Overlooked Role of Chromium(V) and Chromium(IV) in Chromium Redox Reactions of Environmental Importance
Overlooked Role of Chromium(V) and Chromium(IV) in Chromium Redox Reactions of Environmental Importance
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DOI：
10.1021/acsestwater.1c00409
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发表时间：
2022-05
期刊：
影响因子：
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通讯作者：
Joshua Bell;Xingmao Ma;T. McDonald;Ching-Hua Huang;V. Sharma
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文献类型：
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作者：
Joshua Bell;Xingmao Ma;T. McDonald;Ching-Hua Huang;V. Sharma
铬（Cr）是一种众所周知的重金属污染物，其毒性高度依赖于其氧化态。六价铬（Cr(VI)）是一种已知的致癌物，而三价铬（Cr(III)）的毒性要小得多。Cr（VI）的还原和Cr（III）的氧化是通过中间物质五价Cr（Cr(V)）和四价Cr（Cr(IV)）进行的，这两种中间物质具有很强的反应性。环境文献通常缺乏关于各种氧化还原过程中Cr(V)和Cr（IV）种类的信息。本文介绍了Cr(V)和Cr（IV）的水化学性质，包括它们在不同环境条件下的光谱表征和动力学行为。举例说明了在不同的对环境有重要意义的系统中可能存在中间Cr物种，例如铁（II） （Fe(II)）、天然有机物质分子（例如黄腐酸和羧酸）还原Cr(VI)，以及过氧化氢、次氯酸盐和锰氧化物（MnOx）氧化Cr（III）。讨论了Cr(VI) -S （IV）体系对有机污染物的氧化作用。这一观点建议深入研究与环境过程相关的Cr氧化还原反应，以阐明Cr(V)和Cr（IV）物种的产生机制及其在水净化中的作用。
Chromium (Cr) is a well-known heavy metal contaminant with toxicity highly dependent on its oxidation state. Hexavalent Cr (Cr(VI)) is a known carcinogen while trivalent chromium (Cr(III)) is significantly less toxic. The reduction of Cr(VI) and oxidation of Cr(III) in different compartments of the environment occur through intermediate species pentavalent Cr (Cr(V)) and tetravalent Cr (Cr(IV)), which are highly reactive. The environmental literature generally lacks information on Cr(V) and Cr(IV) species in various redox processes. This Perspective presents the aquatic chemistry of Cr(V) and Cr(IV), which includes their spectroscopic characterizations and kinetic behaviors under different environmental conditions. Examples are presented to demonstrate the possible existence of the intermediate Cr species in different systems of environmental importance such as the reduction of Cr(VI) by iron(II) (Fe(II)), molecules of natural organic matter (e.g., fulvic acids and carboxylic acids), and oxidation of Cr(III) by hydrogen peroxide, hypochlorite, and manganese oxides (MnOx). The oxidation of organic pollutants by the Cr(VI)–S(IV) system is also discussed. This Perspective suggests in-depth investigations on the redox reactions of Cr relevant to environmental processes to shed light on the mechanisms of the generation of Cr(V) and Cr(IV) species and their roles in water decontamination.