PREPARATION AND CHARACTERIZATION OF Fe-, Co-, AND Ni-CONTAINING Mg-Al-LAYERED DOUBLE HYDROXIDES

作     者：Curtius, Hilde Kaiser, Gabriel Rozov, Konstantin Neumann, Andreas Dardenne, Kathy Bosbach, Dirk 

作者机构：Forschungszentrum Julich Inst Energy & Climate Res IEK 6 D-52425 Julich Germany Karlsruhe Inst Technol Inst Nucl Waste Disposal INE D-76344 Eggenstein Leopoldshafen Germany 

出 版 物：《CLAYS AND CLAY MINERALS》 (粘土与粘土矿物)

年 卷 期：2013年第61卷第5期

页      面：424-439页

核心收录：

学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 0708[理学-地球物理学] 0903[农学-农业资源与环境] 0703[理学-化学] 

基　　金：Bundesministerium fur Bildung und Forschung [02E10780] 

主　　题：EXAFS Corrosion Products Layered Double Hydroxides Solubility Thermodynamic Modeling 

摘      要：Syntheses of Fe-, Co-, and Ni-containing Mg-Al-layered double hydroxides (LDHs) are described here because Fe, Co, and Ni represent the major constituents in steel containers used for storing spent nuclear fuel. Much evidence exists for the formation of LDHs during the corrosion of such containers under repository-relevant conditions. Because of their anion-exchange properties, LDHs can be considered as materials with the potential to retain and immobilize anionic radionuclides. Evaluation of the thermodynamic properties of LDHs is essential for reliable prediction of their behavior (solubility, anion exchange properties) in geochemical environments. The impact on the thermodynamic properties of the isostructural incorporation of divalent cations into the LDH was the main focus of the present study. Mg-Al-Cl-LDH and the Fe-, Co-, and Ni-doped LDHs were synthesized by the co-precipitation method and then characterized (using powder X-ray diffraction (PXRD), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDX), and thermogravimetric analyses (TGA)). The PXRD and EXAFS analyses indicated that all synthesized samples were pure LDHs where Co, Ni, and Fe were incorporated isostructurally. The EXAFS and XANES results demonstrated that Ni and Co were incorporated as divalent cations and Fe as a trivalent cation. Thermodynamic calculations were performed assuming an equilibrium state between aqueous solutions and corresponding precipitates after synthesis. The first estimates of the molar Gibbs free energies for Fe-, Co-, and Ni-containing LDHs at 70 degrees C were provided. The calculated Gibbs free energy of the pure Mg-Al-LDH (-3629 kJ/mol) was slightly less than those for Fe-, Co-, and Ni-containing compositions (-3612 +/- 50, -3604 +/- 50, -3593 +/- 50 kJ/mol).