Incorporation of strontium into calcium sulfate hemihydrates

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Other Title
  • 硫酸カルシウム1/2水和物へのストロンチウムの取り組み
  • 硫酸カルシウム1/2水和物へのストロンチウムの取り込み
  • リュウサン カルシウム 1 2 スイワブツ ヘ ノ ストロンチウム ノ トリコ

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Abstract

Calcium sulfate hemihydrate was synthesized in NaCl-solutions to determine the apparent partition coefficient of strontium (Dsr) between the hemihydrate and its solution. Hemihydrate containing about 5% sodium ions (Na-hemihydrate ) precipitated from NaCl-saturated solution at temperatures between 64℃ and 95℃. If the temperature was below 64℃, gypsum (Na-free) formed in the solution, while anhydrite (Na-free) was found above 95℃. Crystal water was more stable in Na-hemihydrate against heating than in Na-free hemihydrates. This may be due to hydrogen bonds in Na-hemihydrate. Na-hemihydrate had the largest value of Dsr (2.1 to 2.5) among calcium sulfate polymorphs. Substitution of one calcium ion by two sodium ions may make more lattice sites available for strontium ions. Na-free hemihydrates were unstable in Na-free solutions when the temperature was below 100℃. Bassanite (hemihydrate mineral), however, does exist in evaporative environments such as continental sabkha zone pans. A high salt concentration may stabilize the mineral in these environments.

Journal

  • Chikyukagaku

    Chikyukagaku 21 (2), 55-64, 1987

    The Geochemical Society of Japan

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