Role of primary active species and TiO2 surface characteristic in UV-illuminated photodegradation of Acid Orange 7
Role of primary active species and TiO2 surface characteristic in UV-illuminated photodegradation of Acid Orange 7
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DOI：
10.1016/j.jphotochem.2004.11.006
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发表时间：
2005-05-15
影响因子：
4.3
通讯作者：
Lou, LP
中科院分区：
文献类型：
--
作者：
Chen, YX;Yang, SY;Lou, LP
关于光催化氧化是否通过 OH 中心点自由基、价带空穴、O-2（中心点-）或 H2O2 进行仍存在争议。本文研究了这些主要氧化剂在紫外照射的 TiO2 悬浮液中偶氮染料酸性橙 7 (AO7) 光降解中的作用。甲醇或异丙醇对降解的影响很小，表明氧化主要不是通过OH中心点自由基与AO7之间的反应进行的，因为醇可以有效地清除OH中心点自由基。但 I-（空穴清除剂）的存在显着抑制了降解，因此表明空穴发挥了主要作用。然后，在乙腈、甲醇或异丙醇溶剂中进行的实验证实了空穴的主要作用，因为OH中心点自由基在干燥溶剂中被最小化。此外，有人提出，当Cr(VI)代替O-2作为电子清除剂时，O-2(中心点-)和H2O2的影响可以忽略不计。还研究了 F- 或 SO42- 表面改性对光降解初始步骤的影响。 TiO2表面的羟基被F-或SO42-取代，几乎没有吸附的AO7分子被空穴捕获，因此初始过程可以逐渐从空穴主导的表面反应转向本体溶液中的均相自由基反应。对吸附与光降解之间关系的讨论表明，降解速率不受TiO2表面有机物实际位置量的强烈影响。 (c) 2004 Elsevier B.V. 保留所有权利。
Controversy still exists over whether photocatalytic oxidation proceeds via OH center dot radicals, valence band holes, O-2(center dot-) or H2O2, In this paper, the role of these primary oxidants in the photodegradation of an azo dye, Acid Orange 7 (AO7) in UV-illuminated TiO2 suspension was investigated. Little influence of methanol or isopropanol on the degradation indicated that the oxidation was not primarily proceeding by reaction between OH center dot radicals and AO7, because alcohols could effectively scavenge OH center dot radicals. But the presence of I- (hole scavenger) significantly inhibited the degradation, thus suggesting that holes played a major role. Then, experiments carried out in acetonitrile, methanol or isopropanol solvent confirmed the major role of holes, since OH center dot radicals were minimized in dry solvent. In addition, it was suggested that O-2(center dot-) and H2O2 had a negligible effect when Cr(VI) was used as electron scavenger instead of O-2. The effects of surface modification by F- or SO42- on the initial steps of photodegradation were also investigated. The hydroxyl groups on the surface of TiO2 were replaced by F- or SO42- and there were little adsorbed AO7 molecules to be trapped by hole, so the initial process could shift progressively from hole-dominated surface reaction to homogeneous radical reaction in bulk solution. Discussion about the relationship between adsorption and photodegradation indicated that the degradation rate was not strongly affected by the actual location amount of organics on TiO2 surface. (c) 2004 Elsevier B.V. All rights reserved.