Macroscopic and Microscopic Investigation of Ni(II) Sequestration on Diatomite by Batch, XPS, and EXAFS Techniques
Macroscopic and Microscopic Investigation of Ni(II) Sequestration on Diatomite by Batch, XPS, and EXAFS Techniques
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通过批量、XPS 和 EXAFS 技术对硅藻土上 Ni(II) 封存的宏观和微观研究
DOI：
10.1021/es202108q
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发表时间：
2011-09-15
影响因子：
11.4
通讯作者：
Wang, Xiangke
中科院分区：
文献类型：
--
作者：
Sheng, Guodong;Yang, Shitong;Wang, Xiangke
通过批量、XPS 和 EXAFS 技术研究了硅藻土上 Ni(II) 的封存随时间、pH 和温度的变化。 pH < 7.0 时的离子强度依赖性吸附与外球表面络合一致，而 pH = 7.0-8.6 时的离子强度无关吸附则表明内球表面络合。 EXAFS 结果表明，吸附的 Ni(II) 由类似于 6 O 组成，RNi-O 约为 2.05 埃。第二个壳层的 EXAFS 分析表明，硅藻土/水界面处发生了三种现象：（1）外球和/或内球络合； (2) Si的溶解，这是Ni吸收过程中的限速步骤； (3)表面(共)沉淀物广泛生长。在酸性条件下，外层络合是控制Ni吸收的主要机制，这与宏观结果非常吻合。在接触时间为 1 小时或 1 天或 pH = 7.0-8.0 时，表面共沉淀物与硅藻土表面上的内球复合物同时发生，而在接触时间为 1 个月或 pH = 10.0 时，表面（共）沉淀物主导 Ni 的吸收。此外，表面负载随着温度的升高而增加，并且表面共沉淀成为高温下的主要机制。该结果对于理解固体水界面处镍与矿物质的相互作用具有重要意义，有助于评估自然环境中镍（II）的迁移率。
Sequestration of Ni(II) on diatomite as a function of time, pH, and temperature was investigated by batch, XPS, and EXAFS techniques. The ionic strength-dependent sorption at pH < 7.0 was consistent with outer-sphere surface complexation, while the ionic strength-independent sorption at pH = 7.0-8.6 was indicative of inner-sphere surface complexation. EXAFS results indicated that the adsorbed Ni(II) consisted of similar to 6 O at RNi-O approximate to 2.05 angstrom. EXAFS analysis from the second shell suggested that three phenomena occurred at the diatomite/water interface: (1) outer-sphere and/or inner-sphere complexation; (2) dissolution of Si which is the rate limiting step during Ni uptake; and (3) extensive growth of surface (co)precipitates. Under acidic conditions, outer-sphere complexation is the main mechanism controlling Ni uptake, which is in good agreement with the macroscopic results. At contact time of 1 h or 1 day or pH = 7.0-8.0, surface coprecipitates occur concurrently with inner-sphere complexes on diatomite surface, whereas at contact time of 1 month or pH = 10.0, surface (co)precipitates dominate Ni uptake. Furthermore, surface loading increases with temperature increasing, and surface coprecipitates become the dominant mechanism at elevated temperature. The results are important to understand Ni interaction with minerals at the solid water interface, which is helpful to evaluate the mobility of Ni(II) in the natural environment.