Use of selected scavengers for the determination of NF-TiO2 reactive oxygen species during the degradation of microcystin-LR under visible light irradiation
Use of selected scavengers for the determination of NF-TiO2 reactive oxygen species during the degradation of microcystin-LR under visible light irradiation
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DOI：
10.1016/j.molcata.2016.09.035
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发表时间：
2016-12-15
影响因子：
--
通讯作者：
Dionysiou, Dionysios D.
中科院分区：
文献类型：
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作者：
Pelaez, Miguel;Falaras, Polycarpos;Dionysiou, Dionysios D.
虽然UV诱导的TiO 2光催化涉及几种活性氧（ROS）的产生，羟基自由基的形成通常与水中持久性有机污染物的降解有关。在这项研究中，各种自由基清除剂的歧视的作用，不同的活性氧在可见光激活（VIA）的光催化降解过程中使用氮和氟掺杂的二氧化钛（NF-二氧化钛）在水中的肝毒素，微囊藻毒素-LR（MC-LR）。在可见光下，在pH 3.0下，向反应混合物中添加羟基自由基清除剂、甲醇和叔丁醇导致对NF-TiO 2光催化降解MC-LR的可忽略的”抑制“，而在pH 5.7下仅部分抑制。虽然羟基自由基（“OH”）通常在UV-TiO 2光催化降解中起主要作用，但在这些实验条件下，MeOH和t-BuOH对降解过程的影响最小，表明（OH）-O-中心点在VIA NF-TiO 2光催化降解中并不重要。然而，在超氧化物歧化酶，苯醌和过氧化氢酶的存在下，在pH 3.0和5.7的VIA NF-TiO 2光催化降解MC-LR观察到强烈的抑制，表明O-2（中心点-）和H2 O2在降解过程中发挥关键作用。在氧化氘存在下观察到类似的降解速率，其增强单线态氧介导的过程，进一步表明单线态氧不是MC-LR降解中的关键物质。分别加入甲酸和硝酸铜来探测价带空穴和导带电子的作用。在UV-vis光照射下，在pH 5.7的“OH”清除剂存在下，观察到NF-TiO 2几乎完全抑制MC-LR去除。这些结果表明，溶液pH值对VIA NF-TiO 2光催化过程中活性氧的形成和反应性起着重要作用。需要仔细考虑清除剂和MC-LR在NF-TiO 2上的吸附强度以及作为pH值函数的ROS形态，因为它们在该过程的效率中也起着重要作用。这些结果表明，VIA NF-TiO 2光催化降解MC-LR的关键因素是光生电子还原分子氧，而不是光生空穴氧化反应产生的羟基自由基。(C)2016爱思唯尔B. V.保留所有权利。
Although UV-induced TiO2 photocatalysis involves the generation of several reactive oxygen species (ROS), the formation of hydroxyl radicals is generally associated with the degradation of persistent organic contaminants in water. In this study, a variety of radical scavengers were employed to discriminate the roles of different ROS during visible light-activated (VIA) photocatalysis using nitrogen and fluorine doped TiO2 (NF-TiO2) in the degradation of the hepatotoxin, microcystin-LR (MC-LR) in water. The addition of hydroxyl radical scavengers, methanol and tert-butyl alcohol to the reaction mixture resulted in negligible" inhibition of NF-TiO2 photocatalytic degradation of MC-LR at pH 3.0 and only partial inhibition at pH 5.7 under visible light. While hydroxyl radicals ("OH) generally play the primary role in UV-TiO2 photocatalysis, the minimal influence of MeOH and t-BuOH on the degradation process under these experimental conditions indicates that (OH)-O-center dot are not crucial in VIA NF-TiO2 photocatalysis. However, strong inhibition was observed in VIA NF-TiO2 photocatalytic degradation of MC-LR in the presence of superoxide dismutase, benzoquinone and catalase at pH 3.0 and 5.7 indicating that O-2(center dot-) and H2O2 play critical roles in the degradation process. Similar degradation rates were observed in the presence of deuterium oxide, which enhances singlet oxygen mediated processes further suggesting singlet oxygen is not a key species in the degradation of MC-LR. Formic acid and cupric nitrate were added to probe the roles of the valence band holes and conduction band electrons, respectively. Under UV-vis light irradiation, almost complete inhibition of MC-LR removal is observed with NF-TiO2 in the presence of "OH scavengers at pH 5.7. These results demonstrate that the solution pH plays a major role in the formation and reactivity of ROS during VIA NF-TiO2 photocatalysis. The adsorption strength of scavengers and MC-LR onto NF-TiO2 as well as the speciation of ROS as a function of pH needs to be carefully considered since they also play a major role in the efficiency of the process. These results indicate that the reduction of molecular oxygen by photo-generated electrons rather than hydroxyl radicals produced by oxidative reactions of photo-generated holes is the key factor in the VIA NF-TiO2 photocatalytic degradation of MC-LR. (C) 2016 Elsevier B.V. All rights reserved.