【作者】 刘松翠；

【导师】 邓克俭；

【作者基本信息】 中南民族大学 ， 物理化学， 2008， 硕士

【摘要】 众多研究表明,半导体TiO₂光催化能使许多有机物发生降解或彻底分解。因此,该技术在环境污染控制领域将具有巨大的经济和社会效益。本论文研究内容的选择是基于以下事实:第一、在二氧化钛光催化方面,国内外学者研究最多的是锐钛矿和金红石型二氧化钛,而纯的板钛矿型二氧化钛因为难以制备所以对它的报道较少。一般认为锐钛矿型二氧化钛的光活性高于金红石型,但也有文献报道金红石的光活性大于锐钛矿。板钛矿在某些环境中的光活性,相当于或强于锐钛矿型二氧化钛,但也有相反的报道。造成这种文献结论相互矛盾的原因,是影响二氧化钛光活性因素的多样性导致的。二氧化钛的光活性除受到晶型的影响外,还受到二氧化钛的纯度、晶粒尺寸的大小,比表面积、表面羟基和溶液的pH值等因素的影响,且这些影响因素相互依存和干扰。以上这些原因,导致了文献在评价不同晶型二氧化钛光活性方面结论不完全一致,乃至相互矛盾。第二、从目前提高二氧化钛光活性方面的研究结果来看,表面氟离子修饰最让人激动。有文献报道,氟离子修饰能大幅度提高锐钛矿型二氧化钛的光催化活性,而对金红石型二氧化钛的光活性则没有促进作用。氟离子修饰对板钛矿型二氧化钛光活性的影响,还没有文献报道。对该课题的研究,将会进一步丰富二氧化钛光催化体系的理论。针对以上问题,我们做了以下工作:第一、（论文第二章）为尽可能避免除晶型外影响因素的干扰,本论文选用同一种方法（水热合成法）批量制备了三种不同晶型TiO₂,并以难生物降解的活性染料X3B为目标分子,系统地比较了三种晶型TiO₂的光催化活性。发现钛源和水热pH值都对TiO₂的晶型都有重要的影响;三种晶型TiO₂的相对光活性次序为:锐钛矿（AT）>>金红石（RT）>>板钛矿（BT）型TiO₂。研究结论说明,催化对紫外光的吸收能力以及对有机污染物的表面吸附能力,是产生上述三种晶型二氧化钛光活性差异的原因之一。第二、（论文第三章）系统考察了氟离子表面修饰对在不同温度焙烧的板钛矿型二氧化钛光活性的影响。发现在板钛矿型TiO₂的热处理过程中,其晶相转化过程为:板钛矿经历锐钛矿,最终转化为金红石型TiO₂;氟离子表面修饰对板钛矿型TiO₂光活性无促进作用。更多还原

【Abstract】 Photocatalytic technology based on TiO₂ has provided an effective and promising means for remediation of environmental pollutants in air and water. Among the three polymorph phases of TiO₂, i.e. anatase, rutile and brookite, only the first two have been widely studied and their photoactivity was tested and compared. It was generally accepted that the photoreactivity of anatase was better than that of rutile. On the contrary, only a few recent papers dealing with the photoreactivity of pure brookite owing to the difficulties of obtaining its pure form, though it seems to have marked photocatalytic activity （comparable to anatase）. Contrary conclusions were usually drawn in the literatures on the relative photoreactivity of the three types TiO₂. The photoreacitivty of TiO₂ was a complex function of the phase, purity, particle size, specific surface area, density of surface hydroxyl groups of TiO₂, and solution pH. These parameters above usually interfere with each other.In the second part of the thesis, three type of TiO₂ were prepared on a large scale through hydrothermal treatment of Ti（SO4）2 or TiCl4 at certain pH. The photooxidation activity evaluated from the photocatalytic degradation of X3B , an anionic organic dye , revealed that the relative photoreactivity of the TiO₂ samples was as follows : AT >> RT >>BT , which is consistant with the adsorption ability of the catalysts. The reasons that caused the differences in photoreactivity among the three types TiO₂ were also discussed.Among various efforts for improvement of photocatalytic efficiency, the surface modification of TiO₂ by fluoride seems mostly interesting. Several studies have shown that surface modification of anatase TiO₂ can result in significant enhancement in the photocatalytic degradation of organic pollutants. However, the effects of fluoride surface modification in brookite TiO₂ has not been reported, which deserves to be investigated. In the third part of the thesis, the phase transformation of brookite as the sintering temperature increase, and the effects of fluoride on the photoreactivity of the sintered brookite TiO₂ were studied. It was found that brookite was transformed to rutile via anatase as the sintering temperature increase, but the photoreactivity of brookite TiO₂ decreased in the presence of fluoride.更多还原