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以纳米二氧化钛(TiO2)光催化降解甲醛, 使用2-甲基-2-亚硝基丙烷(2-methyl-2-nitroso-propane, MNP)作为自旋捕截剂(spin trap, ST), 研究了反应过程中的自由基中间体, 得到了一种新的自旋加合物(spin adduct, ST-R). 电子顺磁共振(Electron Paramagnetic Resonance, EPR)的结果表明, 甲醛在水溶液中降解的反应中间体为8226;CH(OH)2, 并提出了一种新的降解机理. 相似文献
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纳米TiO_2对水中腐殖酸的吸附及光催化降解 总被引:1,自引:0,他引:1
研究了水体中腐殖酸 ( HA)在纳米 Ti O2 颗粒上的吸附行为 ,并探讨了其吸附机理 ,还研究了 HA的Ti O2 光催化降解效果 .结果表明 ,Ti O2 对 HA的吸附作用明显依赖于水溶液的 p H,也取决于 Ti O2 的零电荷点 ;HA的光催化降解效果与其在催化剂表面的吸附行为密切相关 ,提高吸附速率 ,HA的去除率也随之提高 ;增加催化剂用量也能改善降解程度 相似文献
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以具有新型多级孔中空薄壳结构的ZSM-5分子筛(Gel-ZSM-5)作为催化剂,正十六烷作为探针分子,研究了催化剂的孔道结构及酸性对大分子催化裂化反应的影响.实验结果表明,该催化剂中的介孔、大孔多级结构非常有利于大分子反应物、中间产物以及结焦物在其表面及内部的快速传输,从而大幅提高催化转化率并延长了催化剂寿命;另外,催化剂多级孔表面的大量酸性位点可以显著提高针对大分子的催化反应性能,并且明显改善了产物的选择性.在较短的反应时间下,这种构效关系体现得更加显著.因此,合理的酸性分布和多级中空薄壳孔道结构将赋予催化剂在大分子催化裂化中具有更好的催化活性、选择性及更长的催化寿命,为设计新型高效催化剂提供了依据. 相似文献
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纳米尺度分散的TiO2光催化降解甲醛的机理 总被引:11,自引:0,他引:11
纳米TiO2具有小尺寸效应,表面效应和宏观量子隧道效应等[1],广泛用于防水处理、空气净化、抗菌防霉等方面。本文对其能带结构及其消除甲醛的性能及机理进行分析。1 纳米TiO2光催化剂1 1 制备与表征以四氯化钛为主要原料,氨水、醇类化合物、盐酸等为主要反应助剂,采用亚稳态氯化法制备工艺,用相应的溶胶反应形成溶胶液体,低于100℃加热该液体,除去多余的水分,得到溶胶-凝胶体。过滤所得溶胶-凝胶体,并用蒸馏水反复洗涤数次,使其pH呈中性。将洗涤后的溶胶-凝胶体进行真空干燥,得到白色微粉,1000℃高温煅烧,将煅烧后得到的纳米TiO2基… 相似文献
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利用酸性蓝BGA染料敏化的纳米TiO2作为光催化剂, 与低密度聚乙烯(LDPE)树脂复合制备了具有可见光催化降解性能的复合塑料薄膜. 采用SEM、FTIR、VHX-100数码显微镜和高温凝胶渗透色谱(HTGPC)等分析技术系统地研究了该塑料薄膜在紫外光和太阳光照射下的降解性能. 探讨了塑料薄膜在光辐照前后的力学性能、质量和分子量变化规律. 研究结果表明, 该薄膜在经紫外线照射5 d后质量损失达到17.6%, 数均分子量由21800降低为5900; 经太阳光照射48 d后质量损失达到12.5%, 分子量降为8100. 辐照后薄膜拉伸强度和断裂伸长率显著降低, 羰基含量升高. 相似文献
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掺铈纳米TiO2薄膜制备及光催化降解甲醛甲苯 总被引:11,自引:0,他引:11
通过Sol-Gel工艺在玻璃表面及多孔陶瓷表面制得了均匀透明的掺铈纳米TiO2薄膜.通过SEM、XRD及UV-Vis等手段对玻璃表面掺铈纳米TiO2薄膜进行了表征.结果表明,薄膜表面无开裂现象、膜内部比表面积大、TiO2分布均匀.薄膜中出现的锐钛矿相在(101)面有一定的择优取向,且UV-Vis研究表明,掺铈纳米TiO2薄膜在近紫外的吸光度有明显提高.利用自行设计的反应器,以多孔陶瓷为介质,对甲醛、甲苯等有机物进行了光催化降解研究.结果表明,掺铈纳米TiO2薄膜对甲醛甲苯有极高的光催化降解效率,由于薄膜成本低廉,易于工业化,为净化室内空气开辟了新的途径. 相似文献
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Lead dioxide electrodes on Ti substrates were prepared by thermal-deposition or electro-deposition. The amount of hydroxyl radicals generated at the electrodes prepared by the above-mentioned two methods was compared with that at the electrodes mingled with Bi or La prepared by electro-deposition. The experimental results indicate that the highest concentration of hydroxyl radicals generated by thermal-deposition, electro-deposition mingled with nothing, electro-deposition mingled with Bi or La was 0.781, 1.048, 1.838 or 2.044 μmol/L, respectively. When phenol was electrolyzed on the four electrodes at a current density of 30 mA/cm2, the removal efficiency of phenol after electrolysis for 1.5 h was 87.30%, 93.55%, 97.95% or 98.70%, TOC removal efficiency after electrolysis for 5 h was 86.76%, 94.26%, 98.53% or 99.60%, respectively. Through the degradation experiments of phenol, the amount of hydroxyl radicals was responsible for the removal efficiency of phenol. The electro-catalytic characteristics were investigated by SEM, the generation amount of hydroxyl radicals, the degradation degree of phenol and the stability and conductivity of the electrodes were also investigated. The experimental results indicate that the four electrodes all show good electro-catalytic characteristics; the electro-catalytic characteristics of the electrode mingled with La were superior to those of the other three ones, and the electrochemical degradation of phenol followed one-step reaction dynamics. 相似文献
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LIU Wei-min 《高等学校化学研究》2013,29(2):314-318
An activated foam-structured carbon-ceramic(AFCC) was prepared and investigated as TiO2 support for the photocatalytic degradation of phenol. AFCC and TiO2/AFCC catalysts were characterized by N2 adsorption- desorption and X-ray diffraction(XRD). The effects of AFCC on the photocatalytic activity and the crystallinity of TiO2 were studied. The results show that the crystallinity and anatase/rutile ratio of TiO2 loaded on AFCC could be significantly influenced by the calcination temperature. The degradation rate of phenol benefited from the synergistic effects of the adsorption of activated carbon(AC) and the photocatalysis of TiO2, which suggests that a high surface area of AC is essential to achieve high degradation rates and efficiencies. It was found that the larger mean cell size of AFCC increased the light transmission within the foam. 相似文献
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以硝酸钕和钛酸四正丁酯作为前驱体,采用溶胶-凝胶法制备了Nd2O3/TiO2纳米光催化剂,并通过XRD和BET等手段进行了表征.以对苯二甲酸作为探针分子,结合化学荧光技术研究了光催化剂表面羟基自由基的生成;并以甲基橙为光催化降解反应模型化合物,考察了光催化剂的活性.测定了甲基橙在TiO2和Nd2O3/TiO2(1.0%)光催化剂上的吸附常数.结果表明:Nd2O3掺杂使TiO2的粒径减小,比表面积增大;羟基自由基的生成速率越大,催化剂的催化活性越高.Nd2O3掺杂有利于反应底物在催化剂表面的吸附,Nd2O3的最佳掺入量为Nd/Ti(摩尔比)=1.0%. 相似文献
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采用原位插层法制备了CdS-TiO2/累托石纳米复合材料. 以X射线粉未衍射、电镜、红外光谱、漫反射吸收光谱及液氮吸附比表面积测定等方法对其微结构和性能进行了分析与表征. 并以罗丹明B(RB)为模拟有机污染物, 对比研究了累托石、TiO2/累托石与CdS-TiO2/累托石的吸附和光催化性能. 结果表明, 与累托石相比, CdS-TiO2/累托石具有更复杂的多孔结构、更大的孔体积和比表面积以及更有效的光吸收能力; 该类复合材料表现出良好的吸附性能和光催化降解活性. 相似文献
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Fourier Transform EPR Spectroscopy of Trityl Radicals for Multifunctional Assessment of Chemical Microenvironment
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Dr. Andrey A. Bobko Dr. Ilirian Dhimitruka Prof. Dr. Jay L. Zweier Prof. Dr. Valery V. Khramtsov 《Angewandte Chemie (International ed. in English)》2014,53(10):2735-2738
Pulse techniques in electron paramagnetic resonance (EPR) allow for a reduction in measurement times and increase in sensitivity but require the synthesis of paramagnetic probes with long relaxation times. Here it is shown that the recently synthesized phosphonated trityl radical possesses long relaxation times that are sensitive to probe the microenvironment, such as oxygenation and acidity of an aqueous solution. In principle, application of Fourier transform EPR (FT‐EPR) spectroscopy makes it possible to acquire the entire EPR spectrum of the trityl probe and assess these microenvironmental parameters within a few microseconds. The performed analysis of the FT‐EPR spectra takes into consideration oxygen‐, proton‐, buffer‐, and concentration‐induced contributions to the spectral shape, therefore enabling quantitative and discriminative assessment of pH, pO2, and concentrations of the probe and inorganic phosphate. 相似文献
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Au/TiO2光催化剂的制备及其催化性能 总被引:2,自引:0,他引:2
采用改进的等体积浸渍法、光化学沉积法分别制备了不同Au担载量的Au/TiO2光催化剂,以甲基橙的光催化降解反应作为模型反应,考察了金的担载量、预处理条件、制备方法等因素对其光催化性能的影响,以漫反射紫外一可见光谱(DRS)分析了不同金担载量的Au/TiO2光催化剂的光谱特征。结果显示,适当担载量的Au可显著提高TiO2的光催化活性,以改进的等体积浸渍法制备的0.8%Au/TiO2催化剂的光催化活性最高。DRS结果显示,金的担载对TiO2的光谱特征没有影响。 相似文献
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Kiss M. Könczöl F. Farkas N. Lőrinczy D. Belagyi J. 《Journal of Thermal Analysis and Calorimetry》2001,65(2):627-637
The effect of free radicals obtained in hydroxyl and cerium(IV)-nitrilotriacetic acid free radical generating systems on contractile
proteins (actin, myosin and their complexes in glycerinated muscle fibres) was studied using differential scanning calorimetry
and spin trapping electron paramagnetic resonance technique. The analysis of spectra showed that selective attack of thiol
groups – Cys-257 and Cys-374 residues of actin, and among others Cys-707 residue of myosin – and random attack of sidechains
of the main proteins of muscle tissue produced structural and functional changes, which affected the ATP hydrolysis cycle
and very likely the dynamics of actin. The melting curves obtained on protein systems support the view that global conformational
changes accompany the local damage of free radicals.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献