層状チタン酸塩H_2Ti_3O_7のリチウムイオン交換体としての性質 [in Japanese] Properties of Layered Titanate, H_2Ti_3O_7,as an Inorganic Ion-Exchanger for Lithium [in Japanese]
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Cation exchange properties of layered titanate, H2Ti3O7, were examined in LiOH aqueous solutions of various concentrations. Three phases of exchanged products were observed; L-1 phase having interlayered water, L-2 and L-3 phases having approximate compositions of LixH2-x(Ti3O7) where x=0.8-1.0 and Li2Ti3O7 respectively. These phases could be converted to the original H2Ti3O7 by the treatment in 0.5M HCl solution, i.e. the ion exchange occurred without causing any change in the host (Ti3O7) layer structure. Cation exchange for lithium ions was performed under hydrothermal conditions in the temperature range of 100° to 300°C in an autoclave. The cation exchange for lithium ions was observed up to 190°C but TiO2 (anatase) was additionally formed above 150°C. The contents of TiO2 increased with increasing temperature, and finally the cation exchanged products disappeared at 200°C. H2Ti3O7 acted as an ion-exchanger even after 30 cycles of reversible ion-exchange reactions in 0.2M LiOH aqueous solution and 0.5M HCl solution. Only 0.09% and 0.18% of titanium in H2Ti3O7 eluted into 0.1M and 0.5M HCl solutions at room temperature over a period of 3 days respectively.