Production of reactive oxygen species from oxygenation of Fe(II)-carbonate complexes: The critical roles of carbonate.
Production of reactive oxygen species from oxygenation of Fe(II)-carbonate complexes: The critical roles of carbonate.
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DOI：
10.2139/ssrn.4378242
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发表时间：
2023-04
影响因子：
13.6
通讯作者：
Wen Guo;Wei Yan;C. Jing
中科院分区：
文献类型：
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作者：
Wen Guo;Wei Yan;C. Jing
羟基自由基（·OH）的产生对还原铁矿物在好氧/缺氧界面的氧化已被公认。然而，目前对环境因素的影响及其作用机制还知之甚少。在这项研究中，更多的·OH可以有效地从氧化的Fe（II）与20-200 mM碳酸盐。碳酸盐浓度和缺氧反应时间对·OH的产生起关键作用。高碳酸盐促进Fe（II）高反应性的形成，即，具有低结晶的表面吸附和结构Fe（II），其对用于·OH产生的O2反应具有反应性，而长的缺氧反应时间使得能够从Fe（II）高反应性转移到Fe（II）低反应性，即，Fe（II）在内部位置具有高结晶度，几乎不被O2氧化。对硝基苯酚（PNP）的降解途径与碳酸根浓度密切相关，低浓度碳酸根有利于PNP的·OH氧化（80.2%），而高浓度碳酸根则有利于PNP的O2·-还原（48.7%）。此外，碳酸盐还通过延缓铁矿物的水解和随后的转化，影响铁矿物在氧化过程中的结构演化。我们的发现为理解含氧阴离子（如碳酸根）在铁氧化还原循环中的重要作用以及指导地下环境中污染物的衰减提供了新的思路。
Hydroxyl radicals (•OH) production upon the oxygenation of reduced iron minerals at the oxic/anoxic interface has been well recognized. However, little is known in the influencing environmental factors and the involved mechanisms. In this study, much more •OH could be efficiently produced from oxygenation of Fe(II) with 20-200 mM carbonate. Both carbonate concentration and anoxic reaction time play a critical role in •OH production. High carbonate facilitates the formation of Fe(II)high reactivity, i.e., surface-adsorbed and structural Fe(II) with low crystalline that is reactive toward O2 reaction for •OH production, while long anoxic reaction time enables the transfer from Fe(II)high reactivity to Fe(II)low reactivity, i.e., Fe(II) at interior sites with high crystalline, that is hardly oxidized by O2. Furthermore, the degradation pathway of p-nitrophenol (PNP) is highly dependent on the carbonate concentration that low carbonate facilitates •OH oxidation of PNP (80.2%) while high carbonate enhanced O2•- reduction of PNP (48.7%). Besides, carbonate also influences the structural evolution of Fe mineral during oxygenation by retarding its hydrolysis and following transformation. Our finding sheds new light on understanding the important role of oxyanions such as carbonate in iron redox cycles and directing contaminant attenuation in subsurface environment.