Enhancement of ion-exchange properties of highly charged micas by size control of ditrigonal hole

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04640
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 26020:Inorganic materials and properties-related
• Research Institution: Shinshu University
• Principal Investigator: Taruta Seiichi 信州大学, 学術研究院工学系, 教授 (00217209)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 層状化合物 / マイカ / 同形置換 / 結晶構造 / イオン交換

Outline of Final Research Achievements

When Al and Si at the tetrahedral sites of the existing highly-charged Na-4-mica were replaced with larger Ga and Ge respectively, the lattice constants were increased but the ditrigonal holes were reduced. As the ditrigonal holes shrank, the Na+ ions in the interlayers became difficult to enter the ditrigonal holes, and the position and binding state of Na+ ions changed. Along with this, the amount of ion exchange with Sr2+ ions also changed.
A synthesis of novel tetrasilisic-type highly-charged mica was succeeded. When Si at the tetrahedral sites and Li at the octahedral sites were replaced with larger Ge and larger Na respectively, not only mica but also the compounds containing Na were produced. The incorporating of larger Ge and Na expanded not only the lattice constants but also the ditrigonal holes of the producing mica. Na+ ions in the interlayers of the novel highly-charged mica could be exchanged for smaller Li+ ions but were difficult to exchange for larger NH4+ ions.

Free Research Field

無機材料化学

Academic Significance and Societal Importance of the Research Achievements

本研究で、四ケイ素型の新規高電荷密度マイカの合成方法を確立した。大きな理論イオン交換容量を有する新物質の合成という点で学術的・工業的に意義がある。また、既存の高電荷密度Na-4-マイカと新規高電荷密度マイカについて、同形置換による格子定数、六角スペースのサイズおよび層間のNa+イオンの位置と結合状態の変化を解明した。その中で、六角スペースのサイズ、層間イオンの位置と結合状態およびイオン交換能の関連性について、初めて明らかにした。これらの関係から、高電荷密度マイカの実際のイオン交換量を理論陽イオン交換容量まで高めることが可能になれば、有害な金属イオンを効率よく除去できるイオン交換体になり得る。