Yan Wei, Wang Liying, Jing Chuanyong
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
J Hazard Mater. 2024 Nov 5;479:135720. doi: 10.1016/j.jhazmat.2024.135720. Epub 2024 Sep 3.
Reactive oxygen species (ROS) production upon the oxygenation of reduced iron minerals is of critical importance to redox cycles of Fe and the fate of refractory organic contaminants. The environmental impact factors during this process, however, have been underappreciated. In this study, prominently enhanced production of hydroxyl radicals (•OH) was observed by oxygenation of Fe(II) with 5-50 mM phosphate. The results of spin trap electron spin resonance (ESR) experiment showed that Fe(II)-phosphate complexes facilitated the generation of •OH. The degradation experiment of p-nitrophenol (PNP) confirmed that •OH formation was dominated by a consecutive one-electron O reduction (90.2-96.9 %), and the quantification of PNP degradation products revealed that Fe(II)/phosphate molar ratios regulated the O activation pathways for O or •OH production. The further experimental and theoretical investigation demonstrated that the coordination of phosphate with Fe(II) plays a dual role in ROS generation that facilitated O formation by lowering the energy barrier for Fe(II) oxidation and altered the reaction pathway of •OH formation due to its occupation of sites for electron transfer. The present work highlights an important role of natural oxyanions in O activation by Fe(II) and raises the possibility of in situ degradation of contaminants in subsurface environment.
还原态铁矿物氧化时活性氧物种（ROS）的产生对于铁的氧化还原循环以及难降解有机污染物的归宿至关重要。然而，这一过程中的环境影响因素一直未得到充分重视。在本研究中，通过用5 - 50 mM磷酸盐氧化Fe(II)，观察到显著增强的羟基自由基（•OH）产生。自旋捕获电子自旋共振（ESR）实验结果表明，Fe(II)-磷酸盐络合物促进了•OH的生成。对硝基苯酚（PNP）的降解实验证实，•OH的形成主要由连续的单电子氧还原主导（90.2 - 96.9%），并且PNP降解产物的定量分析表明，Fe(II)/磷酸盐摩尔比调节了氧或•OH产生的氧活化途径。进一步的实验和理论研究表明，磷酸盐与Fe(II)的配位在ROS生成中起双重作用，通过降低Fe(II)氧化的能垒促进氧的形成，并因其占据电子转移位点而改变了•OH形成的反应途径。本工作突出了天然含氧阴离子在Fe(II)活化氧中的重要作用，并提高了地下环境中污染物原位降解的可能性。
