期刊
DALTON TRANSACTIONS
卷 41, 期 35, 页码 10803-10810出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c2dt31057k
关键词
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资金
- 973 project from MOST of China [2011CB933700]
- National Natural Science Foundation of China [20907055, 20971126, 21077107, 21107115]
- Anhui Province Technology Fund for Outstanding Youths [10040606Y34]
The influence of humic acid (HA) on Ni(II) sorption to Ca-montmorillonite was examined by using a combination of batch sorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The sorption of Ni(II) on HA-montmorillonite hybrids is strongly dependent on pH and temperature. At low pH, the sorption of Ni(II) is mainly dominated by Ni-HA-montmorillonite and outer-sphere surface complexation. The EXAFS results indicate that the first coordination shell of Ni(II) consists of similar to 6 O atoms at the interatomic distances of similar to 2.04 angstrom in an octahedral structure. At high pH, binary Ni-montmorillonite surface complexation is the dominant sorption mechanism. EXAFS analysis indicates the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5, while a Ni-Al layered double hydroxide (LDH) phase at the Ca-montmorillonite surface formed with pH 8.5. At pH 10.0, the dissolved HA-Ni(II) complexation inhibits the precipitation of Ni hydroxide, and Ni-Al LDH phase forms. The rise of temperature increases the sorption capacity of Ni(II), and promotes Ni-Al LDH phase formation and the growth of crystallites. The results are important to evaluate the physicochemical behavior of Ni(II) in the natural environment.
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