The effect of UV absorption on the photocatalytic oxidation of 2-nitrophenol and 4-nitrophenol
The effect of UV absorption on the photocatalytic oxidation of 2-nitrophenol and 4-nitrophenol
复制标题
紫外吸收对2-硝基苯酚和4-硝基苯酚光催化氧化的影响
DOI：
--
复制
发表时间：
2005
期刊：
影响因子：
--
通讯作者：
J.W. Wang
中科院分区：
文献类型：
--
作者：
T. Egerton;P. Christensen;R. Harrison;J.W. Wang
测量了二氧化钛对 2-硝基苯酚和 4-硝基苯酚的吸附，并通过 HPLC 分析和测量溶液的总有机碳含量来跟踪它们的光催化氧化。氧化遵循伪一级动力学，速率常数随着硝基苯酚浓度的增加而减小。然而，即使反应中间体的相对量仍然很低，从反应动力学推断的吸附常数与吸附实验中测量的吸附常数不一致。我们得出的结论是，速率常数的降低不能用 Langmuir-Hinshelwood 模型来解释。相反，我们认为硝基酚的强烈但不同的紫外线吸收降低了催化剂表面的有效紫外线通量，并且更浓的溶液的更大吸收是速率常数明显降低的主要原因。对这种吸收的简单处理足以描述观察到的速率变化。紫外线吸收的定量效果取决于灯和反应器光学器件。他认为，差异既是报告的两种异构体相对氧化速率差异的原因，也是报告的有关 pH 对氧化速率影响的不同结论的原因。
Adsorption of 2-nitrophenol and 4-nitrophenol by titanium dioxide was measured and their photocatalytic oxidation was followed by both HPLC analysis and measurement of the total organic carbon content of the solution. The oxidation follows pseudo-first order kinetics with rate constants that decrease as the nitrophenol concentration increases. However the adsorption constants inferred from the reaction kinetics are inconsistent with those measured in the adsorption experiments, even though the relative amounts of reaction intermediates remain low. We conclude that the decrease in rate constant cannot be explained by a Langmuir–Hinshelwood model. Instead we suggest that the strong, but differing, UV absorption by nitrophenols lowers the effective UV flux at the catalyst surface and that the greater absorption of more concentrated solutions is primarily responsible for the apparent decrease in rate constant. A simple treatment of this absorption adequately describes the observed changes in rate. The quantitative effect of UV absorption depends on the lamp and on the reactor optics. It his suggested that variations are responsible both for differences in the reported relative oxidation rates of the two isomers, and for the different conclusions reported with respect to the effect of pH on oxidation rate.