家COD标准分析法进行比对具有好的相关性。另外,还将用激光煅烧制备的和马弗炉煅烧制备的Ti/TiO2电极进行了对比研究,结果表明,利用激光煅烧制备的传感器具有更好的光催化活性,用于水体COD值的测定也具有更高的检测灵敏度。第五章基于光-电协同催化技术的COD测定方法的建立及分析仪的研制本章介绍了一种利用光-电协同催化技术测定水体COD值的方法,并在此基础上开发和研制了用于水体COD值测定的流动注射分析仪。第一节制备了Ti/TiO2/PbO2电极,还用原子力显微镜(AFM)对该电极的表面形貌进行了表征,同时还利用电化学技术研究了该电极上发生的光-电协同催化作用,并同电催化、光催化作用进行了比较。在这些研究的基础上,还将该电极应用于水体化学需氧量(COD)的测定。利用光-电协同催化的方法,在20.0～2500.0 mg l-1的COD值范围内,该电极上产生的电流响应信号与水样中的CODCr值成正比例关系,本方法检出限为10.0 mg l-1(S/N=3)。将该方法用于实际水样测定,结果表明,利用光-电协同催化法能够提高水样中有机物在传感器上产生的电流响应信号,还具有更高的灵敏度。具有分析时间短,环境友好与标准法相关性好等优点。第二节介绍了根据光-电协同催化氧化的原理,以Ti/TiO2/PbO2电极作为安培传感器,并结合流动注射分析法,开发研制了以电流法为检测手段的化学需氧量流动注射分析仪。实验结果表明,在30～2000 mg l-1的COD值范围内,该安培传感器上产生的电流响应信号与水样中的CODcr值成正比例关系,本方法检出限为20 mg l-1(S/N=3),使用该仪器能够实现对污水COD值的连续测定,自动化程度高,还具有操作简单、耗时短,测定精密度高,准确性好和环境友好等优点。试用该仪器测定几种废水并将测定结果与国标法(CODCr)对照,相关系数(R)达到0.9912。更多还原

【Abstract】 On the basis of the study of photo-catalytic ability of TiO₂, people are very interested in its application in the environmental treatment. Since the early seventies of the last century, the research has been started in this field, and many methods have been used to treat environmental problems. Among them, the photo-catalysis of TiO₂ which functions as the advanced oxidation technique has many unique advantages. Firstly, heterogeneous photo-catalysis in which TiO₂ is the photo-catalyst can occur completely under relatively gentle conditions. Secondly, solar power can be used to stimulate photo-catalysis directly in order to make redox take place. The wide application of photo-catalysis of TiO₂ in the environmental treatment has led to a revolution which is being used in many aspects such as the water treatment, quality detection of water, air decontamination, sterilization, and etc.Water pollution is a significant aspect of environmental pollution. Whether the polluted water can be discarded or not depends on the index of pollution. The most important one is the value of COD （chemical oxygen demand） which is defined as the number of oxygen equivalents consumed in the oxidation of organic compounds by strong oxidizing agents(mg l^₁). The accuracy of COD measurement is determined by the extent of the oxidation of the organics or other reductants. Due to the stimulation of photo-catalytic TiO₂ by light, strong oxidants including oxygenic radicals such as HO· are formed to mineralize the organic pollutants deeply. This principle provides a basis for the quick and instantaneous measurement of organic pollutants. Meanwhile, the determination of total pollutants in the water can be achieved.The way in which photo-catalytic TiO₂ film was prepared and characterized was described in the paper. The mechanism of the photo-catalytic oxidation of organic substances by TiO₂ film was discussed and the brand new concept applied in the detection of COD by photo-catalytic oxidation was also offered. Furthermore, novel COD analyzer was developed. Totally, there are five chapters in this paper. The first chapterIn this part, four parts, that is, the development of the TiO₂ and their application and development in the environmental analysis. the oxidizing and catalytic mechanism of the nano-semiconductor and the research on the measurement of the oxygen containing radicals and the current circumstances of the development of the fast COD detector in the waste water system were discussed and a detail outline and review of the development in the current area was introduced.The second chapterThe method of Ti/TiO₂ photoelectrode prepared by using laser calcination method instead of oven calcination process was introduced. The prepared TiO₂ film was observed with AFM and XRD. Photoelectrocatalytic degradation of rhodamine B using this electrode was investigated, and anodic potential and pH were optimized. The laser power applied in this electrode preparation was also discussed, and it indicated that TiO₂ particle prepared with high laser power was crystallized adequately and the photoelectrocatalytic ability was satisfactory. RB degradation was investigated under different conditions, and it showed that photoelectrocatalytic degradation could achieve efficient and complete mineralization of organic pollutant. The photoelectrocatalytic oxidation using the Ti/TiO₂ electrode calcinated by laser was compared with that of the electrode calcinated by furnace, and it showed that the reaction rate of RB degradation using the electrode by laser was faster than that by furnace.The third chapterA Ti/TiO₂ mesh electrode by laser calcination was prepared in this article. The resulting TiO₂ film was investigated by X-ray diffraction （XRD） and electrochemical impedance spectroscopy （EIS）, and it illuminated that the prepared electrode mainly consisted of anatase TiO₂ nanoparticles on its surface and exhibited a superior photocatalytic activity. The photodegradation of methylene blue （MB） using the proposed electrode under different experimental conditions was investigated in terms of both UV absorbance at 664 run and chemical oxygen demand （COD） removal. The electrical bias applied in photoelectrocatalytic （PEC） oxidation was also studied. Through the comparison between photocatalytic （PC） oxidation and photoelectrocatalytic （PEC） oxidation, it was found that PEC oxidation was a convenient and effective way to mineralize the organic matters and that laser- treated photoelectrode exceeded the oven-treated one.The fourth chapterIn this chapter, a COD measurement by a photocatalytic oxidation method using nano TiO₂ film was studied. TiO₂ was deposited on a quartz support, which could avoid the filtration and provide higher quantum yields than TiO₂ in powder form. In addition, K₂Cr₂O₇ was used as electron scavenger, which could inhibit the recombination of electrons and holes and enhance the oxidation of organic compounds. The change in Cr（III） concentration produced by the photocatalytic reduction was measured by a colorimetric method. It was considered that the value obtained by the proposed method could be reliably correlated with the COD obtained by using the conventional methods.The fifth chapterIn this chapter, Ti/TiO₂ electrode was prepared by using laser-assisted sol-gel method, which could shorten the time of electrode preparation. And it was examined through characterization with XRD and photoelectrochemical behavior study with EIS and amperometry. The proposed electrode was developed as a sensor for the determination of COD. This method was proved to be simple, rapid and environmentally friendly. Additionally, the COD values obtained by the proposed method were well correlated with those obtained from the conventional method.The sixth chapterIn this chapter, photoelectro-synergistic catalysis oxidation of organics in the water on Ti/TiO₂/PbO₂ electrode was investigated by the method of electrochemistry. Furthermore, the results were compared with those obtained from photocatalysis and electrocatalysis. The method proposed was applied to determine the chemical oxygen demand （COD） value, Ti/TiO₂/PbO₂ electrode functioning as the work electrode during the process. It was shown that the method of photoelectro-synergistic catalysis had lower detection limit and wider linear range than the methods of electroassisted photocatalysis and electrocatalysis. The results obtained by the proposed method and conventional one were compared by carrying out the experiment on Wastewater samples. The correlation of the results using different methods was satisfactory and the relative bias was below ± 6.0 %. The seventh chapterA fast COD flow injection analysis （FIA） instrument by means of electroanalysis which was developed according to the photoelectro-synergistic catalysis theory of the Ti/TiO₂/PbO₂ electrode. This instrument has such advantages as the short detective time of the single sample, convenient operation, high precision, good consistency with the standard COD analytical method,less second pollution and the capability of fast COD analysis.更多还原