Choi Hyeok, Antoniou Maria G, Pelaez Miguel, De la Cruz Armah A, Shoemaker Jody A, Dionysiou Dionysios D
Department of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio 45221-0071, USA.
Environ Sci Technol. 2007 Nov 1;41(21):7530-5. doi: 10.1021/es0709122.
The presence of the harmful cyanobacterial toxins in water resources worldwide drives the development of an innovative and practical water treatment technology with great urgency. This study deals with two important aspects: the fabrication of mesoporous nitrogen-doped TiO2 (N-TiO2) photocatalysts and their environmental application for the destruction of microcystin-LR (MC-LR) under visible light. In a nanotechnological sol-gel synthesis method, a nitrogen-containing surfactant (dodecylammonium chloride) was introduced as a pore templating material for tailor-designing the structural properties of TiO2 and as a nitrogen dopant for its visible light response. The resulting N-TiO2 exhibited significantly enhanced structural properties including 2-8 nm mesoporous structure (porosity 44%) and high surface area of 150 m2/g. Red shift in light absorbance up to 468 nm, 0.9 eV lower binding energy of electrons in Ti 2p state, and reduced interplanar distance of crystal lattices proved nitrogen doping in the TiO2 lattice. Due to its narrow band gap at 2.65 eV, N-TiO2 efficiently degraded MC-LR under visible spectrum above 420 nm. Acidic condition (pH 3.5) was more favorable for the adsorption and photocatalytic degradation of MC-LR on N-TiO2 due to electrostatic attraction forces between negatively charged MC-LR and +6.5 mV charged N-TiO2. Even under UV light, MC-LR was decomposed 3-4 times faster using N-TiO2 than control TiO2. The degradation pathways and reaction intermediates of MC-LR were not directly related to the energy source for TiO2 activation (UV and visible) and nature of TiO2 (neat and nitrogen-doped). This study implies a strong possibility for the in situ photocatalytic remediation of contaminated water with cyanobacterial toxins and other toxic compounds using solar light, a sustainable source of energy.
全球水资源中有害蓝藻毒素的存在，使得开发一种创新且实用的水处理技术变得极为迫切。本研究涉及两个重要方面：介孔氮掺杂二氧化钛（N-TiO₂）光催化剂的制备及其在可见光下对微囊藻毒素-LR（MC-LR）破坏的环境应用。在一种纳米技术的溶胶-凝胶合成方法中，引入了一种含氮表面活性剂（十二烷基氯化铵），作为用于定制设计TiO₂结构特性的孔模板材料，以及作为其可见光响应的氮掺杂剂。所得的N-TiO₂表现出显著增强的结构特性，包括2-8nm的介孔结构（孔隙率44%）和150m²/g的高比表面积。光吸收红移至468nm，Ti 2p态电子的结合能降低0.9eV，以及晶格面间距减小，证明了TiO₂晶格中存在氮掺杂。由于其2.65eV的窄带隙，N-TiO₂在420nm以上的可见光谱下能有效降解MC-LR。酸性条件（pH 3.5）因带负电的MC-LR与带+6.5mV电荷的N-TiO₂之间的静电吸引力，更有利于MC-LR在N-TiO₂上的吸附和光催化降解。即使在紫外光下，使用N-TiO₂分解MC-LR的速度也比对照TiO₂快3-4倍。MC-LR的降解途径和反应中间体与TiO₂活化的能源（紫外光和可见光）以及TiO₂的性质（纯TiO₂和氮掺杂TiO₂）没有直接关系。本研究表明，利用太阳能（一种可持续能源）对受蓝藻毒素和其他有毒化合物污染的水进行原位光催化修复具有很大可能性。
