Iodine-sensitized degradation of 2,4,6-trichlorophenol under visible light.
Iodine-sensitized degradation of 2,4,6-trichlorophenol under visible light.
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DOI：
10.1021/es301577p
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发表时间：
2012-08
影响因子：
11.4
通讯作者：
Meiqing Hu;Y. Wang;Z. Xiong;Dongqin Bi;Yuhong Zhang;Yiming Xu
中科院分区：
文献类型：
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作者：
Meiqing Hu;Y. Wang;Z. Xiong;Dongqin Bi;Yuhong Zhang;Yiming Xu
首次研究了分子碘在可见光（λ≥450 nm）下作为水中2,4,6-三氯苯酚（TCP）降解的增敏剂。在工业I(2)存在的情况下，TCP的降解速率在2 h后显著降低。以磷钨酸（PW）为催化剂，以NaI和h (2)O(2)溶液为碘源，TCP的降解速度快，且符合零级动力学。重要的是，随着时间的推移，I(2)的浓度保持不变，表明I(2)可以作为一种光催化剂回收利用。在TCP降解过程中，产生2,6-二氯-1,4-苯醌作为主要中间体（76%），该中间体在辐照溶液中缓慢降解。在2h时间点，每消耗1等量的TCP，大约产生1.7等量的氯离子。对多金属氧酸盐（POM）类型和各组分初始浓度等变量影响的进一步研究表明，可见光下TCP的降解速率由黑暗中I(2)的生成速率决定。TCP消失的最佳pH为4.5 kJ/mol，表观活化能为42.8 kJ/mol。提出TCP的降解是由I(2)光解产生的碘自由基引发的，然后通过pom催化的H(2)O(2)氧化I(3)（-）来再生I(2)。
Molecular iodine has been studied, for the first time, as a sensitizer for the degradation of 2,4,6-trichlorophenol (TCP) in aqueous solution under visible light (λ ≥ 450 nm). TCP was degraded in the presence of commercial I(2), but the reaction rate decreased significantly after 2 h. When a solution of NaI and H(2)O(2) was used as an iodine source with phosphotungstic acid (PW) as a catalyst, TCP degradation was not only fast but also followed zero-order kinetics. Importantly, the I(2) concentration remained unchanged with time, indicative of I(2) recycling as a kind of photocatalyst. During TCP degradation, 2,6-dichloro-1,4-benzoquinone was produced as the main intermediate (76%), which slowly degraded in the irradiated solution. For every equivalent of TCP consumed at the 2 h time point, approximately 1.7 equivalents of chloride ions were produced. Further study of the effect of variables including the type of polyoxometalates (POM) and the initial concentration of each component revealed that the rate of TCP degradation under visible light was determined by the rate of I(2) production in the dark. The optimum pH and apparent activation energy for TCP disappearance were 4.5 and 42.8 kJ/mol, respectively. It is proposed that TCP degradation is initiated by iodine radicals produced from I(2) photolysis, followed by I(2) regeneration through a POM-catalyzed oxidation of I(3)(-) by H(2)O(2).