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

概要

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Calcium sulfate hemihydrate was synthesized in NaCl-solutions to determine the apparent partition coefficient of strontium (D_<sr>) 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 D_<sr> (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.
日本地球化学会の論文
1987-12-10