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

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• 作者：Laure Aimoz ; Christine Taviot-Gu茅ho ; Sergey V. Churakov ; Marina Chukalina ; Rainer D盲hn ; Enzo Curti ; Pierre Bordet ; Marika Vespa
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：March 8, 2012
• 年：2012
• 卷：116
• 期：9
• 页码：5460-5475
• 全文大小：698K
• 年卷期：v.116,no.9(March 8, 2012)
• ISSN：1932-7455

文摘

Uptake of iodine in hydrotalcite-like minerals is a potential retardation mechanism for dose-relevant ¹²⁹I 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鈥揑 and Zn₃Al鈥揑 LDHs was shown generating hexagonal and orthorhombic supercells, respectively. Furthermore, an uncorrelated distribution between I^{鈥?/sup> anions and Zn2+/Al3+ cations was demonstrated, resulting from a dynamic disorder of water and iodide position in the interlayer space.}