Characterization of homoionic Fe-type montmorillonite; Potential chemical species of iron contaminant

Kozai, Naofumi   ; Inada, Koichi*; Adachi, Yoshifusa*; Kawamura, Sachi*; Kashimoto, Yusuke*; Kozaki, Tamotsu*; Sato, Seichi*; Onuki, Toshihiko; Sakai, Takuro; Sato, Takahiro; Oikawa, Masakazu*; Esaka, Fumitaka  ; Mitamura, Hisayoshi

Fe-montmorillonite with Fe ions occupying cation exchange sites is an ideal transformation product in bentonite buffer material. We previously prepared a Fe-montmorillonite sample using a FeCl solution under an inert gas condition. This study attempted to determine the potential contaminant iron chemical species in the sample. It was found that a small amount of Cl ions remained dispersed throughout the sample. The Cl ion retention may be due to the adsorption of FeCl in the initial FeCl solution and the subsequent containment of the Cl ions that are dissociated from the FeCl during excess salt removal treatment. The latter may be explained by the slow release of the remaining Cl ions from the collapsed interlayer of the montmorillonite or the transformation of a minor fraction of the remaining FeCl to iron (III) hydroxide chloride complexes having low solubility.