Hydrotalcite-like solid solutions with variable SO
4
2?
and CO
3
2?
contents at 50° C |
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| Authors: | Carole Le Bail Jean-Hugues Thomassin Jean-Claude Touray |
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| Institution: | 1. Laboratoire de Métallogénie et Géochimie Minérale, école Supérieure de l'Energie et des Matériaux, Université d'Orléans, 45067, Orléans cedex 2, France
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| Abstract: | Hydrotalcite-like solid solutions have been synthesized by coprecipitation in basic solutions with variable SO 4 2? /CO 3 2? ratios. Chemical determination of CO 3 2? in the interlayer was impossible because of the presence of minor hydromagnesite. SO 4 2? was determined both by chemical analysis and X-ray photoelectron spectroscopy (XPS), the two methods giving similar results. A Raman spectrometry gave additional data on the SO 4 2? /CO 3 2? ratio. Then, the stoichiometry of the anionic interlayers, X s , X c , and X OH were determined, and the influence of X s on the c′ parameter (increasing from c′=7.97 Å to c′=8.63 Å between X s =0 and X s =1) was characterized. In addition, a partitioning curve of SO 4 2? and CO 3 2? between aqueous solutions and hydrotalcite-like compounds was established. Its general shape strongly suggests a miscibility gap between a sulfate-rich end and a carbonate-rich solid solution (maximum SO 4 2? /CO 3 2? about 0.2). This result explains why most of the hydrotalcites synthesized during experimental alteration of basaltic glasses by sea-water (a sulfate-rich solution) are CO 3 2? -rich solid solutions. |
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