Phosphate adsorption behavior of vermiculite (Vt) complexed with hydroxyaluminum (HyA) and hydroxyaluminosilicate (HAS) ions were studied at equilibrating solution pH-5.0. The HAS ions were prepared from solutions containing HyA ions andorthosilicic acids at an Al concentration of-4mM; Si/Al atomic ratios of 0, 0.25, 0.50, and 1.0; NaOH/Al molar ratios of 1.0, 2.0, and 2.5. At initial P concentration of 0.25 to 50mM, the adsorption of phosphate by these complexes decreased with increase in the NaOH/Al and Si/Al ratios of hydroxy materials fixed on Vt. When adsorption data were evaluated using the Scatchard plots of Langmuir equation, multiple linear relationships were observed which suggested the presence of multiple population of adsorption sites that have a differing affinity for phosphate ions. Both adsorption maxima and binding energy for the adsorption sites in the higher (region I) and lower (region II) affinity regions of different complexes were in decreasing trends with increasing NaOH/Al and Si/Al ratios of the fixed ions. The total phosphate adsorption maxima of different complexes ranged from 0.40 to 0.96mmole g^-1in comparison to only 0.17mmole g^-1as found for untreated Vt. Ligand exchange reactions in which phosphate ions displaced OH or OH₂ groups from coordination shells of structural Al on the edges of Vt and HyA or HAS polymers fixed on external planar surfaces and/or interlamellar spaces of Vt may be involved in the phosphate adsorption processes in region I. In region II, phosphate adsorption may be occurred through ligand exchange predominantly with OH groups linking Al atoms inside the polymeric structure of the fixed HyA or HAS ions. In the HAS-Vt complexes, upon phosphate adsorption, the resultant HAS-phosphate complexes weresubstantially to almost entirely expelled from the interlamellar spaces of Vt. While, only a partial expulsion of the interlayer HyA-phosphate complexes was noticed following phosphate adsorption by the HyA-Vt complexes. Very high phosphate adsorption capacities of the complexes as evaluated in the present study merit attention in Pfertility management in acidic and nonallophanic Andisols and related soils.

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Hydroxy-interlayered vermiculite (Vt) and montmorillonite (Mt) clays wereprepared in the laboratory through reacting<2μm sized Vt and Mt clays with hydroxyaluminum (HyA) and hydroxyaluminosilicate (HAS) ionic solutions having final Al concentrations of around 4 mM; OH/Al molar ratios of 1.0, 2.0, and 2.5; and Si/Al atomic ratios of around 0.00, 0.25, 0.50, and 1.00. After reaction, varying extents of Al and Si fixation on Vt and Mt clays were recorded due to different Si/Al and OH/Al ratios of the reacting HyA and HAS ionic solutions suggesting different degrees of interlayer filling with hydroxy-materials in the resultant HyA/HAS-Vt/Mt complexes. Ammonium fixation and exchange capacities of these HyA/HAS (OH/Al=1.0, 2.0, and 2.5)-Vt and HyA/HAS (OH/Al=2.0)-Mt complexes were studied in comparison to untreated Vt and Mt with added NH4 at different rates ranging from around 20 to 300 meq/100g. Untreated Vt clay showed NH₄fixation as high as 91 meq/100 g in contrast to only 16 meq/100g exchangeable NH4. A maximum of 14 meq NH₄/100g was fixed by untreated Mt in comparison to its 60 meq/100 g total NH₄adsorption ability. In HyA/HAS-Vt complexes, NH₄fixation reduced drastically and ranged from 10 to 30 meq/100g in comparison to their total NH4 adsorption abilities ranging from 62 to 83 meq/100g in different cases. Fixation of NH4 by HyA/HAS-Mt complexes ranged from only 2 to 4 meq/100 g suggesting almost elimination of the fixation capacities. Ammonium became more exchangeable due to the presence of hydroxy-interlayers in the clays. The reduction in CEC and well known propping effects of hydroxy-cation islands in the interlayer spaces of Vt and Mt might have hindered NH4 fixation by the complexes. The relationships of maximum NH₄fixing abilities of the HyA/HAS-Vt complexes with the amounts of Al, Si, and Al + Si fixed on Vt were all exponential and negative. However, the amount of either Al or Al+Si fixed on Vt appeared as equally good indicators of NH₄fixing capacities of hydroxy-interlayered Vt clay. The relationships between ammonium and potassium fixing capacities of these complexes involving both Vt and Mt clays as found for different levels of added NH₄and K were all significantly linear and positive.

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Smectites separated from three soils of Ganges Floodplain, Bangladesh, were characterized. The smectites content in the fine clay fractions was in a range of 62 and 88%. Expansion to 1.8 nm by the Greene-Kelly test and the (060) spacingaround 0.150 nm suggested that the smectites were mainly beidellite-type. Elemental composition calculated from total chemical analysis showed that the smectites had layer-charge of tetrahedral-origin and were rich in Fe. The structural formula for the smectites of Silty Ganges Alluvium, which is hardly subjected to decalcification, was estimated as (Si_6.90Al1.10)(Al_2.46Fe_0.99Mg0.76) O₂₀ (OH) ₄X_1.25. The impact of iron-rich beidellite on the soil fertility potential was discussed.

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Mineralogical and chemical examinations on interstratified illite/smectite (I/S) from the Koyoshigawaoki well in the Akita basin provide an excellent example to document the diagenetic change of smectite to illite.
X-ray diffraction analysis shows a stepwise increase in percentage of illite layer with depth: two abrupt increases in illite layers are recognized at depths just below 2, 500m and at a depth interval between 3, 800 and 4, 500m. In addition, conversion of random (R=0) I/S into R=1 ordered I/S records at depths of between 3, 800 and 4, 000m, which is compatible with a Tmax value of 435°C by Rock-Eval pyrolysis. Present geothermal gradient from temperature data, however, indicates that the conversion is likely to occur at a depth of 3, 000m. This discrepancy may be explained by a reverse fault at a depth of 2, 470m which resulted in a deeper burial of sediments up to 1, 000m. Deeply buried materials such as I/S and organic matter have not yet attained an equilibrium condition that corresponds to thepresent geothermal gradient. As a result, the rapid increase in percentage of illite layer below 2, 500m may be a discontinuity caused by the reverse fault. Anotherrapid variation in layer proportion between 3, 800 and 4, 500m is attributable toneoformation of R=1 ordered I/S.
Chemical analysis also illustrates a remarkable compositional variation in I/S with burial depth, demonstrating an increase in potassium and aluminum and adecrease in silica. This is expressed by the following reaction: smectite+Al³⁺+K⁺→illite+Si⁴⁺
In this reaction, potassium is derived from K-feldspar, which is present in significant amounts throughout the well.

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Intercalation of a crown ether (1 8-crown-6) into layered silicates was investigated. Intercalation compounds with the basal spacings of ca. 1.9nm were obtained by the solid-state reactions between K-, Rb-, and NH₄-montmorillonitesand 18-crown-6, while the basal spacings of the products were different (1.4, 1.5, and 1.5 nm for K-, Rb-, and NH₄-montmorillonites, respectively) when a methanolic solution of 18-crown-6 was employed. 18-crown-6 was intercalated into theinterlayer space of non swelling K-fluor-tetrasilicic mica probably due to the strong interactions between interlayer cations and 18-crown-6. The reaction between Kkenyaite and 18-crown-6 gave an intercalation compound with the basal spacing of ca. 3.0nm. It has been proved that the reactions between the layered silicates and 18-crown-6 without solvents are novel synthetic ways to lead intercalationcompounds.

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