Surface Sorption Site and Complexation Structure of Ca2 at the Goethite-Water Interface: A Molecular Dynamics Simulation and Quantitative XANES Analysis
Surface Sorption Site and Complexation Structure of Ca2 at the Goethite-Water Interface: A Molecular Dynamics Simulation and Quantitative XANES Analysis
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针铁矿-水界面处 Ca2 的表面吸附位点和络合结构：分子动力学模拟和 XANES 定量分析
DOI：
10.1007/s00128-019-02641-x
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发表时间：
2019
影响因子：
2.7
通讯作者：
Wang Shaofeng
中科院分区：
文献类型：
--
作者：
Jia Yongfeng;Zheng Yang;Lin Jinru;Zhang Guoqing;Ma Xu;Wang Xin;Wang Shaofeng
Ca2+在针铁矿/水界面的分子水平表面络合结构仍不清楚。我们使用经典分子动力学 (MD) 模拟和 CaK 边缘 X 射线吸收近边缘结构 (XANES) 光谱研究了针铁矿表面上 Ca2+ 的吸附。 XANES 结果表明，在 pH≤≤9 时，Ca2+ 主要通过吸附被针铁矿螯合，而 Ca(OH)2 表面沉淀在 pH 10 时形成，初始 Ca2+ 浓度为 2 mM。 MD模拟表明，Ca2+主要通过双齿双核络合作用吸附在针铁矿的（100）和（110）表面上，形成≡（Fe-OH）2Ca2+·5H2O物质，而少量Ca2+吸附在（021）表面上。理论 CaK 边缘 XANES 光谱计算得出针铁矿/水界面处的平均 Ca-O 原子间距离为 2.34 Å (2.23–2.55 Å)，Ca-Fe 原子间距离为 3.80 Å (3.79–3.81 Å)。我们的结果可能有助于了解钙和其他相关阳离子和阴离子的地球化学循环。
The molecular-level surface complexation structure of Ca2+at the goethite/water interface remains unclear. We investigated the sorption of Ca2+on the surfaces of goethite using classical molecular dynamics (MD) simulations and CaK-edge X-ray absorption near edge structure (XANES) spectroscopy. The XANES results showed that Ca2+was sequestered by goethite dominantly via sorption at pH ≤ 9, whereas the Ca(OH)2surface precipitate formed at pH 10 for an initial Ca2+concentration of 2 mM. The MD simulations showed that Ca2+dominantly absorbed on the (100) and (110) surfaces of goethite via bidentate binuclear complexation by forming ≡(Fe-OH)2Ca2+·5H2O species, whereas little Ca2+adsorbed on the (021) surface. The theoretical CaK-edge XANES spectrum calculations gave a mean Ca-O interatomic distance of 2.34 Å (2.23–2.55 Å) and a Ca-Fe interatomic distance of 3.80 Å (3.79–3.81 Å) at goethite/water interface. Our results may shed some light on the geochemical cycling of calcium and other related cations and anions.