CHANGE IN SORPTION CHARACTERISTICS OF URANIUM DURING CRYSTALLIZATION OF AMORPHOUS IRON MINERALS

Sorption behavior of uranium (VI) during crystallization of amorphous iron (A.Fe) minerals to crystalline iron (C.Fe) minerals have been inv estigated. Two different sorption conditions are applied for the exper iments. One is the condition in which uranium is sorbed on A.Fe minera ls before the crystallization (dynamic condition). The other is the co ndition in which uranium is sorbed on the A.Fe minerals and C.Fe miner als of goethite (static condition). Associations of uranium with the i ron minerals are examined by a selective extraction test using a 1M CH 3COOK solution at pH 7, 1M CH3COONa solution at pH 5 (Morgan's solutio n), and TAO solution (10.9 g.l(-1) oxalic acid+16.1g.l(-1) ammonium ox alate). Under the static condition; the fraction of uranium desorbed b y a 1M CH3COOK solution at pH 7 from A.Fe minerals is lower than that from goethite. And all of uranium are desorbed by the TAO solution fro m both A.Fe minerals and goethite. Contrary, under the dynamic conditi on, fractional uranium is remained after the TAO solution extraction. The fractional uranium remained after the TAO solution extraction from the iron minerals increases with increase in the crystallinity of the iron minerals. The concentrations of uranium in the solutions are les s than Ire. These show that during the crystallization of amorphous to crystalline iron minerals most of uranium associated with the amorpho us iron minerals is not released into the solution, and some fractiona l uranium move to be fixed to crystalline iron minerals.