• Duong, Nghia Tuan
• Gottlicher, Jorg
• Steininger, Ralph
• Rasmussen, Camilla Aistrup
• Prevot, Vanessa
• Nielsen, Ulla Gro
• Jensen, Nicholai Daugaard
• Nishiyama, Yusuke
• Bolanz, Ralph

Abstract

<p>The phase purity of a series of ZnAl4(OH)12SO4· nH2O layered double hydroxides (ZnAl4-LDH) obtained from a reaction of bayerite (Al(OH)3) with an excess of zinc(II) sulfate under hydrothermal conditions was investigated as a function of the reaction temperature, the duration of the hydrothermal treatment, and the zinc(II) concentration. The product quality, i.e., crystalline impurities, Al impurities, and bulk Zn:Al ratio, were assessed by powder X-ray diffraction (PXRD),27Al MAS NMR, and elemental analysis. Structural characterization of a stoichiometric ZnAl4-LDH (120 °C, 9 days, and 2.8 M Zn(II)) showed a well-defined structure of the metal ion layer as evidenced by a single, well-defined Zn environment: i.e., no Zn substitution on the Al sites according to Zn k-edge EXAFS and PXRD. Furthermore, nearly all of the 12 different1H atoms in the -OH groups and 427Al resonances could be assigned using1H,27Al NMR correlation experiments recorded with ultrafast MAS. The interlayer water content is variable on the basis of thermogravimetric analysis and changes in the1H MAS NMR spectra with temperature. A composition of ZnAl4(OH)12(SO4)·2.6H2O was obtained from a combination of these techniques and confirmed that ZnAl4-LDH is isostructural with the mineral nickelalumite (NiAl4(OH)12SO4·3H2O).</p>

Topics

• impedance spectroscopy
• mineral
• phase
• experiment
• zinc
• layered
• powder X-ray diffraction
• thermogravimetry
• Nuclear Magnetic Resonance spectroscopy
• elemental analysis
• extended X-ray absorption fine structure spectroscopy