Abiotic reduction of nitroaromatic compounds by aqueous iron(ll)-catechol complexes.
Abiotic reduction of nitroaromatic compounds by aqueous iron(ll)-catechol complexes.
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DOI：
10.1021/es060044t
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发表时间：
2006-03
影响因子：
11.4
通讯作者：
Daisuke Naka;Dongwook Kim;T. Strathmann
中科院分区：
文献类型：
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作者：
Daisuke Naka;Dongwook Kim;T. Strathmann
儿茶酚和硫醇配体与铁(l)的络合形成了能够将取代的硝基芳香族化合物（NACs）还原为相应的苯胺的水溶液。在纯feli或纯配体溶液中未观察到NACs的反应。在含有FeII和铁（一种模型儿茶酚）的溶液中，NAC的还原速率严重依赖于pH、配体浓度和离子强度。观察到的4-氯硝基苯还原的伪一级速率常数（k(obs)）变化超过6个数量级，这种变异性可以用表达式k(obs) = k(FeL2)(6-) [FeL2(6-)]很好地描述，其中[FeL2(6-)]是1:2的fei -铁络合物的浓度，kFeL2（6-）是4-氯硝基苯与该物质反应的双分子速率常数。FeII的高反应活性是由于FeIII/FeII氧化还原对的标准单电子还原电位较低（EH0 = -0.509 V vs NHE）。不同nac的相对反应活性可以用nac的单电子还原势EH1′（ArNO2）与线性自由能关系来描述。实验推导出的LFER斜率表明电子转移是速率决定的。这些发现表明，非有机配合物可能在持久性有机污染物的还原转化中起着重要的作用，这是以前未被认识到的。
Complexation of iron(ll) by catechol and thiol ligands leads to the formation of aqueous species that are capable of reducing substituted nitroaromatic compounds (NACs) to the corresponding anilines. No reactions of NACs are observed in FelI-only or ligand-only solutions. In solutions containing FeII and tiron, a model catechol, rates of NAC reduction are heavily dependent on pH, ligand concentration, and ionic strength. Observed pseudo-first-order rate constants (k(obs)) for 4-chloronitrobenzene reduction vary by more than 6 orders of magnitude, and the variability is well described by the expression k(obs) = k(FeL2)(6-) [FeL2(6-)], where [FeL2(6-)] is the concentration of the 1:2 FeII-tiron complex and kFeL2(6-) is the bimolecular rate constant for 4-chloronitrobenzene reaction with this species. The high reactivity of this FeII species is attributed to the low standard one-electron reduction potential of the corresponding FeIII/FeII redox couple (EH0 = -0.509 V vs NHE). The relative reactivity of different NACs can be described by a linear free-energy relationship (LFER) with the one-electron reduction potentials of the NACs, EH1'(ArNO2). The experimentally derived slope of the LFER indicates that electron transfer is rate determining. These findings suggest that FeII-organic complexes may play an important, previously unrecognized, role in the reductive transformation of persistent organic contaminants.