In order to study the redox reactions of metal complexes in the ion exchanger, the reductiveelution behavior of Fe (III) chloro-complexes adsorbed in an anion-exchanger from hydrochloric acid solution to non-adsorptive Fe (II) was examined by using several reductants. The chloro-complexes formation behavior and anion exchange characteristics of the metal ions in hydrochloric acid solution were investigated. The current-potential curves of Fe (III) /Fe (II) in hydrochloric acid solution of concentrations from 0.1 to 9.0 mol⋅dm^-3 were measured by the cyclic voltammetry and the effects of chloro-complexes formation on the redox potential were examined. The reductive-elution experiments of Fe (III) chloro-complexes were carried out by column method using V (III), Ti (III) and Sn (II) as a reluctant respectively, and the elution behavior were discussed.
The redox potential of Fe (III) /Fe (II) decreased with increasing hydrochloric acid concentration, revealing that the reduction of Fe (III) to Fe (II) becomes difficult due to the formation of chloro-complexes.The reductive-elution rate of Fe (III) chloro-complexes from the ion-exchanger was found in the order of Ti (III) >Sn (II) >> (III), and the redox potential of the reductants was considered to be a predominant factor effecting the elution rate. On the other hand, the adsorptive reluctant Sn (II) was separated from the Fe (II) eluate, while the non-adsorptive reductants Ti (III) and V (III) mixed in the Fe (II) eluate.

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In a boundary layer formed on the desalting surface of an ion exchange membrane, natural or forced convection is produced. The ionic transport in the boundary layer is, accordingly, reasonable to be expressed by the extended Nernst-Planck equation taking account of the convection term. Limiting current density is not only the phenomenon of a membrane but also that of an apparatus. The limiting current density of the membrane is measured using the apparatus in which the flow pass length in a desalting cell is small or the distance between the membranes is large. Limiting current density of an electrodialyzer is obtained under the assumption that the distribution of solution velocities in each desalting cells are expressed by the normal distribution, and that the limiting current density condition is realized on a cation exchange membrane at the outlet of a desalting cell in which the solution velocity is the least.
Water dissociation arise in a water dissociation layer formed at the interface between a membrane and a boundary layer at above the limiting current density. The water dissociation arisen in the water dissociation layer is extremely accelerated comparing the phenomenon in a solution. The water dissociation arisen on an anion exchange membrane is generally more accelerated than that on a cation exchange membrane. This is because the second Wien effect of quaternary ammonium groups in the anion exchange membrane is larger than that of sulfonic acid groups in the cation exchange membrane. On a cation exchange membrane placed in a magnesium chloride solution, however, violent water dissociation occur. This is brought about by catalytic chemical reaction of OH groups in magnesium hydroxides precipitated on the desalting surface of the cation exchange membrane.

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Clay- and zirconium phosphate-supported metal complexes were prepared by various methods such as cation exchange, chemical anchored ligand, and interlayer polymerized ligand methods. Multiple modification of smectites with metal complexes and various organic guests (tuning guests) can be applied to the preparation of catalysts for the molecular recognition reactions such as shape selective, chemoselective, regioselective, and asymmetric hydrogenations. Especially, chiral phosphine-Rh complexes intercalated in hectorite exhibited both of size and asymmetrical recognition simultaneously in the hydrogenation of itaconates.

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As a result of reserch and development works carried out in the past nearly half century, the elelctrodialysis technology has been commercialized in wide industrial fields, and is still utilized for seawater concentration in salt manufacturing, desalination of brackish water, recovery and reuse of wastewater, and demineralization of nonelectrolyte and so on. Further, paticular membrane of special property is applied for the separation of strong acid or alkali in diffusion dialysis process.
For the realization of above mentioned application of the ion-exchange membrane, not only innovation of membrane itself but also improvement of electrodialysis equipment and development of design technology of the process played major roles.
This paper introduces briefly some results of development works in the fields of application technique, mainly carried out by the R & D group, the author was responsible for the works.

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About fifteen years ago, Nitivy Company had produced Strong Cation powder type (IEF-SC-3050) ion exchange fiber on a commercial basis.
Continuously we have developed filament type ion exchange fibers (Strong Cation, Strong Anion, Weak Cation, Weak Anion type), which are able to modify and have now established the technology of mass production of such fibers.
Their ion exchange fibers made from Polyvinyl alchole polymer and water soluble polymers of which introduced various functional groups.
They are different from the conventional ion exchange resins in the method of manufacturing.
Therefore, they have the following features compared with the conventional ion exchange resins.
(1) They have a large surface area and are fast in rate of reaction.
(2) Filter paper form, non woven form, woven and kitted fabric form, etc. can easily be made of its.
From the above-mentioned features, we are confident that “Nitivy Ion Exchange Fiber” is usefull to you in many fields.

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