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Fukushima-shi, Japan

Morodome S.,Tokyo Institute of Technology | Morodome S.,Kunimine Industries Co. | Kawamura K.,Tokyo Institute of Technology | Kawamura K.,Okayama University
Clays and Clay Minerals | Year: 2011

The swelling property of smectite is dominated by the hydration of exchangeable cations in the interlayer spacing ('interlayer hydration'). By investigating systematically the swelling behavior of various exchangeable cations with different valences and ionic radii, the interlayer hydration of smectite was explored. The swelling behavior of Li +-, K +-, Rb +-, Cs +-, Mg 2+-, Sr 2+-, Ba 2+-, and La 3+- montmorillonites in undersaturated conditions was measured precisely over the range 50-150°C by in situ X-ray diffraction (XRD) analyses. The systematic swelling behavior of ten homocationic montmorillonites, the aforementioned eight homoionic montmorillonites, plus Na + and Ca 2+ froma previous study, and the cation hydration energies were analysed by studying the changes occurring in the basal spacing and the 001 peak width. With decreasing cation hydration energy, swelling curves (i.e. plots of basal spacing vs. relative humidity (RH)) change from continuous (Mg 2+, La 3+, and Ca 2+) to stepwise (Sr 2+, Li +, Ba 2+, and Na +) to one-layer only (K +, Rb +, and Cs +). For the first two groups, the RH at the midpoint between the one- and two-layer hydration states increased as the cation hydration energy decreased. Under low RH, with increasing temperature, the basal spacings of Mg-, La-, Ca-, Sr-, Li-, and Ba-montmorillonites decreased continuously to the zero-layer hydration state, whereas Na-, K-, Rb-, and Cs-montmorillonites swelled from the zero-layer hydration state even at the lowest temperature (50°C). A decrease in the basal spacing at the same RH but at different temperatures suggests the existence of metastable states or that the layer-stacking structure changes with temperature. The systematics of the swelling behavior of various homocationic montmorillonites as functions of RH and temperature (<150°C) at 1 atmare reported here.

Ito H.,Kunimine Industries Co. | Miyasaka N.,Hokkaido University | Kozaki T.,Hokkaido University | Sato S.,Hokkaido University
Journal of Nuclear Science and Technology | Year: 2010

Hydraulic conductivities were determined for compacted Fe(III)- montmorillonite sample. The Fe(III)- montmorillonite sample used in this study, which was prepared by the ion-exchange treatment of Na- montmorillonite in FeCl 3 solution, contains less than 20% of Na+ ions as exchangeable cations and negligibly small amounts of iron precipitates. The measured hydraulic conductivities of compacted Fe(III)-montmorillonite were determined to be the order of 10-9, 10-11, and 10-13 ms-1 at dry densities of 0.80, 1.01, and 1.20 Mgm-3, respectively. These values were found to be kept constant during the experimental period, suggesting no significant change in the physicochemical properties of Fe(III)- montmorillonite during the experiment. When compared with Na-montmorillonite, remarkably high values of hydraulic conductivities were found for Fe(III)-montmorillonite at the dry densities of 0.8 and 1.0 Mgm-3. On the other hand, almost the same value of hydraulic conductivity was obtained at the dry density around 1.2 Mgm-3. This different effect of exchangeable cations on the hydraulic conductivity of montmorillonite could be attributed to the different sizes of macropores in compacted montmorillonite and/or the different thicknesses of electrical double layers formed over montmorillonite sheets. ©Atomic Energy Society of Japan.

Fukushi K.,Kanazawa University | Sugiura T.,Kanazawa University | Morishita T.,Kanazawa University | Takahashi Y.,Hiroshima University | And 2 more authors.
Applied Geochemistry | Year: 2010

Greenish veins occurring in brecciated bentonite were found in the Kawasaki bentonite deposit of the Zao region in Miyagi Prefecture, Japan. Their occurrence possibly indicates the interaction of bentonite with Fe-rich hydrothermal solutions. In order to prove the hypothesis and understand the long-term mineralogical and petrographic evolution of bentonite during such interactions, the greenish veins and the surrounding altered bentonite were analyzed using X-ray fluorescence (XRF), scanning electron microscopy (SEM), X-ray diffraction (XRD), electron probe micro-analysis (EPMA), scanning transmission electron microscopy with energy dispersed spectroscopy (STEM-EDS) and micro X-ray absorption near-edge structure (XANES). The greenish veins resulting from hydrothermal solution are composed of mixed-layer minerals consisting of smectite and glauconite (glaucony), pyrite and opal. The occurrences indicate that glaucony and pyrite formed almost simultaneously from hydrothermal solution prior to opal precipitation. The mineral assemblages of the greenish veins and their surroundings indicate that the hydrothermal activity had most likely taken place at a temperature of less than 100°C and that the pH and Eh conditions of the reacted solution were neutral to alkaline pH and reducing. The unaltered bentonite is composed mainly of Al smectite and opal. These minerals coexist as a mixture within the resolution level of the microprobe analyses. On the other hand, the bentonite in contact with the greenish veins consists of discrete opal grains and dioctahedral Al smectite containing Fe and was altered mineralogically and petrographically by the hydrothermal activity. Both the clay minerals and the opal were formed by dissolution and subsequent precipitation from the interaction of the original bentonite with the hydrothermal solution.Because of the similarity of the alteration conditions to those in the geological disposal environment, it was considered that the occurrence of Fe-bentonite interactions in the Kawasaki bentonite deposit could yield valuable input for predicting bentonite stability under disposal conditions. © 2010 Elsevier Ltd.

Kimura H.,Gifu University | Ueno M.,Gifu University | Takahashi S.,Gifu University | Tsuchida A.,Gifu University | Kurosaka K.,Kunimine Industries Co.
Applied Clay Science | Year: 2014

The electrically induced viscosity change of a deionized hectorite aqueous dispersion under an alternating current (AC) electric field was investigated. The hectorite dispersion showed a reversible viscosity change when an AC electric field (<. ca. 0.01. Hz) of the order of a few V/mm was applied and removed thereafter, although it showed an incomplete reversibility when a direct current (DC) electric field was applied. Regarding the mechanism of reversible viscosity change, it can be considered that the hectorite is well dispersed as individual layers or as small flocs without an electric field. These form a three-dimensional network structure, which returns to the original dispersion state upon removal of the alternating electric field. © 2014 Elsevier B.V.

Kimura H.,Gifu University | Nakashima A.,Gifu University | Takahashi S.,Gifu University | Tsuchida A.,Gifu University | Kurosaka K.,Kunimine Industries Co.
Applied Clay Science | Year: 2015

A change in the viscosity of a deionized stevensite aqueous dispersion under an electric field of the order of a few V/mm was recently discovered. The dispersion shows a reversible change of viscosity with the application and removal of an AC electric field. Regarding the mechanism of the reversible viscosity change, it can be considered that the by applying an electric field, the stevensite forms some flocs and a weak network structure, which leads to the increased viscosity, while it returns to a well-dispersed state and its original viscosity by removing the electric field. The viscosity response of the stevensite dispersion for an AC electric field was faster than that of the hectorite dispersion in the same measuring condition. It is speculated that the quick viscosity change would be related to the unique charge distribution on the stevensite, which is known to form a finer network structure than hectorite, beyond a critical concentration of salt. This finding offers great potential for controlling the dispersion state and sedimentation/floatation velocity, by an electric field, of various colloidal particles dispersed in the clay mineral dispersions. © 2015 Elsevier B.V.

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