Low-silica zeolite samples and smectite were hydrothermally synthesized from Si-Al hydrous oxides. The synthesized zeolite phases changed to structures having lower Si/Al ratio with increases in the amount of NaOH in the slurry, and time of hydrothermal treatment. When tetraethyl ammonium hydroxide (TEAOH) was added instead of NaOH, ammonium smectite was produced without zeolite. SEM and TEM images suggested that crystallization occurred at the solid-liquid interface. Upon addition of NaOH (Na/Si<0.2) to the smectite, zeolite nucleation was observed on the surface of the clay film. The zeolite phase changes depended on the dissolution of the solid phase and the resultant change in composition of the liquid phase. The observed phase relationships agreed with the calculated formation free energies and solubilities. Thus, low-silica zeolite formation under hydrothermal conditions was strongly affected by the composition and concentration of the solution. The phase relationships based on solubility curves, can be used to control the synthesis of metastable aluminous silicates and can be applied to the design of some industrial materials such as zeolite membranes and molecular sieves using hydrophilic low-silica zeolites and smectites.

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High-grade lead-zinc-silver are occurs in the Toyoha vein-type deposit, which is located 40 km southwest of Sapporo, Hokkaido, Japan. Several K-Ar ages from 3 Ma to 0.5 Ma were reported for the mineralization. It was originally regarded as one of typical epithermal are veins, but can now be considered a polymetallic vein-type deposit, because of the discovery of tin, indium, tungsten and molybdenum minerals from the veins. Main gangue minerals are quartz, calcite, rhodochrosite, chlorite, sericite and kaolin mineral. Illite occurs at the upper levels, and gives place to chlorite at the lower. As a whole, the boundary seems to be a shallower than-150 meter level in the northwestern veins of the mining area, and declines to about-400 meter level in the southeastern veins. Chlorite is one of the abundant hydrothermal minerals throughout the alteration zones of Toyoha deposit. Iron content in the chlorite tends to increase generally toward the ore veins and the chlorite in gangue mineral is almost pure iron-chlorite. Iron-rich chlorite can be formed by an are solution which is in equilibrium with rocks at high temperature and reaches to an ore deposition site.

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Clay mineral assemblages have been widely used in multidisciplinary stratigraphical studies. This paper presents the results obtained in the study of a Lower Cretaceous depositional sequence from the Lusitanian Basin (Portugal). The Upper Hauterivian to Lower Barremian section at Guincho Fort (30km West of Lisbon) has been studied in a detailed bed-by-bed sampling corresponding to a total of 85 samples. The mineralogical composition of bulk sample and clay fractions (<2μm) has been determined on non-orientated and orientated specimens by X-ray diffraction. Multivariate statistical methods were used to establish the relationships existing within a large set of variables, which included results obtained from other traditional methods of stratigraphical analysis (paleontology, sedimentology, facies analysis, geochemistry). Clay mineral assemblages have contributed to the paleoenvironmental and paleogeographical reconstruction of the studied interval and have improved the sequence stratigraphic interpretation and positioning of sequence boundaries and other sequential surfaces (transgressive and flooding surfaces). Finally, it has been possible to establish relations of the overall results to the sedimentary record of orbital pattern variations.

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Chemical bulk analyses of intermediate alunite-natroalunite minerals indicate anomalous high contents of REE, Sr, Ba, Ca and P. Alunite occurs as veinlets or nodules cross-cutting hydrothermal clay deposits, containing pyrophyllite, kaolinite and sericite in the west Barker area (Dristas & Frisicale 1983 ⁽⁵⁾ , 1992 ⁽⁶⁾ ). Petrographic studies reveal a pseudocubic habit for the alunite. No significant zoning has been detected in this mineral by EPMA backscattered images. Additionally, EPMA and EDX studies indicate that the tabular-like inclusions in cores of alunite contain significant amounts of P, Ba, Sr, REE, Ca and Fe. Alunite shows epitaxial growth on the inclusion mineral. These tabular-like inclusions correspond to APS (aluminium phosphate sulphate) minerals, such as florencite, formed at early stages before alunite crystallization from a solution with a high phosphorous/sulphur ratio. The crystal structure of APS minerals are suitable for REE, Sr and Ba substitution since metal cations are situated in large cavities formed by 6-membered rings of M (O, OH) ₆ octahedra. A later increase of solution sulfurization would favor the formation of alunite that constrained the REE, P, Sr, Fe, Ca and Ba fixation.

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Ag⁺-imidazole chelate supported montmorillonite has been synthesized by a conventional cation exchange reaction in an aqueous medium at ambient temperature. The results of X-ray diffraction and elemental analysis indicated that the most part of the interlayer exchangeable cations were replaced by the silver chelates. The resulting material was subjected to an antimicrobial activity examination, and its interlayer structure was determined. Minimum inhibitory concentration tests using the microbes indicated that the synthesized agent had significant antibacterial and antifungal characteristics against two kinds of bacteria and six kinds of fungi. The imidazole ligands in the montmorillonite interlayers were decomposed and became carbon by heating temperature of around 300°C in an air atmosphere. The structure of the intercalated specimen was estimated by the (00l) relative intensities which were observed by X-ray diffraction. Based on the change in the basal spacing after the reaction, and the structural model calculation of the composite, it was concluded that the planar silver chelates were monolayer with flat orientation in the silicate layers.

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Ludox-AS40, Colloidal silica, Ludox HS-40 and Fumed silica were used as silica sources, in order to prepare well crystalline Na-magadiite and Na-kenyaite layered silicates. The influence of reaction times, NaOH concentration and water contents in the mixture gel were investigated. Pure Na-magadiite phase was obtained after a hydrothermal treatment of Na₂O/5SiO₂/122H₂O gel, at temperatures below 150°C for a period of 2 days reaction, independently of the silica source. However, better crystallinity was achieved using Ludox AS-40. Pure Na-kenyaite was formed only from Fumed silica at 170°C and after 2 days of reaction. The water content affected the type of layered silicates when fumed silica was used. Indeed, pure Na-kenyaite was obtained at 150°C and after 2 days of reaction using a gel of Na₂O/5SiO₂/24H₂O. Meanwhile, Na-magadiite was formed for a content of water above 70. A minimum content of NaOH (0.25Na₂O) was required to obtain Na-magadiite from Fumed silica and colloidal silica. The control of the transformation rate of Na-magadiite to Na-kenyaite or vice versa can be achieved by increasing the synthesis temperatures, or the gel compositions. We were able to block the transformation of Na-magadiite to Na-kenyaite by adding an organic solvent dioxane, and pure RUB-18 phase was obtained at temperatures above 130°C after 1 day of reaction.

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SEM observation of the aqueous suspension of kaolinite from Birdwood (South Australia) and Georgia (USA) show noticeable differences in microstructure. Birdwood kaolinite dispersion gels at very low solid loadings in comparison with Georgia KGa-1 kaolinite dispersion which remains fluid at higher solids loading. To explain this behaviour, particle interactions in the colloidal size fraction of Birdwood kaolinite have been proposed. These interactions may be brought about by the presence of nano-bubbles on clay crystal edges and may force clay particles to aggregate by bubble coalescence. This may explain the predominance of edge-edge (EE) contacts in suspension of Birdwood kaolinite. Such mostly EE linked particles build long strings that form a spacious cell structure. Hydrocarbon contamination of colloidal kaolinite particles and poor crystallisation are discussed as possible explanation of the unusual behaviour of Birdwood kaolinite. In Georgia KGa-1 kaolinite dispersions instead of EE contact between platelets displayed in Birdwood kaolinite, most particles have edge to face (EF) contacts building cardhouse structure. Such an arrangement is much less voluminous in comparison with the Birdwood kaolinite cellular honeycomb structure observed before in smectite aqueous suspensions. Such structural characteristics of KGa-1 kaolinite particles enables higher solid volume fractions pulps to form before significantly networked gel consistency is attained.

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The ion-exchange reactions of Na-magadiite with metal cations such as H⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cu²⁺ and Zn²⁺ were studied in an aqueous medium. The H+ ion and all divalent metal ions except Mg²⁺ exchanged with Na⁺ in an aqueous solution with a stoichiometric amount of the metal ion. K⁺ and Mg²⁺ showed poor reactivity with the Na-magadiite. Na⁺ was not fully replaced even with a K⁺ or Mg²⁺ concentration that was 100 times the Na⁺ concentration. The pH dependence of Cu²⁺ for the ion-exchange reaction was different from that of other metal ions. XRD analysis revealed that the structure of the Na-magadiite differed from the Cu-or H-magadiite. These differences arose from structural changes in the silicate sheet due to the H⁺ or Cu²⁺ adopting a different geometry in interaction with the oxygen atoms in the silicate sheet. Ethylene diamine (en) and pentaethylene hexamine (pentaen) react with Cu²⁺ to form stable cationic complexes: Cu (en) ₂, which has a planar structure, and Cu (pentaen), which has an octahedral structure. The XRD patterns all revealed a difference between the basal spacings of the metal-magadiite and the sum of the crystalline ionic diameter of the metal and basal spacing of the H-magadiite. Na⁺ remained in the interlayer of the magadiite in the presence of excess complexes. The degree of dehydration of the metal cation depends on the ion-exchange reactivity of the magadiite.

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A simple means for fabricating a clay/cationic organic molecule hybrid monolayer is proposed. A chloroform solution of a hemicyanine derivative was spread onto a suspension of sodium montmorillonite. Then the hybrid film formed was deposited onto a substrate without any compression process onto a substrate. The obtained films were characterized by using atomic force microscopy and UV-vis spectroscopy. As a result, it was found that a hybrid film similar to a clay-organic hybrid Langmuir-Blodgett (LB) film was formed even when this means was applied. The optical second harmonic generation measurement revealed that the hemicyanine derivative molecules in the film were highly oriented. It is known that the fabrication of a hemicyanine dye LB film with a highly oriented hemicyanine dye array requires a long time. By utilizing this means, we have demonstrated that a film with a highly oriented molecular array can be fabricated in a considerably shorter time than employing conventional LB technique.

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Nanocomposite gels were prepared by mixing clays with gelatin. The clay was either of plate-like (montmorillonite, laponite) or fibrous morphology (sepiolite). The dispersion of the clay was monitored by X-ray diffraction and the gel structure was scrutinized by low temperature scanning electron microscopy. The mechanical properties of the gels were investigated by conventional dynamic mode rheological measurements in stress-imposed mode. The results show that plate-like particles (montmorillonite, laponite) are extremely effective for increasing the gel formation temperature, whereas fibrous particles are not. A correlation was found between the gel formation temperature and the cell size of the gel, as observed by cryo-SEM. Surprisingly, in spite of the strong smectite-induced shift of the gelation temperature, the mechanical properties of the gel were unaffected, in the investigated concentration range. Thin (a few tens of micrometers) self-standing and well transparent films are easily obtained by drying. These organic-inorganic hybrid gels and films are attractive materials for several applications, including biomedical treatments and conservation of antique wall paintings.

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The purpose of this work is to study the particular physical properties of interlayer water in clay-water systems. Five smectites are studied at different hydric potentials in a range of relative humidity between 5 and 97%. Regardless of these RH conditions, the interaggregates space is never saturated with water. The d001 basal spacing of the clay sheets changes according to the evolution of water content. These facts lead us to conclude that the interlayer space is the main location where the hydration occurs, i.e., where we expect the physical properties such as the water density to be different from bulk water.
The density of the interlayer water and the solid density are simultaneously measured by means of a helium pycnometer. When measuring the total volume of a powder with this method, a correction is needed to take into account the volume occupied by water. Corrections using a density of the water equal to that of pure water did not give satisfactory results. To obtain an agreement with the experimental results, we had to recalculate the density of the interlayer water. These values are found to lie between 1.14 and 1.18g/cm3 for the studied clays. Water can be considered as free water in swelling clay only for RH domains close to saturation, more than 97% RH. Under this level of saturation, water is considered as a smectite component just as the silicate skeleton or cations. The whole components constitute a lamellar structure with a hydrous and electrical continuum and define a smectic phase.

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The dissolution behavior of smectite under alkaline conditions at 25° to 50°Cwas investigated using in-situ Contact mode atomic force microscopy (CMAFM) and Tapping mode AFM (TMAFM). Smectite particles dissolved via the retreat of the edge surfaces without the affect of the AFM tip, except in some series of the dissolution experiment in CMAFM. No etch pits were observed forming on the basal surface within the experimental durations. The edge surface area (ESA)-normalized dissolution rates of smectite at a certain pH and temperature condition, therefore, have a constant value independent of the particle size, indicating the essential dissolution rate. In contrast, the dissolution rates normalized to the total surface area (TSA) of smectite varied with the particle size. The activation energy of smectite dissolution under alkaline conditions appears to be dependent on pH, like as kaolinite. A model dissolution rate equation which includes simultaneously the effect of pH and temperature was deduced from the effect of the activation energy on pH, the rate equation of smectite dissolution at 25°C, and the Arrhenius equation. The rates estimated using the model are in good agreement with experimental dissolution rates between 20°and 60°C.

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Complex impedances are measured on cation exchanged layered silicates, H-, Na-and K-kenyaites (M₂Si₂₂O₄₅·xH₂O, M=cation) to investigate proton conduction in these materials. The impedances in every compound showed strong dependence on relative humidity. Proton conductivities were estimated to 8.2×10^-7, 7.2×10^-5 and 1.1×10^-3S cm^-1 for H-, Na-and K-kenyaites, respectively, at 95% relative humidity.

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We study the diffusion of water in weakly-hydrated samples of the smectite clay Na-fluorohectorite. The quasi one-dimensional samples are dry compounds of nano-layered particles consisting of-80 silicate platelets. Water diffuses into a sample through the mesoporosity in between the particles, and can subsequently intercalate into the adjacent particles. The samples are placed under controlled temperature. They are initially under low humidity conditions, with all particles in a 1WL intercalation state. We then impose a high humidity at one sample end, triggering water penetration along the sample length. We monitor the progression of the humidity front by monitoring the intercalation state of the particles in space and time. This is done by determining the characteristic spacing of the nano-layered particles in situ, from synchrotron wide-angle X-ray scattering measurements. The spatial width of the intercalation front is observed to be smaller than 2mm, while its velocity decreases with time, as expected from a diffusion process.

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We studied the intercalation of (3-aminopropyl) triethoxysilane (APTEOS) and (3-aminopropyl) diethoxymethylsilane (APDEOS) into Na-montmorillonite interlayers by using XRD, NMR, and FT-IR. It was suggested that APTEOS is not intercalated in the interlayers of montmorillonite as “random” polymerized structures, but as “cage” structures of “Siloxane Cubic Octamer”(SCO). To clarify the structures of organosilicate materials in the interlayers, we compared the intercalated compounds derived from APTEOS with those from pre-synthesized SCO. ²⁹Si NMR spectra of both intercalation compounds were very similar and mainly showed the peak at-68 ppm of the Si Q³ structure due to the SCO. The basal spacing of both intercalated compounds had similar values and changed with the amount of APTEOS. The changed basal spacing was explained by the direction of aminopropyl chains in the interlayers. These results supported the SCO structure model in the interlayers. We also investigated Brunauer-Emmet-Teller (BET) adsorption properties of intercalated compounds. Changes of pore radius and surface area were well explained by the SCO model. In the case of APDEOS intercalation, polymer structures of poly (dimethylsiloxane) were intercalated as indicated by the peak at-22 ppm of ²⁹Si NMR. The intercalation behavior of APDEOS was different from that of APTEOS.

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The EXAFS samples were Kunipia F-type smectite exchanged with Cs at a concentration of 2 mol/kgclay at pH 3.9 and 9.8. The K-edge absorption spectra were collected in the transmission mode at the SPring-8 (8.0 GeV), Japan. The molecular dynamics (MD) simulations were performed on beidellite. The system consisted of two 2: 1 sheets and two inter-layer spaces including water molecules. The total number of atoms in the system was 2, 672 and 4, 112 at hydration 2.5 and 7.5 H₂O, respectively. The force field consisted of four types of potential: Coulomb, van der Waals, Short-range repulsion, and covalent. The Cs-O distances in wet-paste samples were 3.12-3.19 and 3.60-3.74 Å for the first and second shells, respectively. The coordination numbers were 60 and 3-40 atoms. In air-dried samples, the Cs-O distances were 3.08-3.18 and 3.55-3.73Å. The coordination numbers were 50 and 5-60 atoms. The adsorption sites were identified as three types of stagnation points of the moving Cs atoms in inter-layer water. In air-dried samples, Cs atoms were predicted to be located over a hexagonal cavity of 2: 1 sheets or over a corner oxygen atom of a tetrahedron. In contrast, in wet-paste samples, Cs atoms hovered over a side of the tetrahedron as well as a hexagonal cavity.

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Photochemical electron transfer reactions of cationic porphyrins on an anionic-type clay (Smecton SA) surface were investigated. Two types of complexes were formed between the cationic porphyrin and the anionic-type clay depending on the conditions. In the first type, the porphyrin molecules are adsorbed on surfaces of the individual dispersed clay sheets or layers (exfoliated complex). In the second type, the porphyrin molecules are intercalated between the stacked clay sheets (intercalated complex). For the exfoliated complex, we have found recently that the porphyrin molecules adsorb in a flat orientation on the clay sheets as monolayers, without discernible aggregation. The high packing density is determined by the fact that the positive charges on the porphyrin precisely neutralize the negative charges on the clay surface. Fluorescence quenching experiments of porphyrins in exfoliated and intercalated complexes by hydroquinone and ascorbate as electron donors were carried out. The quenching rate constant was affected by the charges of the electron donor in solution. When hydroquinone was used as a neutral electron donor, an efficient electron transfer was observed both in exfoliated and intercalated complexes. The fluorescence quenching experiment for the intercalated complex indicated that the diffusion of hydroquinone is restricted in the interlayer space.

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Conventional laboratory x-ray diffraction techniques are generally used to characterize minerals in oil sand ores and other extraction process streams and can usually provide mineralogical insight into reasons for poor processability. Often, however, a greater level of detail is required to quantify low levels of mixed layering in clay minerals and the multitude of non-clay minerals in the ores. The more intense x-ray sources available at synchrotrons with their inherent high resolution and tunable wavelength can often help in providing this level of detail. In addition, x-ray microscopy can help to characterize the organic contaminants that commonly affect clay behaviour in industrial processes. In this study, low levels of mixed layering of smectite were observed in the kaolinite and illite phases using synchrotron x-ray diffraction, in addition to heavy minerals undetectable using a laboratory rotating anode x-ray source. Using scanning transmission x-ray microscopy, the speciation of carbon components adsorbed on clay minerals after bitumen extraction suggests a preferential affinity of the clay minerals for high-molecular-weight aromatics in bitumen.

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Illite as a mineral of the mica group was investigated to obtain information concerning its cathodoluminescence and infrared absorption. The study included analyses by scanning electron microscope (SEM), cathodoluminescence (CL) spectroscopy and microscopy as well as infrared (IR) spectroscopy on muscovite as a reference mineral and illite from Füzérradvány, NE Hungary. CL image of illite shows relatively bright, crystallographically controlled bands and zones in the otherwise CL-dark background. Cathodoluminescence spectrum of illite from Füzérradvány shows a broad band centered at 589 nm. Illite shows eleven FIR peaks at 94, 118, 193, 260, 334, 384, 419, 473, 505, 528, and 544 cm^-1, and exhibits MIR spectral features at 538 (bending vibration of SiO₄^4-), 1038 (stretching vibrations of SiO₄^4-), 1664 (bending vibrations of H₂O), 3481 and 3641 cm^-1 (stretching vibrations of OH group). In general, illite shows low intensity in the CL image and spectrum, indicating that this mineral lacks recombination centers or electron traps for the cathodoluminescence emission. It indicates that illite was formed at high temperature. CL and IR properties of illite provide useful information on its origin and microdeformations.

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For the purpose of screening of zeolite membranes, which are highly resistant to acid, merlinoite (MER) and phillipsite (PHI) membranes were synthesized for the first time, and pervaporation (PV) performance of those membranes were evaluated using 5-95wt% ethanol solution. Each zeolitemembrane was synthesized on a mullite tube by secondary growth of seed crystals, which were rubbedon the outer surface of the tube. The permeance of pure N₂ through those membranes was below1.4×10^-9mol/m²/Pa/s at 50°C. By SEM observation, the thickness of the membrane was 10-50μm. InPV performance, each membrane showed hydrophilic behavior. When ethanol concentration was 90wt% in the feed solution, the permeation fluxes (Q) of the MER and PHI membranes were 0.8-1.1kg/m²/h at 75°C. The water/ethanol separation factor (°) was over 10, 000 for MER membrane. In the evaluation of stabilities of the zeolite against acid, the changes in the XRD pattern and the compositionof MER and PHI were much smaller in comparison with the case of FAU and CHA. Thus, it can beexpected to use MER and PHI membranes for dehydration directly from the acid solutions likebiomass.

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In the last decade, many new industrial applications of clays have been developed. The main reasonsfor these new and modified applications are because clay suppliers have a better understanding of thephysical and chemical properties of the clay minerals. The clay industries have instituted better mining practices and improved processing. The clay deposits and products covered in this paper are commonclays that consist of shales, underclays, glacial lacustrine clays and clay rich soils; bentonites, kaolinsincluding ball clays, and palygorskites-sepiolites.
The applications of these clays are largely dependent on their structure, physical and chemical properties, including color and brightness, particle shape, size, and distribution, surface charge and area, viscosity, and other properties that are specific for certain applications. The differences in the clayminerals are discussed which demonstrates why kaolins are a good paper coating mineral, ball claysare excellent ceramic raw materials, sodium bentonites are superior drilling muds, calcium bentonitesare good absorbents and bleaching earths, and palygorskite and sepiolite are very useful as suspending agents in certain liquids with a high salt content.

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Tunisian and Portuguese smectitic clays are under study to assess their potentialities to be used as naturalraw materials for the production of Light Weight Aggregates which have an important function in civilconstruction work. Several smectitic clay deposits from the meridional Atlas domain (Tunisia) and fromthe Meso-Cenozoic Lusitanian Basin (Portugal) were studied for this purpose. Characterization of theseclays includes mineralogical and chemical analysis, dosage of total organic carbon, grain size analysis andthermal analysis. Small balls (1 to 1.5cm in diameter) were prepared with these clays in the plastic stateand were submitted to the firing temperatures ranging from 1050up to 1180°C, during time intervalsranging from 5 to 15min. Special additives like motor oil, phosphate residues and sand, in differentproportions, were mixed with the smectitic clays in order to obtain better expansion. The followingproperties were determined on the bloated balls: apparent density, mechanical resistance corresponding tothe rupture under compression point and water absorption. The bloated balls showed appreciableproperties. Each additive has positive effects but in dependent on the original clay material. The resultswere comparatively appraised not only between Tunisian and Portuguese clays but also with commercialproducts.

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The synthetic methods of mica corresponding to natural production situations are developed. The crystalsof synthetic mica produced by the melting method become large. Some types of synthetic mica (fluoro-phlogopite, Na tetrasilisic mica, etc) can be produced by the melting method. The greatest use of synthetic mica is cosmetics, especially make-up cosmetics. The high aspect ratio particle with transparent luster is obtained only from fluoro-phlogopite (KMg₃AlSi₃O₁₀F₂). Transparent luster hides a blotch or wrinkles, and it is shown like a bright natural skin.
In melting method, Na tetrasilisic mica (NaMg_2.5Si₄O₁₀F₂) that is swelling mica can be synthesized. Thecrystal of Na tetrasilisic mica is larger than that of natural clay. The gas barrier film that was coated with Na tetrasilisic mica and poly vinyl alcohol was devised for food packing. Na tetrasilisic mica synthesized by melting method has high aspect ratios. The film coated with Na tetrasilisic mica demonstrates a highbarrier nature.
Synthetic mica is used for various applications like pearl mica pigments, filler, paint, and nanocompositematerial besides this.

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he clay particle morphologies in dilute aqueous suspensions of swelling clay minerals such as smectitesusing rheological techniques have previously been evaluated by applying Einstein's or Robinson's Newtonian equation, because there is little or no interaction between the particles in the system. However fortypical industrial aqueous suspensions of bentonite these equations are not applicable, because thesuspensions are non-Newtonian, i.e., plastic, in flow behavior and have an additional shear stress due to theparticle interaction. The relation between the shear stress, τ, and shear rate, σ, is described by the equationτ=η2σ+ αInσ+b. In this equation, the first term, i.e., the Newtonian term, is ascribable to hydrodynamic effects. The second and third terms are shear stress due to exclusively breaking and reformingthe particle interactions. Thus Robinson's equation was applied to the plastic viscosity or the Cassonviscosity of industrial bentonite suspension at high concentrations, and the effective volume of the particleswas presented. Then the effective volume was compared with each specific volume at the liquid limit and theswelling power.

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My work on ceramic technologies was started with clays as raw materials. Gradually, it has not only spread in the ceramic technologies but also focused on the kaolinitic clay science. My stand point is to understand the ceramic technologies from the clay science such as the deposition mechanism of kaolinitic sediment, effects of humus matters, exchangeable cations, the variety of crystallinity of kaolinites and so on. Moreover, water plays an important role in the fine particles (such as clay particles)-water system. My colleagues and I found that unfrozen water can coexist with frozen water even at liquid nitrogen temperature in the fine particle-water system, and succeeded to evaluate the unfrozen water quantitatively with DSC-measurement. We also succeeded to synthesize artificially platy kaolinite and α-Al₂O₃ powders with controlled atomic arrangement, crystallinity, aspect ratio and so on under hydrothermal conditions. In this paper, I will introduce four major results of our studies: 1) evaluation technologies of properties for clay and plastic materials, 2) synthesis technologies of both spherical and disordered kaolinites and platy α-Al₂O₃ powders, 3) proposition to the ceramic forming technology from the results obtained from studies on fine particle-water systems and 4) development of humidity controlled materials with controlling nano pore size and hardening by heating from natural resources such as kaolinite, allophane, imogolite, diatomaceous shale, gibbsite and other compounds.

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Cementitious materials and bentonite are planned to be used as engineered barriers for disposal of radioactive wastes from nuclear fuel reprocessing. After a repository has been closed, groundwater may permeate cementitious barriers, and hyperalkaline water containing Na, K and Ca ions may leach out. When the water comes into contact with bentonite, physicochemical changes resulting in degradation of barrier performance might occur. Furthermore, ion concentration of cement leachate may increase due to dissolution of nitrate in the waste. To investigate the hydraulic characteristics of bentonite under a disposal environment, hydraulic conductivity tests were performed using simulated cement leachate. It was shown that interlayer cations were exchanged with cations in the permeant solutions and the hydraulic conductivity of bentonite increased as the solution's cation concentration increased, and the hydraulic conductivity of the soak-treated bentonite increased as free swell decreased. This study demonstrated that bentonite changed physicochemically by penetrating the simulated cement leachate, and both cation concentration of permeant solution and the dominant interlayer cation of smectite had a great impact on the hydraulic characteristics of bentonite.

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Pyrite-bearing rock is readily oxidized when exposed to the atmosphere. Effluent from the impoundment of the rock commonly becomes acidic and enhances the mobility of heavy metals that are fixed or adsorbed on solid phases. Clay-rich covering soil is expected to be effective in reducing the oxidation rate of pyrite in the crushed rock, since the soil restricts the supply of gaseous oxygen to the rock. In this study, we constructed a miniature impoundment of truncated-pyramid shape, consisting of crushed igneous rock covered with a 1.7 m thick layer of silty soil, in order to observe gaseous oxygen concentration profiles. The soil used has a hydraulic conductivity of 3×10^-8 m/s and a porosity of 0.53. Interstitial gaseous oxygen within the crushed rock decreased with time to-1.5% due to oxidation of pyrite within the rock. The silty soil interrupted oxygen transport to the extent that the oxidation rate of the crushed rock was reduced by 93% compared with equivalent rock without a soil cover.

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The reduction of structural iron inside the TOT layer of a smectite has been performed for a long time through a complex mechanism. So far one chemical method shows some efficiency: reduction with dithionite in a citrate bicarbonate buffer. An alternative reducing agent, the metallic iron, through its corrosion process, was also studied here. The introduction of a small amount of Fe (0) has a significant impact on the smectite stability. Most of the reduction is done once the metal is consumed while a 7Å phase is formed. Another anomalous redox behavior appears during the oxidation of a Fe (II) exchanged smectite. After two months in an aerated environment, the Fe (II) inside the interlayer space is only partially oxidized and its Mossbauer quadrupolar splitting is very unconventional. Both experiments show that redox in smectite cannot be determined by the chemistry of the bulk solution. Globally these experiments raise major question about i) the water states in the interlayer and ii) the pH and Eh measurements within the smectite phase. These data are important in order to perform robust modeling of swelling clay reactivity.

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The transformations induced on argillaceous materials under thermal stress and the impact on their confining properties is a critical parameter, for example, in the nuclear waste storage. The samples were collected close to a basaltic intrusion in an argillaceous formation (argillites of Laumiere, Aveyron, France), which represents a natural analogue of thermal stress. The clay minerals characterization was conducted by the association of X ray diffractometry (XRD) and far infrared spectrometry (FIR) that allow to show an illitization of the highly illitic I-S minerals at basalt contact. The illitization is a phenomenon primarily dominated by the thermal influence. The weak and nonmonotonous variation of I-S crystallinity indexes corresponds to the influence of the geological context. The illitization is not monotonous because of superimposed processes. Those phenomena that had disturbed the heat transfer and the illitization are related to the geological context. Firstly, hydrothermalism was developing through the network of cracks. The high water/rock ratio had induced the basaltic chemical species transfers. Secondly, the presence of sedimentary heterogeneities as a limestone deposit had constraining the uniform dissipation of the heat. Laumiere study highlighted critical parameters that have influenced the evolution of argillaceous materials in thermal context.

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In-diffusion experiments for Cs⁺ ions in compacted Na-smectite were performed in the directions parallel and perpendicular to the orientation of the smectite particles as a function of smectite dry density (between 0.9 and 1.4Mg/m³), salinity ([NaCl] =0.01 and 0.51M) and temperature (295-333K).
The apparent diffusion coefficient (D_a) tended to be higher in the direction parallel than in the direction perpendicular to the orientation of the smectite particles. Higher salinity leads to an increase of the D_a-values for all conditions. The activation energies (ΔE_a) are independent of the orientation of the smectite particles. Higher dry densities correspond to higher ΔE_a-values. For a dry density of 1.0Mg/m³, the corresponding ΔE_a-value agrees well to a predicted value ΔE_a-value=24.66±0.96kJ/mol. This value is obtained as the difference of the activation energy for diffusion of cesium in pure water (16.47kJ/mol) and the Cs/Na ion exchange enthalpy ΔH⁰ (-11.10kJ/mol). For a dry density of 1.4Mg/m³, ΔE_a is 35.20±0.83kJ/mol. The higher ΔE_a-values found at higher dry densities are attributed to complex effects of ΔH⁰ and the lowering of porewater activity at high-dry densities.

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Clay barriers are important for the retardation of radionuclides in a high-level radioactive waste (HLW) repository and their performance has been analyzed based on an understanding of various processes, modeling and databases. Through the geochemical studies, we have developed models and databases for important processes, e.g., clay-water interaction and radionuclide sorption. The design for clay materials in the HLW repository has been based on an understanding of the long-term behavior of clay materials. Through the design studies, we have clarified many properties and processes of clay, e.g, extrusion/erosion into the fracture and gas migration.
This paper presents an overview of the important progress in clay performance and design and of difficulties encountered.

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The GESPER coupled geochemical reaction-mass transport analysis code was improved for application to complex regions, e.g. engineered barriers and the surrounding rock regions in radioactive waste disposal systems. To investigate the role of a bentonite buffer in systems with cementitious materials as a component, typical phenomena considered in the interaction of cement leaching water and a typical Japanese sodium-type bentonite were analyzed by code under various conditions. Bentonite calcification, calcite precipitation, and pH-dependent protonation of the edge sites of smectite were examined. Cation-exchange characteristics of the bentonite may maintain the expected performance of sodium-type bentonite under conditions of sodium concentration higher than about 0.01 M in the pore water. A bentonite buffer layer of 1 m thickness may reduce pH in the pore water for several hundred years. Phenomena in the bentonite and surrounding rock were calculated simultaneously using a multimedia model, to be discussed.

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Commercial exploitation of the oil sands in northern Alberta in the past 30 years has resulted in the accumulation of almost one billion cubic metres of a clay slurry known as mature fine tailings or MFT. Several technologies are available for the reclamation of the accumulated MFT, and several exist for the prevention of MFT formation. The commercialization of the consolidated tailings or CT process for MFT reclamation and the utilization of thickeners to prevent MFT formation have underscored the importance of understanding clay behaviour in optimizing these processes. This paper discusses the important clay properties that determine the performance of the CT and thickener processes, which are the first steps in the reclamation of the MFT. The variability in clay mineralogy and size distribution in the oil sands is an important factor in determining process performance, as is the process water chemistry. X-ray diffraction and surface-area determinations on the clays, and rheology measurements on the clay slurries, are some of the techniques that enable an understanding of the clay slurry properties that determine oil sands tailings behaviour.

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The reserve of conventional light crude oil in Canada has diminished in recent years and initiatives have been taken by the oil industry to use alternatives such as heavy oil and bitumen from oilsands. One of the problems encountered during oilsands processing is the presence of intractable organic matter strongly bound to certain minerals, usually clays. These solids provide sites for sorption and chemical fixation of heavy oil and bitumen during the extraction process and are also associated with loss of these materials during recovery.
From a process optimization standpoint, it is therefore of considerable interest to develop a better understanding of the interaction between clays and the organic matter types present in bitumen. The prime consideration in the present work is to probe and investigate the adsorption behaviour of SARA fractions from bitumen and heavy oil on kaolinite. Differences and similarities in adsorption of these heavy oil and bitumen fractions are discussed.

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Currently, there is an increasing trend for the petroleum refining industry to use oil sands bitumen and heavy oils as a crude source. Some of the problems associated with bitumen and heavy oil production can be attributed to the presence of clays having surfaces coated with strongly bound organic matter. Deposition of this organic rich mineral matter contributes to problems in both recovery and upgrading. Consequently, understanding the interaction between clays and organic matter is essential to the successful optimisation of heavy oil and bitumen production.
In this work we report results related to the adsorption of well-characterized pentane insoluble (PI) fractions from Athabasca oilsands bitumen on kaolinite. For comparison purposes we also examine the adsorption of PI separated from Venezuelan heavy oil, Saudi Arabian light crude oil and Chinese Daqing conventional crude oil. The unadsorbed organic matter is probed by complementary analytical techniques to determine the chemical nature of the absorbed material. The results point to selective adsorption of heteroatoms rich heavier components.

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Hydrophobic clay minerals create problems related to reservoir wettability and fouling during oil production and upgrading. In this work, the prime objective is to investigate the effect of clay particle size on the adsorption of a well-characterized pentane insoluble fraction (PI) from Athabasca oilsands bitumen by clay minerals. A commercial sample of illite is separated into three fractions with median diameters of 10.3, 1.61 and 0.21-μm. The maximum monolayer coverage of PI is calculated from adsorption isotherms determined for each substrate. Maximum monolayer adsorption (mg/g) of PI on illite increases with decreasing size of clay particles. The organic material remaining in the supernatant and adsorbed organic material are characterized by several complementary analytical techniques. Comparison of the compositions in each case shows that the adsorption process is selective for heavy polar molecules.

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Smectite clay has been shown to sorb aflatoxin B₁ (AfB₁) in animal feed and thereby reduce its toxic influence on animals and its entrance to the human food chain. In an effort to find effective adsorbents, 39 samples proposed to adsorb aflatoxin were analyzed and classified into four groups based on their properties: coefficient of linear extensibility (COLE), pH, cation exchange capacity (CEC), organic carbon, microbial content and x-ray diffraction (XRD) spacings. A subset of 20 bentonite samples from commercial sources and reference minerals from 6 US-states and 2 sites in Mexico was selected for sorption determinations. A 10-fold difference in sorption based on the Langmuir equation was observed. Yet clay properties were mostly clustered and it is not clear which properties influence this variation. The basal spacing of AfB₁ saturated smectites exhibited greater resistance to collapse on heating than untreated smectites indicating that AfB₁ entered the interlayer galleries of the smectites. After heating the mycotoxin-clay complex the desorbed mycotoxin was altered indicating a reaction of the molecules with the clay surface. The most effective sorbent smectite samples were from three US-states (MS, ID, TX).

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Clay mineralogical studies have been undertaken on the OMEX core KSGX40 (164cm long) recovered from the Galicia Muddy Deposit of the continental shelf off Ria de Vigo. The chronology for this work is supported by three AMS 14C datings based on mixed foraminifera. Datings were corrected for a marine reservoir effect of 400 years and converted to calendar ages. Mineralogical studies were carried out on the<2μm fraction of the sediments using X-ray diffraction. The studied core spans the past-5000 cal years BR This record show high detrital illite and kaolinite contents and low smectite and/or chlorite contents, compatible with expected mid-latitude temperate humid climate. Although significant quantitative variations in clay mineralogy is clearly expressed by the (kaolinite+smectite)/(illite+chlorite)(Kt+Sm/Il+Chl) ratio and by illite “crystallinity”. Higher values of Kt+Sm/Il+Chl ratio and illite “crystallinity”(indicating poor crystallinities) suggest the occurrence, during the last 5000-years, of several intervals of warmth, for instance the Roman Warm Period (-2500-1950 cal years BP) and the Medieval Warm Period (-1100 and 700 cal years BP), intercalating cyclic colder events, like the Ice Age Cold Epoch (-3300-2500 cal years BP) and the Little Ice Age (-500-150 cal years BP). This work shows the potential of clay minerals to identify weak-amplitude and short climatic changes in Galicia Muddy Deposit.

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Compacted bentonite is a potential candidate buffer material for use in high-level radioactive waste disposal. Although the physico-chemical properties for the compacted form are required to assure the safety function of the system, experimental evidence is quite limited. Electro-migration experiments using tetra-alkyl-ammonium cations having different hydrated ionic radii and osmotic pressure measurements were performed to receive information on the solid/liquid interface in pore water under non-destructive conditions of the highly compacted bentonite (Na-montmorillonite 99%). The results indicated the pore water was strongly influenced by the solid surface and may not be treated as common free water. The geochemical code MINEQL was significantly revised to model the solubility, diffusivity and sorption coefficient simultaneously under consolidated condition. Calculations showed good accordance with the experimental information and the validity of the revision of MINEQL was demonstrated.

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In current mine-based operations in the oil sands of northern Alberta, the production of a given volume of bitumen generates the equivalent volume of mature fine tailings (MFT), a mixture of water, fines, and residual organics. The clay mineralogy of the oil sand is thought to have a major influence on settling behaviour of MFT. In order to develop methods of handling the growing problem of oil sands tailings containment and reclamation, it is critical to understand the nature and role of the fine suspended clay particles.
Most studies have identified the major clay minerals in the oil sands to be kaolinite and illite. The reported bulk surface area is far larger, however, than would be possible through contributions from kaolinite and illite alone. More recent x-ray diffraction studies have reported a low degree of interstratified smectite in kaolinite and illite to account for the observed surface area. The present work applies transmission electron microscopy lattice fringe imaging, and electron diffraction to evaluate the fundamental particle size of the clay minerals. Our investigations show that the mean fundamental particle thicknesses of kaolinite and illite in the minus 2-μm fraction are less than 10nm, which would explain the large surface areas reported in the literature.

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This report focuses on identifying the important asbestos fiber-type (s) in the etiology of the asbestos-related cancer mesothelioma. In the last century all three of the commercial fiber typesgrunerite (amosite) asbestos, chrysotile asbestos and riebeckite (crocidolite) asbestos-were mined, milled and used to fabricate asbestos-containing products in South Africa. The cases are a consecutive series of occupational and environmental mesotheliomas referred to South Africa's National Institute for Occupational Health.
The authors recovered the inorganic particles from the lung parenchyma in 43 human mesothelioma cases and used analytical transmission electron microscopy to determine the types and concentrations of fibrous minerals present. The predominant, often the only asbestos fiber-type, found in the pulmonary tissues was riebeckite (crocidolite) asbestos. The highest concentration of riebeckite (crocidolite) asbestos found was 10, 500, 000 fibers per gram of dried lung tissue. The mean concentration was 0.27 million fibers per gram of dried lung tissue which is between 4 to 59-fold below the concentration of chrysotile asbestos in general population where asbestos is found without asbestos-related disease. The results are consistent with the epidemiological reports indicating mesothelioma can develop in individuals with exposures to riebeckite (crocidolite) asbestos described as brief and/or slight.

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The authors are involved with the development of mineral-based formulations preferentially using local mineral resources, required for complementary topical applications in spas and well-being clinics associated to hotels and other touristic resorts which have been and are still being installed in Porto Santo island, part of the Madeira archipelago. Therefore, they have investigated the relevant chemical and thermal properties of a special clay (bentonite), and of a special sand (biogenic carbonate sand), one and the other occurring in the island of Porto Santo, traditionally used for many years for facial masks and sand-bathing, respectively. Also, the relevant properties, either of a thermal mud produced in a fumarole (solfatara) field, in the island of Sao Miguel, Azores archipelago, or of a biogenic amorphous silica bearing diatomite that occurs in Rio Maior, Central Portugal. Formulations based on blends of the referred to mineral raw-materials after undergoing appropriate preparation, and intended to be used for topical applications complementary to the traditional treatments based on biogenic carbonate sand and clay (bentonite) presently carried out in the well-being clinics are herein described.

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The black shale-hosted ÚRKÚT Mn-mineralization is among the 10 largest deposits in the World. In this study optical and electron microscopy demonstrated the biological formation of Mn-Fe minerals in Mn-carbonate ores. The ED-XRF elemental content maps and SEM-EDX observation of the ores showed distribution of Mn, Fe, and Si banded layer structure whereas the Mg, Al, and K are randomly distributed, as well as to explain the role of microorganisms associated with Ca and P. In both samples abundant microorganisms were found in the dark brown and white layers. Optical micrographs of thin sections clearly showed various shapes of cellular materials, such as spherule, oval, and filamentous morphologies. SEM-EDX observation revealed Fe-rich and P-Ca components around microorganisms showing spherule, tubular, and filamentous cells. The present investigation strongly suggests that the Mn-Fe and Si minerals were associated with microorganisms as a biological organic product. The identity of the bacteria responsible for Mn mineral formation is unknown, but is tentatively assigned to Mn and Fe bacteria on the basis of morphology. The genesis of rocks and minerals have played a pivotal role in Toarcian age, and they may even have acted as life genetic system.

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The dissolution process of the roof tiles affected by crustose lichen Lecidea sp. grown on their surfaces was investigated by means of optical microscope, XRD, SEM and EPMA. Japanese sekishu roof tiles with mineral compositions of quartz >> mullite was selected in this study. The growth of crustose lichen is often observed widespread on the surface of old roof tiles (about 20 years old). The surfaces of sekishu roof tiles are coated by glaze (melted feldspar-like glass), hence difficult to be affected by normal chemical weathering. However, the decomposition effects of them coated by crustose lichen is possibly mainly due to the biological activities. In this study, the lichen-roof tile interfaces were observed in detail. From the optical and electron microscopic observations, while chemical erosion and physical destruction caused by lichen activities were clearly found on the interfaces, characteristic growth of secondary clays was not recognized on them. In addition, chemical composition images obtained from EPMA do not indicate any leached or precipitated layer as protective weathering crust. From the overall observations it can be concluded that the dissolution progress of the surface of the sekishu roof tiles caused by crustose lichen continues without rate-decrease.

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The interaction between clays and microbes was investigated from field on pumice and imogolite in volcanic ash soils collected from Kurayoshi Pumice in Tottori, Japan. In comparison to laboratory studies on microbial films of cultures derived from fresh water system were examined. Observation of DAPI stained films revealed that numerous microbes have found in the system. Optical and electron microscopic observations of microbes showed that the imogolite films encrusted with areas of the bacterial cells. XRD of the films showed a 1.4, 0.82, 0.55, and 0.33 nm d-spacing consistent with a imogolite (OH) ₃Al₂O₃SiOH. EDX analysis revealed that the films were mainly composed of Al, Si, and Fe elements. FT-IR analysis exhibited the characteristic adsorption bands of clays for O-H (3400cm^-1), H-O-H (1650cm^-1) and Si-O-Al (1000 and 950cm^-1) and organic materials for C-H-COOH (3000 cm^-1) and CNH (1200 and 1500 cm^-1). The imogolite films contain higher concentration of nitrogen (0.08wt%), carbon (2.20wt%), and sulfur (0.11wt%) than that of pumice in the same volcanic ash soils, suggesting that the imogolite was closely associated with adhesive organics. Scanning electron microscopy (SEM) showed a variety of bacterial-like forms both in the natural volcanic ash soils and cultured water system. Transmission electron microscopy (TEM) revealed extensively mineralized bacterial cells with fibrous network structure of imogolite formed on both coccus and bacillus type bacterial cells, showing electron diffraction pattern of a diffuse halo at the initial stage. The well-developed bio-films show lattice images of dehydrated imogolite with 1.0-1.1nm d-spacings. The present investigation strongly suggests that imogolite was interacted with bacterial cohesion as a bio-organic clay product. The identity of the bacteria responsible for bio-imogolite formation is unknown, but microorganisms living in the films make an important role as a nucleation site for the formation of imogolite in volcanic ash soils. The bio-imogolite may have been formed from biochemical weathering products of cohesive materials, which subsequently controlled the formation of clay-organic complexes.

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Allophanic soils exhibit higher organic carbon and nitrogen content than the one measured in other clayey soils. So, there is a need to understand the links between the sequestration mechanism of C and N in these soils, and other soil physical parameters. Allophanes aggregates have physical features very close to that of synthetic gels, a fractal geometry, a bulk density close to 0.5g/cm³ and develop a high specific surface area. Moreover, allophanic soils behave as gels upon drying and exhibit an important irreversible shrinkage which affects the soil physical features. Because of this analogy between allophanes and synthetic gels we propose to control the drying step by CO₂ supercritical drying procedure (SD) and we present new results on the preservation of the porous features of allophanic soils by SD. The textural properties such as specific surface area and mean pore size are systematically higher for the supercritical dried samples compared to the classical dried samples, indicating the preserving effect of the SD which shows the interest of this drying method to this natural and complex “gels”. We also discuss the C and N content of these soils and possible correlation with the pore volume features measured after SD. We thus show the clear effect of the true specific surface area on the C and N content of the allophanic soils.

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Allophane appears as aggregates of unit particles of hollow sphere (nano-ball) with diameter of 3.5 to 5.0nm. The wall has some pores which accommodate water molecules. Water vapor adsorption on two natural nano-ball allophane samples was examined under different relative humidities (RHs). The adsorption isotherm up to RH of 0.51 fitted to Langmuir equation, but at higher RHs the curve diverged due to capillary condensation. By using data up to RH of 0.51 and allophane unit particle model of 4.3nm in diameter and molecular weight of 46510, the Langmuir maximum adsorption was calculated as 1240-1290 water molecules per unit particle for the two samples. The allophane model has various functional groups such as AlOHAl (outer surface), SiOH (inner surface), AlOH2 (pore), Si (OH) 2 (pore) and AlOSi (pore), and total numbers of the functional groups become 1044 per allophane unit particle. These indicate that, under lower RHs, water molecules are mainly adsorbed on the functional groups through hydrogen bonding. Molecular orbital calculation (MOPAC PM3) indicated that adsorption affinity of water molecule was higher for SiOH than for AlOHAl, and that charge values on O and H atoms of the functional groups mainly governed hydrogen bond formation with the water molecules.

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Nano-ball allophane is hydrous aluminum silicate of hollow spherical morphology with diameter of 3. 5 to 5.0nm, but its chemical structure has not been clarified completely. An electron microscopic observation showed that allophane aggregate was composed of unit particles with uniform size. It must be considered that allophane has definite structural arrangement and therefore can not be considered as ‘amorphous’. We found that regularity of polyhedron could be used to build up basic structure of nano-ball allophane. This polyhedron is composed of eight hexagonal gibbsite sheets with orthosilicic acid bonded to it. The bond lengths of Al-O and Si-O are 0.192 and 0.162nm. The molecular weight is 46510 and Si/Al atomic ratio is 0.574. The model has a diameter of 4.25nm and contains six holes. By using calculated specific gravity of 2.75g cm^-3, diameter of 4.25nm and wall thickness of 0.7nm, the amount of water retention in the space within the wall and specific surface area were calculated as 0.16% and 1114m² g^-1. These calculation results are in good agreement with experimental data, and confirm that our proposed model is the chemical structure of nano-ball allophane in the natural environment.

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To study the interaction of uranium with HAS (hydroxyl aluminum silicate) in a solution, HAS was synthesized from the mixture of four solutions (25ml of 0.1M hydrochloric acid solutions, 40ml of 20mM aluminum chloride, 25ml of 20ppm uranium nitrate and 40ml of 20mM sodium orthosilicate) and 370ml of distilled water at the pH between 3.6 and 6.0. The XRD and FTIR analysis of solid products showed that the product was amorphous HAS. Analysis of the solutions filtered with four kinds of filters (5nm, 25nm, 100nm, 450nm) showed that HAS colloids containing uranium were formed between pH 4.3 and pH 5.4 and that the particle sizes of the HAS colloids are between 100nm and 450nm. At pH 5.6, the HAS colloids floating in the solution aggregate to large particles and precipitate; more than 99% of Al and U were depleted from the solution, and 72% of Si was depleted. This indicates that uranium co-precipitate with HAS. One of the possible mechanism of the co-precipitation is that the amount of uranyl-hydroxyl carbonate ion having negative charge increased with increasing pH, and this uranyl-hydroxyl carbonate anion was absorbed on HAS cation, thus uranium hydroxide precipitated with HAS.

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Typical noncrystalline and poorly crystalline materials in soils are allophane, imogolite, ferrihydrite and humus. These materials occur in Andisols and spodic horizons in relatively high amounts. The humus is complexed with Al in these soils and the humus-Al complex shows high resistance to decomposition. Chemical characteristics of the soils with these materials are variable charge, high phosphate fixation and so on. The variable charge sites show high preference to multivalent cations. Although silicon and some alkaline and alkaline-earth elements are removed, many heavy metals are retained in Andisols during formation of the Al and Fe-rich variable charge materials. These characteristics were problems for crop production but they were mostly amended by high input of fertilizers. Physical characteristics of the soils with these inorganic and organic materials stem from stable aggregates and porous structure, leading to low bulk density, high water retention, high water and air permeability. These physical characteristics are suitable for upland crop production. Allophane and imogolite are natural nano-porous materials expected also for industrial uses such as humidity control, dewing control and heat exchange at the temperature lower than 373 K.

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