Thallium(I) Oxidation by Permanganate and Chlorine: Kinetics and Manganese Dioxide Catalysis
Thallium(I) Oxidation by Permanganate and Chlorine: Kinetics and Manganese Dioxide Catalysis
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高锰酸盐和氯氧化铊 (I)：动力学和二氧化锰催化
DOI：
10.1021/acs.est.0c00068
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发表时间：
2020
影响因子：
11.4
通讯作者：
Ma Jun
中科院分区：
文献类型：
--
作者：
Zou Yijie;Cheng Haijun;Wang Hainan;Huang Ruixing;Xu Yanghui;Jiang Jin;He Qiang;Liu Caihong;Liu Juchao;Xiong Jiaming;Yao Jinni;Huangfu Xiaoliu;Ma Jun
氧化有毒重金属Tl(I)(Tl(I))是提高水和废水中Tl去除的有效方法。然而，很少有研究关注Tl(I)在水中的氧化动力学，特别是在环境相关的pH值下。因此，本研究对常见试剂KMnO4和HOCl2在环境相关pH条件下氧化Tl(I)的动力学和机理进行了探讨。结果表明，在碱性条件下(pH为8~10)，KMnO_4对Tl(I)的氧化反应为二级动力学，反应的主要活性物种为TlOH，而在pH为4~6的条件下，该反应为自催化反应，且Mn(III)在MnO_2的催化作用中也起重要作用。此外，利用线性自由能关系和X射线光电子能谱(XPS)分析，初步提出了碱性条件下的双电子转移机理。随着pH值的升高，HOCl氧化Tl(I)的反应速率明显降低，质子化氯可能是Tl(I)的主要活性物种。此外，Tl(I)-HOCl反应可视为对Tl(I)的一级反应，但对HOCl的反应级数是可变的。MnO2对HOCl氧化Tl(I)也有明显的催化作用，这主要是由于MnO2上的空位是吸附Tl的活性中心所致。本研究阐明了铊的氧化特性，为除铊过程中的氧化过程奠定了理论基础。
The oxidation of the toxic heavy metal thallium(I) (Tl(I)) is an efficient way to enhance Tl removal from water and wastewater. However, few studies have focused on the kinetics of Tl(I) oxidation in water, especially at environmentally relevant pH values. Therefore, the kinetics and mechanisms of Tl(I) oxidation by the common agents KMnO4and HOCl under environmentally relevant pH condition were explored in the present study. The results indicated that the pH-dependent oxidation of Tl(I) by KMnO4exhibited second-order kinetics under alkaline conditions (pH 8–10) with the main active species being TlOH, while the reaction could be characterized by autocatalysis at pH 4–6, and Mn(III) might also play an essential role in the MnO2catalysis. Furthermore, a two-electron transfer mechanism under alkaline conditions was preliminarily proposed by using linear free energy relationships and X-ray photoelectron spectroscopy (XPS) analysis. Distinctively, the reaction rate of Tl(I) oxidation by HOCl decreased with increasing pH, and protonated chlorine might be the main active species. Moreover, the Tl(I)-HOCl reaction could be regarded as first order with respect to Tl(I), but the order with respect to HOCl was variable. Significant catalysis by MnO2could also be observed in the oxidation of Tl(I) by HOCl, mainly due to the vacancies on MnO2as active sites for sorbing Tl. This study elucidates the oxidation characteristics of thallium and establishes a theoretical foundation for the oxidation processes in thallium removal.