Iodine K-Edge Exafs Spectroscopy of Iodine-Bearing AFm-(Cl2, CO3, SO4)

Extended X-ray absorption fine structure (EXAFS) spectroscopy at the iodine K-edge was performed to investigate the immobilization of iodide by AFm-Cl

2

/CO

3

/SO

4

phases. AFm-I

2

and various compositions of AFm-(I

2

, Cl

2

), AFm-(I

2

, CO

3

), and AFm-(I

2

, SO

4

) were synthesized by coprecipitation and exchange reaction. X-ray diffraction (XRD) showed that AFm-(I

2

, Cl

2

) sample crystallize in two separate crystalline phases AFm-I

2

and AFm-Cl

2

. This finding was supported by EXAFS measurements, which showed that the coordination environment of iodine is similar for AFm-(I

2

, Cl

2

) and pure AFm-I

2

. AFm-(I

2

, CO

3

) interlayers alternately filled with I

−

and with (OH

−

–CO

3

2−

) were observed by XRD, whereas a more limited short-range ordering of iodide was found by EXAFS spectroscopy. XRD indicated that AFm-(I

2

, SO

4

) forms a solid solution between AFm-I

2

and AFm-SO

4

. In addition, the EXAFS spectra revealed that I

−

and SO

4

2−

occupy neighbouring positions. The formation of an AFm-I

2

–AFm-SO

4

solid solution together with the complete mixing of I

−

and SO

4

2−

confirms the capability of AFm-SO

4

to trap

129

I.