Development of Ion Memorized Materials by Using Ion-Exchange Reactions

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The technique of the compositional modification by using ion exchange reactions can produce metastable materials with various unique characteristics. In this study, we have synthesized the ion memorized materials by means of the ion exchange, especially K^+ and Br^- ions memorized materials which selectively take up K^+ and Br^- ions in the presence of a large excess of analogous ins, and then have investigated the characteristics on the metastable materials. Consequently ,the outstanding ion selectivity was discovered on modified fluormicas and apaties.1. Two modified fluormicas(NaT and HT)were prepared by substituting Na^+ and H^+ ions for interlayer K^+ ions in taeniolites [KMg_2LiSi_4O_<10>F_2]. The cation exchange selectivities for Na^+, K^+, Mg^<2+>, and Ca^<2+> ions on NaT and HT have been examined. The orders of cation selectivities on NaT and HT were found to be K^+>>Mg^<2+>*Ca^<2+>>Na^+,and NaT and HT took up a regular amount of K^+ ions without depending on the concentrations of Na^+, Mg^<2+>, and Ca^<2+> ions, which coexisted in aqueous solution. From the results, it was concluded that NaT and HT were K^+ ion memorized ion exchanger, and could be utilized in the separation and immobilization of K^+ ions from the system including Na^+, K^+, Mg^<2+>, and Ca^<2+> ions, for example, seawater, body fluid, and so on.2. A modified apatite(PbBr_<2-x>Cl_xAp)was prepared by substituting Br^- for Cl^- ions in lead bromapatite [PbBrAp;Pb_<10>(PO_4)_6Br_2]. The anion exchange selectivities for Br^- ions in the presence of Cl^- ions on PbBr_<2-x>Cl_xAp and PbClAp have been examined. PbBr_<2-x>Cl_xAp selectively took up Br^- ions in spite of depending on the concentration of Br^- ions, while PbClAp scarcely took up Br^- ions. The results suggested that PbBr_<2-x>Cl_xAp exhibited the Br^- ion memorized characteristics, and was useful for the separation and immobilization of Br^- ions.