ISSN:
1432-2021
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
,
Geologie und Paläontologie
,
Physik
Notizen:
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.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00309814
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