Ion-exchange-type extractants showed lithium isotopic fractionations in the solvent extraction reaction, depending on their ion selectivity. The extractants having high Na⁺ selectivity, calix [4] arene derivative and monensin, showed high lithium isotope separation factors of 1.030 and 1.022, respectively.

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Although studies on charged membranes have been widely spreading, most of ion exchange membranes, which are a typical charged membrane, are used in ion transport through the membranes in the presence of electrical potential. In some cases, transport number of counter ions should increase and new additional functions were required for the membranes. A typical example of the former is to increase current efficiency of the membranes for chlor-alkali process at the initial stage of development and one of the latter is to give permselectivity for specific ions to the membranes. In particular, many studies on providing permselectivity for specific ions to the membranes have been made in both cation and anion exchange membranes, e. g., in cation exchange membranes, to form a cationic charged layer on the membrane surface, to introduce phosphonic acid groups as ion exchange groups in the membrane and to electrodialyze mixed salt solution in the presence of chelate-forming agents; in anion exchange membranes, to form an anionic charged layer on the membrane surface and to control balance between hydrophilicity of the anion exchange membrane and hydration energy of anions. These works are summarized in this paper.

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Ion exchange resins are frequently used for water treatment, with the type of technology being of critical importance. Bayer has recently succeeded in producing the latest generation of monodisperse resins characterized by improved chemical and physical properties. This paper deals with the advantages of this completely new ion exchange resins over heterodisperse types.

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The paper describes haw to clarify ion exchange mechanisms by experiments of stoichiometry, pH titration curve and ion exchange ideality of uni-, di-, and trivalent metal ions on the exchangers. Determination of ion exchange capacity is demonstrated including breakthrough experiment. In order to more understand overall ion exchange processes, it is very useful the determination of ion exchange isotherms at given temperature. Ion exchange selectivity can be characterized by plot of logarithm of corrected equilibrium constant (ln K_H^M) vs. equivalent fraction (X_M) of metalion in exchanger. It is pointed out that calculations of thermodynamic equilibrium constant and function are important for interpretation of ion exchange mechanism on particular exchanger.

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