Sorption speciation of nickel(II) onto Ca-montmorillonite: batch, EXAFS techniques and modeling.
Sorption speciation of nickel(II) onto Ca-montmorillonite: batch, EXAFS techniques and modeling.
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DOI：
10.1039/c1dt10740b
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发表时间：
2011-10
影响因子：
4
通讯作者：
X. Tan;Jun Hu;G. Montavon;Xiangke Wang
中科院分区：
文献类型：
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作者：
X. Tan;Jun Hu;G. Montavon;Xiangke Wang
镍（II）的吸附形态的钙蒙脱石进行了评价，使用组合的批实验，扩展X射线吸收精细结构（EXAFS）光谱和建模。在水-蒙脱石界面的pH值和温度影响的程度，Ni（II）的吸附，以及吸附的Ni（II）离子的局部原子结构。在0.001molL（-1）Ca（NO3）（2）和低pH条件下，Ni（Ⅱ）主要吸附在Ca-蒙脱石层间，并与八面体中的6个水分子配位形成外层络合物。在较高的pH值下，形成内球表面复合物。由EXAFS测定的Ni-Si/Al距离（R（Ni-Al）= 3.00 μ m，R（Ni-Si 1）= 3.10 μ m和R（Ni-Si 2）= 3.26 μ m）证实了在pH 7.5和8.5时位于Ca-蒙脱石片晶边缘的单核复合物的形成。在pH 10.0时，Ni-Ni/Si距离（R（Ni-Ni）= 3.07 μ m，R（Ni-Si）= 3.26 μ m）表明形成了Ni层状硅酸盐沉淀。温度的升高促进内球络合，这反过来又导致增加Ni（II）吸附在钙蒙脱石。吸附边缘拟合良好的表面络合模型（SCM）的援助，从EXAFS光谱确定的表面物种。
The sorption speciation of Ni(II) on Ca-montmorillonite was evaluated using a combination of batch experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy and modeling. The pH and temperature at the aqueous-montmorillonite interface affects both the extent of Ni(II) sorption as well as the local atomic structure of the adsorbed Ni(II) ions. At 0.001 mol L(-1) Ca(NO(3))(2) and low pH, the study reveals that the majority of Ni(II) is adsorbed in the interlayers of Ca-montmorillonite coordinated by six water molecules in an octahedron as an outer-sphere complex. At higher pH, inner-sphere surface complexes are formed. The Ni-Si/Al distances (R(Ni-Al) = 3.00 Å, R(Ni-Si1) = 3.10 Å and R(Ni-Si2) = 3.26 Å) determined by EXAFS confirm the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5 and 8.5. At pH 10.0, the Ni-Ni/Si distances (R(Ni-Ni) = 3.07 Å and R(Ni-Si) = 3.26 Å) indicates the formation of Ni-phyllosilicate precipitates. A rise in temperature promotes inner-sphere complexation, which in turn leads to an increase in Ni(II) sorption on Ca-montmorillonite. Sorption edges are fitted excellently by surface complexation model (SCM) with the aid of surface species determined from EXAFS spectroscopy.