Oxidation kinetics of anilines by aqueous permanganate and effects of manganese products: Comparison to phenols.
Oxidation kinetics of anilines by aqueous permanganate and effects of manganese products: Comparison to phenols.
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DOI：
10.1016/j.chemosphere.2019.06.156
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发表时间：
2019-11
期刊：
影响因子：
8.8
通讯作者：
Su-yan Pang;Jie-bin Duan;Yang Zhou;Yuan Gao;Jin Jiang
中科院分区：
文献类型：
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作者：
Su-yan Pang;Jie-bin Duan;Yang Zhou;Yuan Gao;Jin Jiang
本研究首先系统研究了高锰酸钾（Mn(VII)）对苯胺消除的潜在适用性，重点研究了锰中间体对苯胺对苯酚动力学的影响。结果表明，Mn（VII）能较好地氧化苯胺，苯胺的二阶速率常数kMn（VII）随pH值从5增加到9而减小。文献中提出的动力学模型成功地描述了这种有趣的ph依赖性，以解释酚的不寻常的ph速率分布，其中Mn（VII）和酚或苯胺之间的中间体的形成可能涉及。研究了锰产物mno2和Mn（III）对Mn（VII）氧化苯胺的影响。在微酸性条件下，Mn（VII）与苯胺的反应表现出自催化作用，表明原位生成的mno2与苯酚具有相似的催化作用。在酸性pH下，几种配体（如焦磷酸盐）抑制了mno2胶体的形成，降低了Mn（VII）对苯胺的氧化速率，而在类似条件下，这些配体大大加速了苯酚的动力学。配体的不同作用可能主要是由于原位形成的配体稳定的Mn（III）对苯胺和酚的反应活性不同。腐植酸的复杂作用高度依赖于溶液pH，这可能是由于腐植酸的双重作用，它可以作为还原剂（竞争性消耗Mn（VII）和苯氧基或苯胺自由基）以及配体（稳定锰中间体如Mn(III)）来影响Mn（VII）反应。
In this study, the potential applicability of potassium permanganate (Mn(VII)) for anilines elimination was systematically investigated firstly, with a focus on the effect of manganese intermediates on the kinetics of anilines versus phenols. It was found that Mn(VII) could fairly oxidize anilines, where the second-order rate constants (kMn(VII)) values for anilines always decreased as pH increased from 5 to 9. This interesting pH-dependency was successfully described by the kinetic models proposed in literature to account for the unusual pH-rate profiles for phenols, where the formation of intermediates between Mn(VII) and phenols or anilines was likely involved. The effect of manganese products such as MnO2and Mn(III) on the oxidation of anilines by Mn(VII) was demonstrated. Under slightly acidic conditions, the reactions of Mn(VII) with anilines displayed autocatalysis, suggesting a similar catalytic role of MnO2formed in situ as compared to phenols. Several ligands (e.g., pyrophosphate) inhibited the formation of MnO2colloids and lowered the oxidation rates of anilines by Mn(VII) at acidic pH, while these ligands greatly accelerated the kinetics of phenols under similar conditions. The contrasting effects of ligands might be mainly attributed to the different reactivity of ligand-stabilized Mn(III) formed in situ toward anilines vs phenols. The complex effect of humic acid was highly dependent on solution pH, possible due to the dual role of humic acid that it could act as a reductant (competitively consuming Mn(VII) and phenoxy or aniline radical) as well as a ligand (stabilizing manganese intermediates such as Mn(III) species) to affect Mn(VII) reactions.