Solidification of Iodide Ion by Reaction with Bi2O3

Abstract α-Bi2O3 is a candidate material for the immobilization of radioactive iodine. The present paper discusses a method for removing radioactive iodide ion by fixing it into α-Bi5IO7 by a direct reaction with α-Bi2O3; it also reports on experimental conditions under which aqueous iodide reacts with α-Bi2O3 to form a single phase of α-Bi5IO7. α-Bi2O3 was reacted with aqueous iodide in LiI, NaI, KI, and NH4I solutions. Although a previous paper reported that the concentration of aqueous iodide ion was the most important factor to form a single phase of α-Bi5IO7, the present result shows that it is not an important factor. The α-Bi5IO7 single phase can be obtained regardless of the concentration of iodide ion when the ratio of the gram molecular number of the bismuth oxide and the gram ion number of the radioactive iodide ion is adjusted in the range 5 : 2 to 1 : 2 in a LiI solution, 4 : 1 to 1 : 2 in a NaI solution, and 4 : 1 to 1 : 4 in a KI solution. A reaction in a NH4I solution does not produce a single phase of Bi5IO7 at any ratio.