【作者】 张文皓；

【导师】 杨武； 高锦章；

【作者基本信息】 西北师范大学 ， 分析化学， 2007， 硕士

【摘要】 近年来,用纳米TiO₂等半导体光催化技术降解水中有机污染物的研究成为环境科学领域的一个热点。光催化技术具有常温、常压下进行,能彻底破坏有机污染物,无二次污染等优点。同时,纳米TiO₂自身也存在着一些不足,非常有必要对其进行合理的改性。本文以钛酸四丁酯为原料、冰醋酸为螯合剂、乙醇为溶剂,采用溶胶-凝胶法制备了纯的和掺杂铈的TiO₂纳米粒子,并利用XRD和UV-VIS对其进行表征,考察了不同煅烧温度对TiO₂纳米粒子晶型组成、粒径大小和光催化活性的影响,研究了TiO₂在煅烧过程中的相转变。在日光下,以亚甲基蓝的光催化降解为模型反应,研究不同培烧温度和掺杂量催化剂对光降解效率的影响。由于利用太阳光或紫外光线具有其局限性,本文通过溶胶—凝胶方法制得的二氧化钛催化剂与两种高级氧化技术—超声波降解技术、接触辉光放电电解技术联用,来考虑其在有机染料废水降解处理过程中的催化活性。研究结果表明,Ce的掺杂抑制了锐钛矿晶粒的生长,抑制了TiO₂在高温煅烧过程中从锐钛矿型向金红石型的转变,并使TiO₂纳米粒子的光谱响应围拓展到可见光区。Ce的掺杂浓度和煅烧温度对复合光催化剂的制备有显著影响。本实验通过单因素实验分析,获得了在Ce掺杂条件下最优实验条件:掺杂量为0.5%,煅烧温度为800℃,在此条件下,光降解效率得到较大提高。亚甲基蓝降解率随超声时间的增加而增加;溶液的pH值的变化对亚甲基蓝降解的影响不大,但是在中性溶液中,其降解率稍高于酸性或碱性溶液中。二氧化钛催化剂用量在450～500mg/L之间,超声波频率40 KHz,输出功率为50 W,pH为8.0,亚甲基蓝水溶液的初始浓度为20mg/L的条件下,60分钟左右降解率即可达到90%以上。在二氧化钛膜协同接触辉光放电电解技术降解亚甲基蓝废水实验中,镀膜5次所得薄膜具有高的催化性能:二氧化钛协同接触辉光放电可以高效的降解亚甲基蓝分子;所制的薄膜随使用次数的增加而活性变化不大。更多还原

【Abstract】 In recent years, the heterogeneous photocatalysis for the degradation of organic pollutants using nano-TiO₂ semiconductors has been extensively studied in environmental science. The photocatalytic degradation technique has many advantages, such as operating under ambient temperature and normal pressure, decomposing organic pollutants completely without second pollution. Except for those advantages, nano-TiO₂ powders have some deficiencies, so it is necessary to modify TiO₂ by the adulteration to improve their photocatalytic activity.The pure and Ce doped TiO₂ nanoparticles were prepared by a sol-gel method with Ti（0Bu）4 as raw material, HAc as complexagent and alcohol as the solvent, and characterized by XRD and UV-VIS. Influence of roasting temperature on the crystal phase composition, the particle size and the catalytic activity was also researched. In addition, the phase transition of the TiO₂ powder was studied in the roasting process. The photocatalytic activities of the prepared samples and the effect of doped Ce content on activities were investigated by the degradation reaction of methylene blue under the sunlight.The results showed the doped Ce could greatly restrain the increase of crystallite size and the change of crystal phase of TiO₂ in high calcinations temperature from anatase phase to rutile phase, and it also can extend the light response of TiO₂ nanoparticlcs to the visible region. The concentration of the doped Ce and calcination temperature showed remarkable effect to photodegradation. When the concentration of the Ce dopant was 0.5% and the calcination temperature was 800℃, prepared composition photocatalyst showed highest catalytic activity to methylene blue degradation.To improve further the degradation efficiency to methylene blue, the photocatalytic degradation of TiO₂ combined with other advanced oxidation technology - ultrasonic wave irradiation and contact glow discharge electrolysis was studied. A variety of affecting factors on ultrasonic degradation of methylene blue in the presence of sol-gel nano TiO₂ were studied. The results indicated that the degradation efficiency of methylene blue rose with the rise of reaction time. The initial pH of reaction solution had little influence to the degradationefficiency, but in alkali solution, methylene blue degraded easier than in acid or neutral solution. The degradation efficiency of methylene blue reached up to 92% in 60min when ultrasonic frequency was 40KHz, power input was 50W, amount of the catalyst 450～500mg/L, pH=8.0 and the initial dye concentration was 20mg/L.In the test of the degradation of methylene blue with nano-TiO₂ film combining with contact glow discharge electrolysis, it was found that when the number of layers is 5, the photocatalytic activity is highest. The developed new method can degrade methylene blue more efficiently. And the composition catalyst had long using life and could be used repetitiously.更多还原