Anion and Cation Order in Iodide-Bearing Mg/Zn-Al Layered Double Hydroxides

作者：Aimoz Laure^*; Taviot Gueho Christine; Churakov Sergey V; Chukalina Marina; Daehn Rainer; Curti Enzo; Bordet Pierre; Vespa Marika

来源：Journal of Physical Chemistry C, 2012, 116(9): 5460-5475.

DOI：10.1021/jp2119636

Uptake of iodine in hydrotalcite-like minerals is a potential retardation mechanism for dose-relevant I-129 in the near-field of a deep repository for radioactive waste. The location of iodide in (Zn/Mg)Al layered double hydroxides (LDH) was investigated using a combination of advanced atomic-scale techniques. Wavelet transform analysis of Zn K-edge extended X-ray absorption fine structure (EXAFS) spectra and geometry optimization based on ab initio density functional calculations allowed the distribution of Al3+ in the cationic layer to be determined. Using Rietveld refinement of synchrotron X-ray powder diffraction data (XRD) and EXAFS at the I K-edge enabled the average location of iodide in the interlayer to be established. Additional short- and medium-range structural information was also obtained from the pair distribution function analysis of the XRD data in support of the findings obtained with the long- and short-range techniques. By combining the results, a local order of Al3+ in Zn2Al-I and Zn3Al-I LDHs was shown generating hexagonal and orthorhombic supercells, respectively. Furthermore, an uncorrelated distribution between I- anions and Zn2+/Al3+ cations was demonstrated, resulting from a dynamic disorder of water and iodide position in the interlayer space.

• 出版日期2012-3-8