Anoxic storage regenerates reactive Fe(II) in reduced nontronite with short-term oxidation
Anoxic storage regenerates reactive Fe(II) in reduced nontronite with short-term oxidation
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缺氧储存可通过短期氧化在还原绿脱石中再生活性 Fe(II)
DOI：
10.1016/j.gca.2019.04.027
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发表时间：
2019-07
影响因子：
5
通讯作者：
Man Tong
中科院分区：
文献类型：
--
作者：
Wenjuan Liao;Songhu Yuan;Xixiang Liu;Man Tong
含 Fe(II) 的粘土矿物代表氧化还原动力系统下的大型电子源。尽管含 Fe(II) 的粘土矿物与氧化剂（如 O2）之间的氧化还原反应已在氧化还原动力系统中得到广泛研究，但尚未探索的一个重要过程是粘土矿物中 Fe(II) 反应性对短期氧化后长期缺氧储存的响应。在这里，我们使用还原绿脱石NAu-2作为模型含铁粘土矿物，将其悬浮液暴露在空气中短时间（1、3和5小时）氧化，然后在缺氧条件下长时间（0-120小时）储存，不添加任何外源氧化剂。经过不同时间的缺氧储存后，我们通过空气氧化评估了 Fe(II) 的反应性，通过磷酸盐萃取测量了 Fe(II) 分数，并通过 X 射线光电子能谱 (XPS)、傅里叶变换红外光谱 (FTIR) 和穆斯堡尔谱表征了 Fe(II) 的变化。我们发现缺氧储存显着增加了Fe(II)被O2氧化的速率以及由此产生的羟基自由基的产生，并且对于缺氧储存时间较长的NAu-2，这种增加更为明显。磷酸盐提取和XPS结果均表明，与边缘位点相关的活性Fe(II)得到了再生，并且再生率随着缺氧储存时间的增加而增加。 FTIR 和穆斯堡尔谱鉴定了缺氧储存期间 NAu-2 结构的重排。缺氧储存反应性 Fe(II) 再生的机制归因于与边缘位点相关的反应性 Fe(II) 的增加，这很可能是由绿脱石八面体片中从内部位点的 Fe(II) 到边缘位点的 Fe(III) 的电子转移引起的。由于不同的 Fe(II)/Fe(III) 比率，电子转移的驱动力被认为是边缘和内部位点之间的氧化还原电位梯度。我们的研究结果提高了对 Fe(II)/Fe(III) 相互转化的理解，以及由此减少氧化还原动力系统下含 Fe(II) 的粘土矿物引起的物质转化的影响。
Fe(II)-bearing clay minerals represent a large electron source under redox-dynamic systems. Although redox reactions between Fe(II)-bearing clay minerals and oxidants (such as O2) have been widely investigated in redox-dynamic systems, one important process that remains unexplored is the response of Fe(II) reactivity in clay minerals to long-term anoxic storage following short-term oxidation. Here we used reduced nontronite NAu-2 as a model Fe-bearing clay mineral, exposed its suspension to air for oxidation in a short time (1, 3 and 5 h), and then stored it under anoxic conditions without any exogenous oxidants for a long time (0–120 h). After different time of anoxic storage, we evaluated the reactivity of Fe(II) by air oxidation, measured the Fe(II) fractions by phosphate extraction and characterized the variation of Fe(II) by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Mössbauer. We found that anoxic storage increased prominently the rate of Fe(II) oxidation by O2and the resultant production of hydroxyl radicals, and the increase was more obvious for the NAu-2 with a longer time of anoxic storage. Both phosphate extraction and XPS results revealed that the reactive Fe(II) associated with edge sites was regenerated and the regeneration increased with the increase in anoxic storage time. FTIR and Mössbauer spectra identified the rearrangements of NAu-2 structure during anoxic storage. The mechanism of reactive Fe(II) regeneration by anoxic storage was attributed to the increase in reactive Fe(II) associated with edge sites, which was most likely induced by the electron transfer from Fe(II) at the interior sites to Fe(III) at the edge sites in the octahedral sheets of nontronite. The driving force for electron transfer was presumed to be the redox potential gradient between edge and interior sites because of different Fe(II)/Fe(III) ratios. Our findings improve the understanding of Fe(II)/Fe(III) interconversion as well as the resultant reducing impact on substance transformation induced by Fe(II)-bearing clay minerals under redox-dynamic systems.
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DOI：
10.1021/bk-2011-1071.ch017
发表时间：
2011
期刊：
--
影响因子：
--
作者：
A. Neumann;M. Sander;T. Hofstetter
通讯作者：
A. Neumann;M. Sander;T. Hofstetter
影响因子：
5
作者：
A. Neumann;S. Petit;T. Hofstetter
通讯作者：
A. Neumann;S. Petit;T. Hofstetter
影响因子：
3.7
作者：
V. Alexandrov;K. Rosso
通讯作者：
V. Alexandrov;K. Rosso
影响因子：
5
作者：
S. Welch;B. Beard;C. Johnson;P. S. Braterman
通讯作者：
S. Welch;B. Beard;C. Johnson;P. S. Braterman
影响因子：
12.8
作者：
Liu, Xixiang;Yuan, Songhu;Liu, Deng
通讯作者：
Liu, Deng