Copper (II) hexacyanoferrate (II) (CuFC) /Amberlite XAD-7 composite for cesium separation was prepared in the following manner. Trioctylmethylammonium chloride (TOMA) and trioctylpropylammonium chloride (TOPA) were used as a mediating agent to load CuFC in the pores of macroporous resin beads having no ionogenic groups. Amberlite XAD-7 was treated with TOMA or TOPA dissolved in acetone, and washed with a suitable solvent after evaporating acetone. The TOMA or TOPA loaded Amberlite XAD-7 was then treated with K₄Fe (CN) ₆ and CuCl₂ solution in this order to precipitate CuFC in the resin pores, and finally washed with acetone to extract the TOMA or TOPA. In this treatment, CuFC was found to be loaded on the resin without precipitating in the outer solution. CuFC content in the composite thus obtained was ca. 0.15 g (g resin) ^-1 at TOMA or TOPA loading of 0.9 g (g resin) ^-1. The sorption of cesium from 3 M NaNO₃ and the subsequent desorption with 5 M HNO₃ by use of the composites thus obtained were examined before and after the initial regeneration with hydrazine nitrate in 0.1 M HNO₃ solution. As a result, it was found that a repeated use of the composites was possible with a relatively high sorption of cesium and with a low release of copper ion when the composites were converted to a A₂Cu₃ [Fe (CN) ₆] ₂-rich form (A: univalent cation) under the same conditions as the those in the desorption and subsequent regeneration treatments prior to the initial sorption treatment.

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For planing of removal characteristics of phosphonate ion in electroless nickel plating solution, we have been studied about the adsorption characteristics in model solution by the use of granulated Yatsugatake volcanic ash soils (GY2) .
The results obtained are as follows;
(1) The rate-determining steps of adsorption for GY2 with mean diameter ≤1 mm were estimated to be a film diffusion controlled at the first stage, after that to be a particle diffusion controlled.
(2) In the case of GY2 with mean diameter ≥2 mm, the rate-determining steps of adsorption were estimated to be a particle diffusion controlled.
(3) The overall mass transfer volumetric coefficient (K_Fa_v) of GY2 with diameter 0.64-1.68 mm for phosphonate ion was 7.90×10^-3/s and this value is useful for planing of practical column treating equipment for plating solution with phosphonate ion.

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The composite membranes were prepared from cation exchange membranes and anion exchange membranes, and pyrrole by the chemical oxidation using ferric ions as an oxidizing agent, and electrodialytic transport properties of the membranes, relative transport number between two anions and other properties, were evaluated. According to the procedure to prepare the composite membranes, the membranes with different structure were obtained: polypyrrole existed homogeneously throughout the membrane or polypyrrole did only on the membrane surfaces as layers.
When a polypyrrole layer was formed on one side of the cation exchange membrane, the transport numbers of alkaline earth metal ions relative to sodium ions decreased remarkably. This is due to mainly sieving effect of cations by the highly tight polypyrrole layer and partially to the difference of electrostatic repulsion forces of weakly basic anion exchange groups of the polypyrrole to rations. On the other hand, the composite membranes composed of anion exchange membranes and polypyrrole showed the difficulty in permeating sulfate and bromide ions, and selective permeation of nitrate ions relative to chloride ions. The fact that selective permeation of nitrate ions, which are larger than chloride ions was observed in spite of the formation of the tight layer on the membrane surface means that the permeation of anions through the membranes was controlled by sieving anions with the layer and the affinity of the anions to the membranes depending on hydration degree of anions. The composite membranes from the anion exchange membranes also showed anti-organic fouling properties and high acidretention properties in electrodialytic concentration of hydrochloric acid solution.
Because the composite membranes have both electronic and ionic conductivity, other properties of the composite membranes, applications to lithium battery as the composite of anode active material and solid polyelectrolyte (composite membrane from anion exchange membrane), ferric and ferrous ion redox cell (composite membrane from cation exchange membrane) and a humidity sensors (composite membranes from anion exchange membrane), were also explained.

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Electrochemical host-guest reactions of manganese oxides were reviewed by illustrating an electroinsertion of Li⁺ into a Pt/λ-MnO₂ electrode and an electrointercalation of alkali-metal ions into a birnessite-type manganese oxide electrode in aqueous solutions.
A thin film electrode of spinel-type manganese oxide, Pt/λ-MnO₂, is prepared by the brush-ing-heating methods, followed by the electrochemical extraction of Li⁺ from the electrode. Equilibrium potential of the Pt/λ-MnO₂ electrode shows a near-Nernstian response to Li⁺ and not to other alkali metal or alkaline earth metal ions. The selectivity of the Pt/λ-MnO₂ electrode for Li⁺ is markedly high, even compared to that of organic ionophores for a lithium ionselective electrode. The equilibrium potential was stable and pH-independent over a wide pH range (pH 4 to 9.5) in a solution with the Li⁺ concentration above 5 mmol/dm₃. Cathodic and anodic potential sweeps cause an insertion and extraction of Li⁺ into/from the Pt/λ-MnO² electrode. The electrochemical insertion/extraction reaction originates from the redox reaction between trivalent and tetravalent manganese. The interfacial charge-transfer process is independent of the composition x in Li_xMn₂O₄, and the exchange current density is almost constant irrespective of x and relatively high (1.1×10^-3 A/cm²), indicating the fast ion transfer between the solid and liquid phases, whereas the chemical diffusion coefficient of lithium depends greatly on x because of the effect of the thermodynamic factor. The chemical diffusion coefficient of lithium is in the range of 10^-12 to 10^-10 cm²/s. The solid state diffusion of Li⁺ is a rate-deter-mining step in the electroinsertion.
A thin film electrode of birnessite-type manganese oxide is prepared with the chemical composition of K_xMnO_y, (x=0.33 and y-2) and an interlayer spacing c₀ of 0.697 nm. The anodic potential sweep in an aqueous solution causes the deintercalation of K⁺ with an increase in c₀ due to the intercalation of H₂O. The quasi-reversible intercalation of K⁺ occurs by the subsequent catholic potential sweep in a 0.2 mol/dm³ KCl solution. The electrochemical measure-ments show that K⁺ is not electrochemically active in the deintercalation/intercalation reaction but H⁺ is. The reaction proceeds based on the mechanism consisting of an electrochemical reaction (the redox reaction between Mn³⁺ and Mn⁴⁺) and an ion-exchange reaction between K⁺ and H⁺. The intercalation experiments in various alkali-metal chloride solutions show the intercalation capacity in order of Na-K>Li>Rb>Cs.

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The authors' works on adsorption behavior for metal ions of oxine type of chemically modified chitosan which was crosslinked after complexation with gallium or ferric ion as a template ion are reviewed. Adsorption of rare metals such as gallium, indium, molybdenum (VI), and vanadium (IV) as well as common metals such as zinc, aluminum, and iron (II) from sulfuric acid solution on gallium-templated oxine type of chitosan was examined and these rare metals were found to be selectively separated from the common metals. That of rhodium (III) from hydrochloric acid solution containing tin (II) on iron (III) -templated oxine type of chitosan was also examined and it was found to be selectively and effectively separated from platinum (IV) and copper (II) .

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