When looking back my clay science researches, most of them are concerned with behavior of magnesium bearing clay minerals under hydrothermal conditions. In this short paper, my research history is briefly reviewed. My research begins with the study of the genesis and hydrothermal phase transformation of stevensite and sepiolite. And followed with the research of the effect of dry grinding of the hydrothermal reactivity on these clay minerals. At the present time, my interest is focused on the mineral chemistry of palygorskite, especially on dehydration and phase transformation on heating. In addition, some consideration on the feature of the Clay Science Society of Japan also presented.

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The Earth repeats selection in its 4.6 billion-year-history and produces a perfect circulation with least energy. We can learn two things from the circulation of nature. One is the perfect circulation systems of nature. Another one is that, although nature is selfish, it has created the perfect circulation. While human beings, because of their egoism, they are about to come to a head of destruction of civilization. It means that nature doesn't require any desire, where as a result, perfect circulation occurs. Comparing to that, human beings have consumed nature, origin of resources in order to satisfy their desire. In another words, we have satisfied our desire by treating nature as a tool like a slave. The mental desire of human beings is endless and such structure of desire is called "irreversible value of life". One can't abandon comfort and convenience once they experience them. It is therefore that, the new technology means to admit an expansion of desire, but it is not materialistic desire that modern philosophy brought. It is a conversion into the mental desire. It is not to treat nature as a slave but a value of the new creation of things where nature and human beings are equal. Nature technology is one of the solution and how it was born will be discussed.

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The adiabatic hydration calorimeter developed for measuring hydration enthalpies of zeolites is described with the possible improvement for more precise measurement, which may extend the application for quantitative measurement of heat of adsorption of water on clay minerals. As entropy value of H_2O derived from measured adsorption-heat specifies the energy state of the molecule as an independent component, this is useful for characterizing hydrophilic materials such as soil, wood, thermally insulating board and moisture-controlling board. Heat amount calculated of water-adsorption onto dust-particles in the dust and sand storm, for example, is so massive that it activates the low pressure to blow the dust far off.

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Carbon capture and storage (CCS) is important to control CO_2 emission into atmosphere. There are various CO_2 separation and capture methods: chemical absorption, membrane separation, hybrid methods of them and physical adsorption by pressure swing adsorption (PSA). In this study, the PSA method under high pressure condition was selected from the standpoint of energy efficiency. CO_2 adsorption/desorption on zeolite-13X and the HAS-Clay were conducted under high pressure up to 950kPa. In the range of 100-950kPa, the amounts of CO_2 adsorbed on HAS-Clay and zeolite-13X were 12.5wt.% and 5wt.%. The amount of CO_2 adsorbed on the HAS-Clay was 2.5 times greater than that of zeolite-13X with respect to atmospheric pressure.

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The weathering process has generally been considered from only a chemical/physical point of view, however recent observations of bacteria in weathered rocks have, led to questions about the importance of microbial activity. In order to examine this, an outdoor natural experiment has been performed in which an andesite rocky hill was immersed in running ground water at outside temperature for one year. The ground water is harvested from a depth of 150m for the establishment of the systems. The system was constructed in Kakuma Campus, Kanazawa University on April 2007, having the foot baths heated at 37℃ with disinfectant and the rocky hill with running natural ground water without any chemical and heating treatments. After 3 months of incubation in the footbath, biomineralization of carbonate minerals (calcite and aragonite) by Cyanobacteria was found. On the other hand, after one year, clay minerals (Smectite) and zeolite (Heulandite and Clinoptilolite) were found in only the rocky hill under natural conditions. Various kinds of microorganisms, such as Cyanobacteria, diatoms and bacteria accelerated weathering reactions of andesite (Tomuro-ishi) for building materials eroded on the surface, and to produce secondary minerals of bio-clays and zeolites. The microorganisms carry an important role to change water quality within such a short period. Large crystals of zeolite and fine thin films of smectite attached to the microorganisms with cohesion organics to form green microbial mats on the surface of the andesite rocky hill, showing accumulation of elements such as Al and Si which could have been derived by dissolution of the rocks associated with running water. These data collectively demonstrate the microbial formation of smectite and zeolite of bio-clays, where the reaction rates may be substantially enhanced by the presence of microorganisms. Bacteria and diatom activity may hence have a great influence on the clay mineral developments commonly observed in naturally weathered rocks. The mechanism of bio-clays formation has important implications for water-rock interactions both in natural environments and in polluted areas. The footbath facilities will be made available for use not only in research, but also for the advancement of education while contributing to the local community.

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Adsorption and post-adsorption characteristics of different oxyanions such as P, Cr, As and Se onto schwertmannite were investigated in order to understand the role of schwertmannite in acid mine drainage, and its performance and safety assessment in remediation system. Synthetic schwertmannite was used for the adsorption and post-adsorption experiments as a starting material. In the adsorption experiments, the starting material was reacted with various oxyanion solutions such as Na_2HPO_4, Na_2CrO_4・4H_2O, Na_2HAsO_4・7H_2O and Na_2SeO_4 with concentration up to 2.0mM at around pH 3.9. Dominant chemical species of the oxyanions in the experimental condition were thermodynamically calculated as H_2PO_4^-, HCrO_4^-, H_2AsO_4^- and SeO_4^<2-> by Geochemist's Workbench. The obtained adsorption isotherms showed that the schwertmannite has selectivity for oxyanions during adsorption with the affinity sequence being H_2AsO_4^->H_2PO_4^->HCrO_4^->SeO_4^<2->. This sequence corresponds to the sequence of decreasing ionic potential of the anions, which suggest that the observed selectivity of schwertmannite could not be attributed to the electrostatic interaction between the oxyanions and schwertmannite. It is known that oxyanions with low ionic potential have a tendency to form inner-sphere complexation with mineral surfaces. Therefore, the observed order of oxyanion retention may correspond to the sequence in affinity for the inner-sphere complexation on schwertmannite. This is also supported by the results of zeta potential measurement, which showed greater decrease of zeta potential after H_2AsO_4^- and H_2PO_4^- adsorption compared to other onyanions. In post-adsorption experiments (aging experiments), transformation to goethite was observed in X-ray diffraction patterns for the schwertmannite containing oxyanions with lower selectivity such as SeO-4^<2-> and SO_4^<2-> while there is no change in X-ray diffraction patterns of schwertmannite with H_2AsO_4^- and H_2PO_4^- even after 556 hours. Desorption of SeO_4^<2-> and SO_4^<2-> was observed prior to the transformation, although most of H_2AsO_4^- and H_2PO_4^- were retained onto schwertmannite. The desorption of oxyanions therefore resulted in the transformation of schwertmannite to goethite. Oxyanions with higher adsorption affinity, i.e., lower ionic potential, have a greater stabilizing effect on schwertmannite structure, although ordinary schwertmannite with SO_4^<2-> is metastable and easily transforms to goethite.

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