Thermal and radiolytic resistance of AR-01R anion exchanger containing Benzimidazole groups as exchange sites in nitric acid solution has been studied. Changes in its exchange capacity (EC), structure and shape were investigated and compared with those of a commercial Amberlite IRA-900 anion exchanger with quaternary ammonium group. Compared to the IRA-900, the AR-01R anion exchanger showed significantly higher thermal resistance and its decrease in EC was less than 10% after immersion in 9 mol⋅dm^-3 HNO₃ solution for 72 h. On the other hand, it was found that the EC decrease of these two anion exchangers induced by γ-ray irradiation was almost the same; their EC decreased by 20-25% after irradiation in 9 mol⋅dm^-3 HNO₃ solution at room temperature with absorption dose of 3.0 MGy. The change of the strong-base benzimidazole group to weak-base benzimidazole group in AR-01 was found to be the main damage by heat and γ-ray irradiation.

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The structure, synthesis, and ion-sieve properties of porous manganese oxide crystals were reviewed. Tunnel and layered manganese oxides constitute a large family of porous materials having pore size in the region from ultramicropores to micropores. They can be prepared by using various metal ions as templates. The template ions are extracted topotactically from the tunnels or interlayer spaces of the manganese oxides by two different mechanisms: redox and ion-exchange. These manganese oxide show excellent ion-sieve properties for the adsorption of metal ions; the adsorptive selectivities are dependent on their structures.

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The ion exchange reactions are classified as the topochemical reaction or the host-guest reaction in which neither the bond formation nor the bond breaking occurs. The unique property of such reaction is that the free energy change is rather small in contrast to the ordinary chemical reaction as well as that neither the guest molecule nor the host compound suffers from chemical change. In such reactions, the small free energy change causes the large selectivity change. Various factors have been known to affect the ion exchange selectivity. Among them, the dehydration reaction of ions of interest on occasion of ion exchange is considered to be superior factor. The dehydration degree is generally larger in the inorganic ion exchangers than the organic resins. Correspondingly, the selectivity is also larger in the inorganic ion exchangers. The correlation between the ion exchange selectivity and the hydration property are discussed in several examples including ⁷Li/⁶Li isotope separation reaction in which the free energy change is extremely small.

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