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首页> 外文学位 >Development of Novel Visible and Solar Light-Activated Nanostructured Nitrogen-Fluorine Titanium Dioxide Photocatalyst for the Removal of Cyanotoxins in Water.
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Development of Novel Visible and Solar Light-Activated Nanostructured Nitrogen-Fluorine Titanium Dioxide Photocatalyst for the Removal of Cyanotoxins in Water.

机译：新型可见光和太阳光激活的氮氟氮钛二氧化钛光催化剂用于去除水中的氰毒素的研究。

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摘要

The prevalent and increasing occurrence of cyanobacteria and their toxins, known as cyanotoxins, in drinking water sources have become a potential health risk to humans. Physical treatment methods in conventional drinking water treatment have the capacity to remove cyanotoxins but are limited to a merely physical separation, where further treatment is required. Cyanotoxins are susceptible to chemical oxidation and recently advanced oxidation technologies (AOTs) and nanotechnologies (AONs), such as titanium dioxide (TiO2) photocatalysis, have been proven an effective alternative technology to chemically transform cyanotoxins in water. However, conventional TiO2 is restricted to UV light photoactivation for the generation of highly reactive oxygen species (i.e., hydroxyl radicals) representing an economical and technological limitation for the use of renewable energy sources such as solar light, since UV radiation accounts only for 5% of the total solar spectrum compared to the visible spectrum (∼45%). This dissertation explored the development of nanostructured nitrogen and fluorine co-doped TiO2 (NF-TiO2) that can be activated under visible and solar light for the photocatalytic degradation of cyanotoxins in water. This work aimed to develop highly efficient NF-TiO2 nanoparticles and films to evaluate the environmental fate of microcystins, the most widespread and highly persistent group of cyanotoxins found in surface waters, and cylindrospermopsin which has emerged as the most significant toxin in freshwater sources. Specific attention was given to 1) the fundamental aspects on the synthesis method that influenced the physicochemical properties of NF-TiO2, such as the incorporation of nitrogen and fluorine in the structure of TiO 2 and the synergistic effects induced by both dopants, 2) the surface interaction between the cyanotoxins and NF-TiO2 in different water matrix, 3) the reactivity and degradation kinetics of microcystins and cylindrospermopsin with NF-TiO2 and 4) the mechanism of radical formation with NF-TiO 2 under visible and solar light. The existence of interstitial nitrogen and substitutional fluorine in the NF-TiO2 lattice was determined and the formation of localized intra-gap states was established implying that fluorine promotes nitrogen incorporation in TiO2. A shift in the absorbance capacity of NF-TiO2 in the visible range was also observed. Anatase/brookite heterojunctions, which promote photocatalytic efficiency, were found in NF-TiO2. High initial degradation rates for microcystin-LR (MC-LR) were obtained with NF-TiO2 nanoparticles and films in synthetic water under visible light. The effect of pH indicated that attractive forces at acidic conditions between the oppositely charged NF-TiO2 and MC-LR contributed to higher MC-LR initial degradation rates. The presence of alkalinity and natural organic matter had a scavenging effect since the initial MC-LR degradation rates decreased. Modifications to NF-TiO2 with Evonik Aeroxide® P25-TiO2 (P25) nanoparticles lead to composite NF-TiO2-P25 with improved photocatalytic activity towards MC-LR, MC-RR, MC-YR, MC-LA and cylindrospermopsin under visible and UV-vis light. The general reactivity was MC-LA>MC-LR≥MC-YR>MC-RR. Finally, results using selected scavengers indicate that the main mechanism of NF-TiO 2 radical formation under visible light irradiation differed from UV-mediated TiO2 photocatalysis since no evidence of hydroxyl radical production from the surface holes was observed. It was suggested that under visible light, surface oxygen reduction of NF-TiO2 occurred to form superoxide radical anion as main radical specie. The affinity of the scavenger with NF-TiO 2 and MC-LR in terms of pH was established as an important parameter to determine the radicals formed in this study.
机译：在饮用水源中，蓝细菌及其毒素（称为蓝毒素）的流行和增加的发生已成为人类潜在的健康风险。传统饮用水处理中的物理处理方法具有去除氰毒素的能力，但仅限于物理分离，需要进一步处理。氰毒素容易受到化学氧化的影响，近来先进的氧化技术（AOT）和纳米技术（AON），例如二氧化钛（TiO2）光催化已被证明是化学转化水中的毒素的有效替代技术。然而，常规的TiO2限于UV光的光活化以生成高反应性的氧类（即羟基自由基），这代表了使用可再生能源（例如太阳光）的经济和技术限制，因为UV辐射仅占5％。总太阳光谱的可见光谱（约45％）。本论文探索了可以在可见光和太阳光下活化的氮和氟共掺杂纳米TiO2（NF-TiO2）的开发，用于光催化降解水中的毒素。这项工作旨在开发高效的NF-TiO2纳米颗粒和薄膜，以评估微囊藻毒素，地表水中发现的最广泛和最持久的一组氰毒素和环精胺蛋白酶的环境命运，而环孢菌精则已成为淡水源中最重要的毒素。应特别注意1）影响NF-TiO2物理化学性质的合成方法的基本方面，例如在TiO 2的结构中掺入氮和氟以及两种掺杂剂引起的协同效应，2）氰毒素与NF-TiO2在不同水基质中的表面相互作用; 3）微囊藻毒素和环精皮蛋白酶与NF-TiO2的反应和降解动力学; 4）可见光和太阳光下NF-TiO 2自由基形成的机理。确定了在NF-TiO2晶格中存在间隙氮和取代氟，并建立了局部能隙状态的形成，这暗示氟促进了氮在TiO2中的掺入。还观察到了NF-TiO 2的吸收能力在可见范围内的变化。在NF-TiO2中发现了促进光催化效率的锐钛矿/板钛矿异质结。在可见光下，使用合成水中的NF-TiO2纳米颗粒和薄膜可获得微囊藻毒素-LR（MC-LR）的高初始降解率。 pH值的影响表明，在酸性条件下，带相反电荷的NF-TiO2和MC-LR之间的吸引力会导致较高的MC-LR初始降解速率。由于初始MC-LR降解速率降低，因此碱度和天然有机物的存在具有清除作用。用赢创Aeroxide®P25-TiO2（P25）纳米粒子对NF-TiO2进行改性，导致复合NF-TiO2-P25在可见光和紫外光下具有对MC-LR，MC-RR，MC-YR，MC-LA和圆筒型精原藻的光催化活性。 -可见光。总体反应性为MC-LA>MC-LR≥MC-YR> MC-RR。最后，使用选定的清除剂的结果表明，可见光照射下NF-TiO 2自由基形成的主要机理不同于UV介导的TiO2光催化，因为没有观察到表面空穴产生羟基自由基的迹象。提示在可见光下，NF-TiO2的表面氧还原发生，形成超氧自由基阴离子作为主要自由基。建立了清除剂与pH值相关的NF-TiO 2和MC-LR的亲和力，作为确定该研究中形成的自由基的重要参数。

著录项

  • 作者

    Pelaez, Miguel.;

  • 作者单位

    University of Cincinnati.;

  • 授予单位 University of Cincinnati.;
  • 学科 Engineering Environmental.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 204 p.
  • 总页数 204
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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