Ion-exchange reaction with inorganic compounds was attempted to prepare new compounds and to adsorb anion or rare earth metal ions in solution. The Li
+ ion in LiTaWO
6 with the trirutile-type structure was ion-exchanged completely with proton to yield HTaWO
6·nH
2O. The protonated compounds, HTaWO
6·nH
2O had high selectivity for incorporation of Li
+ ion and was strong brønsted acid. The Rb
+ ion in Rb
8Nb
22O
59 with a tunnel structure was ion-exchanged with proton and Na
+ ion, and the Cs
+ ion in Cs
3Fe
0.5Nb
5.5O
16 with a tunnel structure was replaced partially with Rb
+ ion by immersing in molten salt. The pyrolysis products of Y
2(OH)
6−x(NO
3)
x·nH
2O exhibited good performance of adsorption for Cl
− ion in acidic solution. 13 inorganic compounds were attempted to adsorb rare earth metal ions in solution, and both of γ-ZrP and HAp had high ability for adsorption of rare earth metals in solution.
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