2023 Fiscal Year Research-status Report
ベントナイトにおけるイオンの拡散の遅滞性に関する実験的検討およびメカニズムの究明
| Project/Area Number |
22K04320
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| Research Institution | Waseda University |
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Principal Investigator |
王 海龍 早稲田大学, 理工学術院, 准教授(任期付) (50822475)
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| Project Period (FY) |
2022-04-01 – 2025-03-31
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| Keywords | basal spacing / bentonite / ion concentration / pore water / salt solutions |
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| Outline of Annual Research Achievements |
This study presents the infiltration behaviors of salt solutions into compacted bentonite with particular examination of the ion concentration in pore water improve understanding on bentonite behaviors in geological disposal project. A Japanese bentonite, Kunigel V1 (K_V1), was used to prepare specimens with 2 mm thickness and the initial dry density of 1.4-1.7 Mg/m3. To each density case, salt solutions (NaCl, KCl and CaCl2) of different solutions (0-2 mol/L) was supplied to the specimens. After infiltration, basal spacing (d001) and exchangeable cations of montmorillonite in the bentonite and leached cations from the bentonite were measured.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In 2023FY, we found that the infiltration capacities of various salt solutions into compacted K_V1 bentonite are in the order of KCl > CaCl2 > NaCl. The K_V1 specimen with higher initial dry density exhibits stronger resistance to salt solution infiltration. After infiltration of NaCl solution into compacted K_V1 bentonite, the increased sodium ions mainly remain in the interparticle pore, leading to an increase in the sodium ion concentration of interparticle pore water. During the infiltration of KCl solution or CaCl2 solution into compacted K_V1 bentonite, the infiltrated potassium or calcium ions tend to enter the interlayer pore preferentially, thereby displacing the exchangeable sodium ions.
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| Strategy for Future Research Activity |
In the last years, mechanism of salt infiltration will be studied in more details by measureing such as basal spacing of montmorillonite, pore water chemistry as well as the application of double diffusive theory to understand the water and salt infiltration process of compacted bentonite.
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