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Solubility and Thermodynamic Properties of Carbonate-Bearing Hydrotalcite—Pyroaurite Solid Solutions with A 3:1 Mg/(Al+Fe) Mole Ratio
- K. B. Rozov, U. Berner, D. A. Kulik, L. W. Diamond
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- Journal:
- Clays and Clay Minerals / Volume 59 / Issue 3 / June 2011
- Published online by Cambridge University Press:
- 01 January 2024, pp. 215-232
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- Article
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The naturally occurring layered double hydroxides (LDH, or anionic clays) are of particular interest in environmental geochemistry because of their ability to retain hazardous cations and especially anions. However, incorporation of these minerals into predictive models of water-rock interaction in contaminant environments, including radioactive-waste repositories, is hampered by a lack of thermodynamic and stability data. To fill part of this gap the present authors have derived properties of one of the complex multicomponent solid solutions within the LDH family: the hydrotalcite-pyroaurite series, Mg3(Al1−xFex)(OH)8(CO3)0.5·2.5H2O.
Members of the hydrotalcite-pyroaurite series with fixed MgII/(AlIII+FeIII) = 3 and various FeIII/(FeIII+AlIII) ratios were synthesized by co-precipitation and dissolved in long-term experiments at 23±2°C and pH = 11.40±0.03. The chemical compositions of co-existing solid and aqueous phases were determined by inductively coupled plasma-optical emission spectroscopy, thermogravimetric analysis, and liquid scintillation counting of 55Fe tracers; X-ray diffraction and Raman were used to characterize the solids. Based on good evidence for reversible equilibrium in the experiments, the thermodynamic properties of the solid solution were examined using total-scale Lippmann solubility products, ΣΠT. No significant difference was observed between values of SPT from co-precipitation and from dissolution experiments throughout the whole range of Fe/Al ratios. A simple ideal solid-solution model with similar end-member ΣΠT values (a regular model with 0 < WG < 2 kJ mol −1 sufficient to describe the full range of intermediate mineral compositions. In turn, this yielded the first estimate of the standard Gibbs free energy of the pyroaurite end member, G298,Pyro = −3882.60±2.00 kJ/mol, consistent with G298,Htlco = −4339.85 kJ/mol of the hydrotalcite end member, and with the whole range of solubilities of the mixed phases. The molar volumes of the solid-solution at standard conditions were derived from X-ray data. Finally, Helgeson’s method was used to extend the estimates of standard molar entropy and heat capacity of the end members over the pressure-temperature range 0−70°C and 1–100 bar.
EURECA – The Future of Cryogenic Dark Matter Detection in Europe
- E. Pécontal, T. Buchert, Ph. Di Stefano, Y. Copin, H. Kraus, E. Armengaud, M. Bauer, I. Bavykina, A. Benoit, A. Bento, J. Blümer, L. Bornschein, A. Broniatowski, G. Burghart, P. Camus, A. Chantelauze, M. Chapellier, G. Chardin, C. Ciemniak, C. Coppi, N. Coron, O. Crauste, F.A. Danevich, M. De Jésus, P. de Marcillac, E. Daw, X. Defay, G. Deuter, J. Domange, P. Di Stefano, G. Drexlin, L. Dumoulin, K. Eitel, F. von Feilitzsch, D. Filosofov, P. Gandit, E. Garcia, J. Gascon, G. Gerbier, J. Gironnet, H. Godfrin, S. Grohmann, M. Gros, M. Hannewald, D. Hauff, F. Haug, S. Henry, P. Huff, J. Imber, S. Ingleby, C. Isaila, J. Jochum, A. Juillard, M. Kiefer, M. Kimmerle, H. Kluck, V.V. Kobychev, V. Kozlov, V.M. Kudovbenko, V.A. Kudryavtsev, T. Lachenmaier, J.-C. Lanfranchi, R.F. Lang, P. Loaiza, A. Lubashevsky, M. Malek, S. Marnieros, R. McGowan, V. Mikhailik, A. Monfardini, X.-F. Navick, T. Niinikoski, A.S. Nikolaiko, L. Oberauer, E. Olivieri, Y. Ortigoza, E. Pantic, P. Pari, B. Paul, G. Perinic, F. Petricca, S. Pfister, C. Pobes, D.V. Poda, R.B. Podviyanuk, O.G. Polischuk, W. Potzel, F. Pröbst, J. Puimedon, M. Robinson, S. Roth, K. Rottler, S. Rozov, C. Sailer, A. Salinas, V. Sanglard, M.L. Sarsa, K. Schäffner, S. Scholl, S. Scorza, A. Smolnikov, W. Seidel, S. Semikh, M. Stern, L. Stodolsky, M. Teshima, V. Tomasello, A. Torrento, L. Torres, V.I. Tretyak, J.A. Villar, M.A. Verdier, I. Usherov, J. Wolf, E. Yakushev
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- Journal:
- European Astronomical Society Publications Series / Volume 36 / 2009
- Published online by Cambridge University Press:
- 30 May 2009, pp. 249-255
- Print publication:
- 2009
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EURECA (European Underground Rare Event Calorimeter Array) is an astro-particle physics facility aiming to directly detect galactic dark matter. The Laboratoire Souterrain de Modane has been selected as host laboratory. The EURECA collaboration unites CRESST, EDELWEISS and the Spanish-French experiment ROSEBUD, thus concentrating and focussing effort on cryogenic detector research in Europe into a single facility. EURECA will use a target mass of up to one ton, enough to explore WIMP – nucleon scalar scattering cross sections in the region of 10-9 – 10-10 picobarn. A major advantage of EURECA is the planned use of more than just one target material (multi target experiment for WIMP identification).