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首页> 外文期刊>Environmental Science & Technology >Polyoxometalate-Enhanced Oxidation of Organic Compounds by Nanopaiticulate Zero-Valent Iron and Ferrous Ion in the Presence of Oxygen
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Polyoxometalate-Enhanced Oxidation of Organic Compounds by Nanopaiticulate Zero-Valent Iron and Ferrous Ion in the Presence of Oxygen

机译：氧存在下纳米微粒化零价铁和亚铁离子对多金属氧酸盐增强有机化合物的氧化

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摘要

In the presence of oxygen, organic compounds can be oxidized by zerovalent iron or dissolved Fe(II). However, this process is not a very effective means of degrading contaminants because the yields of oxidants are usually low (i.e., typically less than 5% of the iron added is converted into oxidants capable of transforming organic compounds). The addition of polyoxometalate (POM) greatly increases the yield of oxidants in both systems. The mechanism of POM enhancement depends on the solution pH. Under acidic conditions, POM mediates the electron transfer from nanoparticulate zerovalent iron (nZVI) or Fe(II) to oxygen, increasing the production of hydrogen peroxide, which is subsequently converted to hydroxyl radical through the Fenton reaction. At neutral pH values, iron forms a complex with POM, preventing iron precipitation on the nZVI surface and in bulk solution. At pH 7, the yield of oxidant approaches the theoretical maximum in the nZVI/O_2 and the Fe(II)/O_2 systems when POM is present, suggesting that coordination of iron by POM alters the mechanism of the Fenton reaction by converting the active oxidant from ferryl ion to hydroxyl radical. Comparable enhancements in oxidant yields are also observed when nZVI or Fe(II) is exposed to oxygen in the presence of silica-immobilized POM.
机译：在氧气存在下，有机化合物可以被零价铁或溶解的Fe（II）氧化。但是，该方法不是降解污染物的非常有效的方法，因为氧化剂的收率通常较低（即，通常少于5％的添加的铁被转化为能够转化有机化合物的氧化剂）。在两个系统中添加多金属氧酸盐（POM）均可大大提高氧化剂的收率。 POM增强的机制取决于溶液的pH值。在酸性条件下，POM介导电子从纳米零价铁（nZVI）或Fe（II）转移到氧气，从而增加了过氧化氢的产生，随后通过Fenton反应将其转化为羟基自由基。在中性pH值下，铁与POM形成络合物，从而防止铁在nZVI表面和本体溶液中沉淀。在pH值为7时，当存在POM时，在nZVI / O_2和Fe（II）/ O_2系统中，氧化剂的产率接近理论最大值，这表明通过POM配位铁可通过转换活性氧化剂来改变Fenton反应的机理。从亚铁离子到羟基自由基当nZVI或Fe（II）在二氧化硅固定的POM存在下暴露于氧气时，也观察到氧化剂产量的相对提高。

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