Immobilization of Radioiodine via an Interzeolite Transformation to Iodosodalite.

Hyejin An,Min Bum Park,Jaeyoung Lee,Sanggil Park,Sungjoon Kweon,Hyung-Ki Min

doi:10.3390/nano10112157

Abstract

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, 127I 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 (CH3I) 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 CH3I 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 CH3I adsorption, although the Na-X zeolite exhibited half the CH3I adsorption capacity of Ag-X.

Highlights

In the wake of the Fukushima nuclear power plant disaster in 2011, various radioactive elements were released into the environment, raising the public awareness of their danger
When a severe nuclear accident occurs, radioiodine can be released into the atmosphere in the form of organic iodides like methyl iodide (CH3I), which accounts for the largest proportion of such radioactive iodide compounds
Because they were ccrryystallized under OH- media, these sodalities were HSOD, and their X-ray diffraction (XRD) patterns were in good agreemenntt wwiitthhtthheeliltieterraatuturerereresusultlsts[1[21,21,91,92,72]7.]T. hTehIe/AI/lArlatriaotioof oISfOISDOwDitwhiSthi/ASil/=A1l =wa1swcaa.s0c.3a,. 0b.e3c,abuesceautwseotwioodidode idaneiaonisonfist fiptepr eSrOSDODunuint itceclelll[2[266].].TThhuuss,tthhee iinntteerrzzeeoolliittee transformationn was performed under the conditions of NaI//AAl == 0.3 in the synthesis mixture

Summary

Introduction

In the wake of the Fukushima nuclear power plant disaster in 2011, various radioactive elements were released into the environment, raising the public awareness of their danger. Radioiodine is a well known representative radioactive element. It causes human thyroid cancer, since the thyroid absorbs iodine. The representative radioiodine isotopes are 131I and 129I The former has a short half-life of 8 days and high specific radioactivity. 129I has a relatively long half-life of 1.6 × 107 years and high mobility in most geological environments, which makes it one of the highest dose contributors [1,2]. When a severe nuclear accident occurs, radioiodine can be released into the atmosphere in the form of organic iodides like methyl iodide (CH3I), which accounts for the largest proportion of such radioactive iodide compounds. To selectively remove the highly volatile CH3I contained in the gases released from a nuclear accident, dry filtration systems using adsorbents like zeolites can be effectively used to capture CH3I and immobile it within the adsorbents [3]

Methods

Results

Conclusion