The coprecipitation of uranium with calcium carbonate

This report is one of the studies on the factors controlling the trace element contents of marine calcareous skeletons. The values of the distribution coefficients of UO₂ ²⁺ between solutions and carbonate precipitates were measured in the laboratory at 20±1C. From the determination of the uranium contents of marine calcareous skeletons and sea water, the values of uranium between marine calcareous skeletons and sea water are expected as 1.2 to 0.3 for aragonite and 0.2 to 0,0n for calcite. The experimentally measured value of the distribution coefficient for aragonite is thermodynamically discussed. And it was known that the value of the distribution coefficient of UO₂ ²⁺ is controlled greatly by the activity coefficient of uranium dissolved in a parent medium and the crystal form of CaCO₃. The activity coefficient of uranium in solution mainly owes to the formation of complexes between UO₂ ²⁺ and CO₃ ^2–in the solution.