Immobilization of Radioiodine via an Interzeolite Transformation to Iodosodalite

We described a technology for immobilizing radioiodine in the sod-cages by the interzeolite transformation of iodine-containing LTA (zeolite A) and FAU (zeolites X and Y) into a sodalite (SOD) structure. The immobilization of iodine in the sod-cage was confirmed using diverse characterization methods including powder XRD, elemental analysis, SEM–EDS, (127)I MAS NMR, and I 3d XPS. Although both zeolites A (Na-A) and X (Na-X) were well converted into SOD structure in the presence of NaI and AgI, the iodide anions were fixed in the sod-cages only when NaI was used. The ability to adsorb methyl iodide (CH(3)I) was evaluated for zeolites A and X in which Na(+) and/or Ag(+) ions were exchanged, and Ag(+) and zeolite X showed better adsorption properties than Na(+) and zeolite A, respectively. However, when both CH(3)I adsorption ability and the successive immobilization of iodine by interzeolite transformation were considered, Na-X was determined to be the best candidate of adsorbent among the studied zeolites. More than 98% of the iodine was successfully immobilized in the sod-cage in the SOD structure by the interconversion of Na-X following CH(3)I adsorption, although the Na-X zeolite exhibited half the CH(3)I adsorption capacity of Ag-X.