期刊
DALTON TRANSACTIONS
卷 40, 期 41, 页码 10953-10960出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c1dt10740b
关键词
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资金
- National Natural Science Foundation of China [20907055, 20971126]
- MOST of China [2007CB936602, 2011CB933700]
- Anhui Province Technology Fund for Outstanding Youths [10040606Y34]
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(NO3)(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 (RNi-Al = 3.00 angstrom, RNi-Si1 = 3.10 angstrom and RNi-Si2 = 3.26 angstrom) 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 (RNi-Ni = 3.07 angstrom and RNi-Si = 3.26 angstrom) 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.
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