There is a great deal of interest in the wide variety of mineral resources dissolved in seawater. Though the total amount of mineral resources dissolved in seawater is significantly larger than that on land, the elements are quite dilute, so it is extremely difficult to recover them effectively and economically.
We have developed various spinel types of manganese dioxide adsorbents (λ-MnO₂) with high lithium selectivity and effective granulation methods. We have also studied the practical recovery of lithium from seawater using granulated λ-MnO₂. In this paper, from the view point of lithium recovery, the present and prospective circumstances of lithium resources are initially outlined. The characteristics of a lithium recovery technology, such as the performance of lithium adsorbents, a recovery process using adsorption columns that we developed, are summarized, together with their application for practical lithium recovery from seawater using pilot plant.

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In order to put a fast breeder reactor (FBR) into practical use, it is necessary to resolve the problem of spent nuclear fuel and to establish an FBR fuel cycle. Since the minor actinoid (MA; Am, Cm etc.) mostly contained in the spent nuclear fuel is exothermic and a longer life radioactive nuclide, it complicates the final disposal issue. In recent years, as separation and recovery of MA from FBR spent fuel, the extraction chromatography process has attracted attention. However, we are concerned about the degradation of the separation ability with radioactive decomposition gas and sludge generation in the extraction chromatography system. In recent years, we have been investigating the development of fluid bed extraction chromatography techniques for spent nuclear fuel reprocessing. In this study, we tried to develop a mechanical fluid bed extraction chromatography system. We report that elution behaviors Bi(III) in nitric acid solution-contained gas and sludge with TOPO adsorbent was examined using the mechanical fluid bed extraction chromatography system. Furthermore, the separation behavior of Bi(III) from typical fission products (Sr(II)) in nitric acid solutions were investigated by using the mechanical fluid bed extraction chromatography system packed by a TOPO adsorbent.

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The metal corrosion products generated in the water systems of nuclear power plants (crud) should be efficiently removed from the water in order to maintain the safety and reliability of the plants' constituent materials and reduce radiation exposure to workers. Recently, we developed a new highly porous type of anion exchange resin product, “DIAION HPAN10”, which has high crud removal capability. The model crud removal capability of HPAN10 is ten times greater than that of conventional gel types. However, in general, highly porous resins, with highly-developed porous structures, have the low physical strength, and the level of turbid substances and eluate generated by the resin surface is very high. We improved and enhanced the physical strength of HPAN10 and as a result the level of turbid substances and eluate decreased to a practical level. In regards to the application of HPAN10 in nuclear power plants, we believe it is suitable for use with conventional gel type mixed bed resins which are used abundantly in primary water systems. For example, we recommend that HPAN10 is overlaid on the layer of mixed bed rein in a demineralizer, and, consequently, we think it shows high crud removal capability because of its synergetic effect.

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Adsorption of arsenic (As(III) and As(V)) has been investigated, employing magnetite (Fe₃O₄), titania (TiO₂), and alumina (Al₂O₃) as adsorbents. Three kinds of adsorbents possess high adsorption ability for both As(III) and As(V) in acidic and neutral pH region, which indicates the all adsorbents are applicable for the As removal from common geothermal waters. The maximum adsorption amounts determined by Langmuir isotherms are order of Al₂O₃≈TiO₂>Fe₃O₄ in the case of As(III), and Al₂O₃>TiO₂>Fe₃O₄ in the case of As(V), respectively. These adsorption abilities are affected by both of hydroxyl groups on the surface and specific surface area of the powdered adsorbents. Chromatographic removal of As(III) from aqueous solution was performed by using a laboratory-scale column packed with the granulated adsorbents of Fe₃O₄, TiO₂ and Al₂O₃. The effective removal of As(III) from aqueous solution could be effectively achieved using granulated TiO₂ adsorbent in the three kinds of adsorbents, due to its high adsorption kinetics.

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