浓度及冷冻-解冻处理对CuCl_2水溶液中Cu~(2+)区域结构的影响

应用扩展X射线吸收精细结构(EXAFS)光谱研究了CuCl2水溶液中Cu2+的区域环境结构,通过测定CuCl2水溶液在不同浓度条件下及冷冻-解冻(FT)处理前后CuK边EXAFS吸收谱,研究了浓度及冷冻-解冻处理对Cu2+第一配位层结构的影响.EXAFS实验结果表明,CuCl2水溶液中Cu2+第一配位层距离中心原子Cu最近邻原子为O原子,配位数介于3.0-4.3之间,Cu—O键长在0.192-0.198nm之间,这种结构与Cu2+的Jahn-Teller效应有关.不同浓度的CuCl2水溶液中Cu2+的区域环境结构有很大不同,随着CuCl2水溶液浓度的升高,Cu2+第一配位层配位数减小,Cu—O键伸长.结构参数拟合结果证实冷冻-解冻处理对Cu2+的区域环境结构有影响,CuCl2溶液经冷冻-解冻处理后,Cu2+第一配位层配位数变大,热无序度增加.

Effects of Concentration and Freeze-Thaw Treatment on the Local Structure of Cu~(2+) in CuCl_2 Aqueous Solutions

The microscopic local environmental structure of Cu~(2+) ions in copper chloride solutions was investigated by X-ray absorption free structure (EXAFS) spectroscopy. The effects of salt concentration and freeze-thaw (FT) treatment on the first coordination shell of Cu~(2+) were analyzed by examining the Cu K edge EXAFS spectra of CuCl_2 aqueous solutions before and after FT treatment at various concentrations. The EXAFS results show that Cu~(2+) has 3.0-4.3 oxygen nearest neighbors with Cu-O bond length of 0.192-0.198 nm in the first coordination shell. These structural properties can be ascribed to the Jahn-Teller effect. We found differences in the microscopic local structure of Cu~(2+) for various concentrations in CuCl_2 aqueous solutions. With an increase in the salt concentration, the coordination number of Cu~(2+) decreases and the Cu-O bond length increases in the first coordination shell. The influence of FT treatment on the microscopic local environmental structure of Cu~(2+) was determined firm the fitting results of the structural parameters. The coordination number of Cu~(2+) in its first coordination shell and the degree of thermal disorder increase when the FT treatment is operated in CuCl_2 aqueous solutions.