Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, People's Republic of China.
University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
Environ Sci Pollut Res Int. 2022 Jun;29(29):44874-44882. doi: 10.1007/s11356-022-19028-x. Epub 2022 Feb 9.
Iron-bearing clay minerals and arsenic commonly coexist in soils and sediments. Redox oscillation from anoxic to oxic conditions can result in structural Fe(II) oxidation in clay minerals. However, the role of structural Fe(II) oxidation in clay minerals on arsenic immobilization is still unclear. In this study, we found that oxidation of structural Fe(II) in bioreduced clay mineral nontronite (NAu-2) triggered As(III) adsorption onto NAu-2. As(III) was adsorbed onto NAu-2 through ligand exchange with hydroxyl groups which were generated by the oxidation of structural Fe(II) in NAu-2. In addition, oxidation of structural Fe(II) led to the oxidation of As(III) to As(V), which further enhanced the adsorption of dissolved As(III) on NAu-2. Therefore, the adsorption capacity of As(III) onto oxidized NAu-2 was 1.6 times higher than that of native NAu-2. Oxidation of structural Fe(II) was a two-stage process that proceeded from exterior sites to interior sites, and the immobilization and oxidation of As(III) occurred predominantly at the rapid exterior structural Fe(II) oxidation stage. Our findings highlight that the oxidation of structural Fe(II) in iron-bearing clay minerals may play an important role in arsenic immobilization and transformation in the subsurface environment.
含铁粘土矿物和砷通常共存于土壤和沉积物中。缺氧到有氧条件的氧化还原振荡会导致粘土矿物中结构 Fe(II)的氧化。然而，粘土矿物中结构 Fe(II)氧化在砷固定化中的作用仍不清楚。在本研究中，我们发现生物还原的粘土矿物蒙脱石（NAu-2）中结构 Fe(II)的氧化触发了 As(III)吸附到 NAu-2 上。As(III)通过与 NAu-2 中结构 Fe(II)氧化产生的羟基进行配体交换而被吸附到 NAu-2 上。此外，结构 Fe(II)的氧化导致 As(III)氧化为 As(V)，这进一步增强了溶解的 As(III)在 NAu-2 上的吸附。因此，氧化的 NAu-2 对 As(III)的吸附容量比原生 NAu-2 高 1.6 倍。结构 Fe(II)的氧化是一个从外到内的两阶段过程，As(III)的固定和氧化主要发生在快速的外部结构 Fe(II)氧化阶段。我们的研究结果表明，含铁粘土矿物中结构 Fe(II)的氧化可能在地下环境中砷的固定和转化中发挥重要作用。
