Hydrothermal experiments using Fe-bentonite; Identification of change of Fe-bentonite under low oxygen and high temperature conditions

Suyama, Tadahiro*; Shibata, Masahiro ; Sasamoto, Hiroshi   

In previous experiment, we studied about interaction bentonite and Fe by the laboratory experiment that bentonite mixed with iron powder was kept for 6 years at room temperature in the glove box (O 1 ppm). It was shown that bentonite was not influenced about its property, but change to Fe-bentonite. In this experiment, it is aimed to confirm mineralogical change of start substance, which is Fe-bentonite changed from Na-bentonite beforehand, by accelerating reactions on high temperature. Fe-bentonite was prepared by mixing Na-bentonite (Kunipia F) and FeCl solution in the glove box (Ar, O 1 ppm). Fe-bentonite samples were put into Au-tubes, and they were kept at 250C in autoclave for 1 month and 6 months. 6 months sample was confirmed the peak of a iron-containing 7AA non-expandable clay mineral (i.e. berthierin). For the confirmation of reversibility of ion-exchange, 6 months sample was mixed with 1M-NaCl solution. XRD analysis for the treated sample under humidity controlled condition showed a same result with that of Na-bentonite. This means that a change of the sample was only ion-exchange reaction in the bentonite inter-layer, and bentonite properties was not changed.