摘要
To investigate the effects of salt concentration and freeze-thaw (FT) on the first hydration shell of Zn2+ ions in Zn(NO_3)_2 aqueous solutions, extended X-ray absorption fine structure (EXAFS) spectroscopy was used to examine Zn K-edge EXAFS spectra of Zn(NO_3)_2 aqueous solutions with various concentrations before and after FT treatment. The influences of salt concentration and freeze-thaw on the structural parameters of the first hydration shell of Zn2+ ions, including hydration number, Zn-O distance and thermal disorder, were analyzed. The results show that Zn2+ ions have 3.2―6.8 nearest oxygen neighbors with the Zn-O distance being 0.202―0.207 nm. In highly concen-trated solutions, Zn2+ ions are hydrated with four water molecules in a tetrahedral form. The dilution of Zn(NO_3)_2 aqueous solutions increases the number of water molecules in the first hydration shell of Zn2+ ions to six with their octahedral arrangement. Both the hydration number in the first hydration shell of Zn2+ ions and the degree of thermal disorder increase when the FT treatment is operated in Zn(NO_3)_2 aqueous solutions.
To investigate the effects of salt concentration and freeze-thaw （FT） on the first hydration shell of Zn^2＋ ions in Zn （NO3）2 aqueous solutions, extended X-ray absorption fine structure （EXAFS） spectroscopy was used to examine Zn K-edge EXAFS spectra of Zn （NO3） 2 aqueous solutions with various concentrations before and after FT treatment. The influences of salt concentration and freeze-thaw on the structural parameters of the first hydration shell of Zn^2＋ ions, including hydration number, Zn-O distance and thermal disorder, were analyzed. The results show that Zn^2＋ ions have 3.2--6.8 nearest oxygen neighbors with the Zn-O distance being 0.202--0.207 nm. In highly concentrated solutions, Zn^2＋ ions are hydrated with four water molecules in a tetrahedral form. The dilution of Zn （NO3） 2 aqueous solutions increases the number of water molecules in the first hydration shell of Zn^2＋ ions to six with their octahedral arrangement. Both the hydration number in the first hydration shell of Zn^2＋ ions and the degree of thermal disorder increase when the FT treatment is operated in Zn （NO3） 2 aqueous solutions.
基金
Supported by National Natural Science Foundation of China(No. 20776096)
National Synchrotron Radiation Laboratory, China(No. 20081005G)
