Effects of TiO2 surface modifications on photocatalytic oxidation of arsenite:: The role of superoxides
Effects of TiO2 surface modifications on photocatalytic oxidation of arsenite:: The role of superoxides
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DOI：
10.1021/es034725p
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发表时间：
2004-05-15
影响因子：
11.4
通讯作者：
Choi, W
中科院分区：
文献类型：
--
作者：
Ryu, J;Choi, W
使用TiO 2光催化剂，亚砷酸盐[As（III）]可以快速氧化为砷酸盐[As（V）]，其在水环境中毒性较小且移动的较少。超氧化物最近已被提出作为As（III）的主要光催化氧化剂，而OH自由基是大多数TiO 2光催化氧化（PCO）反应中的主要氧化剂。这项研究证实，超氧化物是主要负责的As（III）PCO通过调查PCO动力学纯和改性TiO 2系统。As（III）氧化的速率急剧增加的Pt-TiO 2，这可以归因于通过有效的界面电子转移从导带（CB）的O-2的增强的超氧化物生成。由于加入叔丁醇（OH自由基清除剂）在裸和Pt-TiO 2悬浮液中对PCO速率的影响很小，OH自由基似乎不参与。此外，作为电子之间的TiO2 CB和O-2穿梭的聚氧乙烯酸盐（POM）高度促进PCO率，而单独的POM是不是有效的在所有氧化As（III）。氟化的二氧化钛，具有显着降低的吸附能力的As（III）没有显示出减少PCO率，这表明直接的空穴传输路径是不重要的。当使用染料敏化Pt-TiO 2时，亚砷酸盐氧化在可见光下进行，其速率与Pt-TiO 2/UV的情况相似。由于只有超氧化物可以产生作为光氧化剂在这个可见光系统中，它们的作用作为一个主要的氧化剂的As（III）的确认。此外，在超氧化物歧化酶的存在下，PCO率显着降低。
Using TiO2 photocatalyst, arsenite [As(III)] can be rapidly oxidized to arsenate [As(V)], which is less toxic and less mobile in the aquatic environment. Superoxides have been recently proposed as a main photocatalytic oxidant of As(III)whereas OH radicals are dominant oxidants in most TiO2 photocatalytic oxidation (PCO) reactions. This study confirms that superoxides are mainly responsible for the As(III) PCO by investigating PCO kinetics in pure and modified TiO2 systems. The rate of As(III) oxidation drastically increased on Pt-TiO2, which could be ascribed to the enhanced superoxide generation through an efficient interfacial electron transfer from the conduction band (CB) to O-2. Since the addition of tert-butyl alcohol (OH radical scavenger) had little effect on the PCO rate in both naked and Pt-TiO2 suspensions, OH radicals do not seem to be involved. The addition of polyoxometalates (POMs) as an electron shuttle between TiO2 CB and O-2 highly promoted the PCO rate whereas the POM alone was not effective at all in oxidizing As(III). Fluorinated TiO2 that had a markedly reduced adsorptive capacity for As(III) did not show a reduced PCO rate, which indicates that the direct hole transfer path is not important. The arsenite oxidation proceeded under visible light with a similar rate to the case of Pt-TiO2/UV when dye-sensitized Pt-TiO2 was used. Since only superoxides can be generated as a photooxiclant in this visible light system, their role as a main oxidant of As(III) is confirmed. In addition, the PCO rate was significantly reduced in the presence of superoxide dismutase.