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Title: Stabilization of Co{sup 2+} in layered double hydroxides (LDHs) by microwave-assisted ageing

Abstract

Co-containing layered double hydroxides at different pH have been prepared, and aged following different routes. The solids prepared have been characterized by element chemical analysis, powder X-ray diffraction, thermogravimetric and differential thermal analyses (both in nitrogen and in oxygen), FT-IR and Vis-UV spectroscopies, temperature-programmed reduction and surface area assessment by nitrogen adsorption at -196 deg. C. The best conditions found to preserve the cobalt species in the divalent oxidation state are preparing the samples at controlled pH, and then submit them to ageing under microwave irradiation. - Graphical abstract: The use of microwave-hydrothermal treatment, controlling both temperature and ageing time, permits to synthesize well-crystallized nanomaterials with controlled surface properties. An enhancement in the crystallinity degree and an increase in the particle size are observed when the irradiation time is prolonged.

Authors:
 [1];  [1];  [1];  [2]
  1. Departamento de Quimica Inorganica, Universidad de Salamanca, Salamanca-37008 (Spain)
  2. Departamento de Quimica Inorganica, Universidad de Salamanca, Salamanca-37008 (Spain), E-mail: vrives@usal.es
Publication Date:
OSTI Identifier:
21015724
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 3; Other Information: DOI: 10.1016/j.jssc.2006.12.011; PII: S0022-4596(06)00648-7; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AGING; COBALT; DIFFERENTIAL THERMAL ANALYSIS; FOURIER TRANSFORMATION; HYDROXIDES; INFRARED SPECTRA; IRRADIATION; MICROWAVE RADIATION; NANOSTRUCTURES; NITROGEN; OXYGEN; PARTICLE SIZE; PHYSICAL RADIATION EFFECTS; SPECTROSCOPY; SURFACE AREA; TEMPERATURE RANGE 0065-0273 K; THERMAL GRAVIMETRIC ANALYSIS; X-RAY DIFFRACTION

Citation Formats

Herrero, M., Benito, P., Labajos, F.M., and Rives, V.. Stabilization of Co{sup 2+} in layered double hydroxides (LDHs) by microwave-assisted ageing. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2006.12.011.
Herrero, M., Benito, P., Labajos, F.M., & Rives, V.. Stabilization of Co{sup 2+} in layered double hydroxides (LDHs) by microwave-assisted ageing. United States. doi:10.1016/j.jssc.2006.12.011.
Herrero, M., Benito, P., Labajos, F.M., and Rives, V.. Thu . "Stabilization of Co{sup 2+} in layered double hydroxides (LDHs) by microwave-assisted ageing". United States. doi:10.1016/j.jssc.2006.12.011.
@article{osti_21015724,
title = {Stabilization of Co{sup 2+} in layered double hydroxides (LDHs) by microwave-assisted ageing},
author = {Herrero, M. and Benito, P. and Labajos, F.M. and Rives, V.},
abstractNote = {Co-containing layered double hydroxides at different pH have been prepared, and aged following different routes. The solids prepared have been characterized by element chemical analysis, powder X-ray diffraction, thermogravimetric and differential thermal analyses (both in nitrogen and in oxygen), FT-IR and Vis-UV spectroscopies, temperature-programmed reduction and surface area assessment by nitrogen adsorption at -196 deg. C. The best conditions found to preserve the cobalt species in the divalent oxidation state are preparing the samples at controlled pH, and then submit them to ageing under microwave irradiation. - Graphical abstract: The use of microwave-hydrothermal treatment, controlling both temperature and ageing time, permits to synthesize well-crystallized nanomaterials with controlled surface properties. An enhancement in the crystallinity degree and an increase in the particle size are observed when the irradiation time is prolonged.},
doi = {10.1016/j.jssc.2006.12.011},
journal = {Journal of Solid State Chemistry},
number = 3,
volume = 180,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Ni containing layered double hydroxides (LDHs) have been prepared by precipitation and hydrothermally treated under microwave irradiation for different periods of time. The solids have been calcined at three temperatures corresponding to stable phases formed during thermal decomposition of LDHs. The properties of the irradiated samples and of the calcined products were studied in order to ascertain whether the ageing treatment under microwave irradiation modifies not only the properties of the layered materials, but also the properties of the calcined products. A structural and textural study was carried out by PXRD, FT-IR and Vis-UV spectroscopy, thermal analyses (DTA and TG),more » N{sub 2} adsorption/desorption at -196 {sup o}C and TEM microscopy; the reducibility of the nickel species was studied as well by TPR. The results show that the microwave treatment leads to better crystallized LDHs with modified thermal stability and reducibility. In addition, the degree of crystallinity of the layered precursors and their textural properties determine the properties of their thermal decomposition products. - Graphical abstract: Layered double hydroxides were prepared by the microwave-hydrothermal treatment. This method allows obtaining in short periods of time well crystallized LDHs with well-defined hexagonal-shaped particles, and improved thermal stability and the textural properties. In addition, the degree of crystallinity of the layered precursors and their textural properties determine the properties of t thermal decomposition products.« less
  • Layered double hydroxides (LDHs) have shown great promise as anion getters. In this paper, we demonstrate that the sorption capability of a LDH for a specific oxyanion can be greatly increased by appropriately manipulating material composition and structure. A large set of LDH materials have been synthesized with various combinations of metal cations, interlayer anions, and the molar ratios of divalent cation M(II) to trivalent cation M(III). The synthesized materials have then been tested systematically for their sorption capabilities for pertechnetate (TcO{sub 4}{sup -}). It is discovered that for a given interlayer anion (either CO{sub 3}{sup 2-} or NO{sub 3}{supmore » -}) the Ni-Al LDH with a Ni/Al ratio of 3:1 exhibits the highest sorption capability among all the materials tested. The distribution coefficient (K{sub d}) is determined to be as high as 307 mL/g for Ni{sub 6}Al{sub 2}(0H){sub 16}CO{sub 3}nH{sub 2}O and 1390 mL/g for Ni{sub 6}Al{sub 2}(OH){sub 16}NO{sub 3}nH{sub 2}O at a pH of 8. The sorption of TcO{sub 4}{sup -} on M(II)-M(III)-CO{sub 3} LDHs is dominated by the edge sites of LDH layers and strongly correlated with the basal spacing d{sub 003} of the materials, which increases with the decreasing radii of both divalent and trivalent cations. The sorption reaches its maximum when the layer spacing is just large enough for a pertechnetate anion to fit into a cage space between two neighboring octahedra of metal hydroxides at the edge. Furthermore, the sorption is found to increase with the crystallinity of the materials. For a given combination of metal cations and an interlayer anion, a best crystalline LDH material is obtained generally with a M(II)/M(III) ratio of 3:1. Replacement of interlayer carbonate with readily exchangeable nitrate greatly increases the sorption capability of a LDH material for pertechnetate, due to the enhanced adsorption on edge sites and the possible contribution from interlayer anion exchanges. The work reported here will help to establish a general structure-property relationship for the related layered materials.« less
  • No abstract prepared.
  • Layered double hydroxides (LDHs) are anionic clays important in disciplines such as environmental chemistry, geochemistry, and materials science. Developments in signal processing of extended X-ray absorption fine structure (EXAFS) data, such as wavelet transformation (WT), have been used to identify transition metals and Al present in the hydroxide sheets of LDHs. The WT plots of LDHs should be distinct from those of isostructural single metal hydroxides. However, no direct comparison of these minerals appears in the literature using WT. This work systematically analyzes a suite of Ni-rich mineral standards, including Ni–Al LDHs, single metal Ni hydroxides, and Ni-rich silicates usingmore » WT. The results illustrate that the WT plots for α-Ni(OH)2 and Ni–Al LDHs are often indistinguishable from each other, with similar two-component plots for the different mineral types. This demonstrates that the WT of the first metal shell often cannot be used to differentiate an LDH from a single metal hydroxide. Interlayer anions adsorbed to the hydroxide sheet of α-Ni(OH)2 affect the EXAFS spectra and are not visible in the FT but are clearly resolved and discrete in the WT.« less
  • The layered double hydroxides (LDHs) of Mg with Ga and In decompose completely on heating to 500 deg. C to yield poorly ordered oxide residues. In the Mg-Ga system, the oxide residue has a rock-salt structure with Ga incorporated in the MgO matrix. In the Mg-In system, the oxide residue is X-ray amorphous. These oxide residues revert back to the original LDH either on standing in a water-saturated atmosphere or on hydrothermal treatment in a Na{sub 2}CO{sub 3} solution. In contrast, the LDHs of Co with Ga and In yield the thermodynamically stable spinel oxides and the decomposition is irreversible.more » These results have implications for the synthesis of 'oxide' catalysts by thermal decomposition of the LDHs.« less