Reactive halogen radicals in saline water promote photochemically-assisted formation of manganese oxide nanosheets
Reactive halogen radicals in saline water promote photochemically-assisted formation of manganese oxide nanosheets
复制标题
盐水中的反应性卤素自由基促进光化学辅助氧化锰纳米片的形成
DOI：
10.1039/d2en00410k
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Jun, Young-Shin
中科院分区：
文献类型：
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作者：
Gao, Zhenwei;Skurie, Charlie;Jun, Young-Shin
在海洋和河口，卤素离子天然丰富。从海水淡化过程和非常规石油和天然气开采过程中产生大量高盐度外流并排放到地表水中。这些高浓度的卤化物会产生活性卤素自由基。然而，卤素自由基与重金属或过渡金属的氧化还原反应很少受到关注。在这里，我们报道了活性卤素自由基对锰离子(Mn2+)的快速氧化。羟基自由基(·OH)是由硝酸盐光解产生的。在Mn2+的直接氧化过程中，·OH自由基的作用有限，而·OH自由基可与卤离子反应生成活性卤素自由基，从而氧化Mn2+。此外，1 mM溴−产生的溴(Br2+)自由基对Mn2+的氧化作用大于5 0 0mM Cl−产生的氯(Cl)自由基。在Br2+的存在下，Mn2+的非生物氧化速率大大提高，反应6h内Mn2+(AQ)的氧化速率提高了62%。这项研究加深了我们对自然Mn2+氧化过程的理解，并突出了活性卤素自由基对重金属氧化还原活性的意外影响以及相应的卤水中纳米级固体矿物的形成。这项工作提供了一种新的、环境友好的、简便的合成MnO2纳米片的方法。
Halide ions are naturally abundant in oceans and estuaries. Large amounts of highly saline efflux are also made and discharged to surface water from desalination processes and from unconventional oil and gas recovery. These highly concentrated halides can generate reactive halogen radicals. However, the redox reactions of halogen radicals with heavy metals or transition metals have received little attention. Here, we report undiscovered fast oxidation of manganese ions (Mn2+) by reactive halogen radicals. Hydroxyl radicals (˙OH) are produced by nitrate photolysis. While ˙OH radicals play a limited role in the direct oxidation of Mn2+, ˙OH can react with halide ions to generate reactive halogen radicals to oxidize Mn2+. In addition, more Mn2+ was oxidized by bromide (Br) radicals generated from 1 mM Br− than by chloride (Cl) radicals generated from 500 mM Cl−. In the presence of Br radicals, the abiotic oxidation rate of Mn2+ to Mn(IV)O2 nanosheets is greatly promoted, showing a 62% increase in Mn2+(aq) oxidation within 6 h of reaction. This study advances our understanding of natural Mn2+ oxidation processes and highlights unexpected impacts of reactive halogen radicals on redox activities with heavy metals and corresponding nanoscale solid mineral formation in brine. This work suggests a new, environmentally-friendly, and facile pathway for synthesizing MnO2 nanosheets.