Layered double hydroxides (LDHs) are the well known class of lamellar compounds with anion exchange ability. In this study, Mg-Al-CI LDH was complexed to siliceous porous carriers in order to develop a practical adsorbent for anionic dyes. First, the carrier granule such as synthetic silica gel or natural cristobalite rock was added into the mixed aqueous solution of MgCl₂ and AlCl₃ to impregnate both metal ions in the pores of the carrier and then the resulting suspension was poured slowly to a NaOH solution at 60°C and pH 10 with agitation. A large portion of the LDH, Mg_1-xAl_x (OH) ₂Cl_x·yH₂O (x=0.21-0.22, y=0.59-0.78), was found to form in the pores of the carrier. From the anion exchange experiment using Orange II, the composite materials exhibited the high exchange ability and theability based on LDH unit weight became as follows: LDH/ silica gel (pore size 70Å)>LDH/cristobalite rock (pore size 198Å)>LDH. Thus the more LDH was dispersed finely to the carrier, the more exchange ability for anionic dye was enhanced.

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Mixed-layer kaolinite/smectite minerals constitute the principal clay assemblage in the Quaternary alluvium type red-burning clay resource in Liloan, Cebu, Philippines, based on analytical testworks employing x-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetry (TG), infrared (IR) absorption spectroscopy, scanning electron microscopy (SEM), and energy dispersive x-ray (EDX) performed on several clay samples obtained from the area. Careful examination of diffraction curves indicate that the main constituent mineral is randomly interstratified kaolinite/smectite. Computer-simulated x-ray diffractograms of the mixed-layer kaolinite/smectite show good agreement with the observed x-ray diagrams in (001) and (002) basal reflections. Calculated values derived from simulation, moreover, illustrate the ratio of kaolinite to smectite to be generally higher at surface horizon but gradually becomes of almost equal proportion at depth. The slight variability in ratio may be linked to the effect or degree of differential weathering. Quartz and feldspar are ubiquitous accessory minerals detected in the non-clay fraction.

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Dissolution kinetics of phlogopite were studied at 50°, 80° and 120°C using 20ml and 100ml of 0.01 N HCl solutions containing 0.1 M NaCl (pH 1.9). The residual solid materials showed the formation of many etch pits and leached layers. The etch pits are formed more easily on the side surfaces than on the cleavage surfaces of phlogopite. The leached layer which was formed around of the flakes is composed of vermiculite and interstratified mica/vermiculite. These reveal that the dissolution of phlogopite crystal proceeds anisotropically and the dissolution rate is relatively greater along the a and b axis directions than along the c axis direction.
The release rates of cations other than Si from phlogopite are explained by a diffusion kinetic equation based on a contracting disk model. The Si release, which is controlled by a surface reaction mechanism, is much slower than the other cations, and is a rate-limiting process of the entire dissolution of phlogopite. The dissolution rates of phlogopite depend on water/solid ratios used in this experiment, and were about six times faster in the 100ml experiments than in the 20ml experiments.
The degree of incongruency of dissolution was also more significant in the 100 ml experiments than in the 20ml experiments. The calculated activation energies for release of cations in the 100 ml experiments, followed the order, Si>Fe, Mg, Al>K, which could be related to the priority of release of cations from phlogopite structure. The activation energiesfor the cations other than Si (45-55 kJ/mol) were higher than those reported previously for a diffusion process of cations from phyllosilicates into solution (-40 kJ/mol). This is probably due to the existence of vermiculite and interstratified mica/vermiculite which acts as a diffusion-inhibiting layer.

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Intercalation of ε-caprolactam into kaolinite was achieved by the guest displacementmethod using a kaolinite-methanol intercalation compound as the intermediate. The basal spacing of the kaolinite-ε-caprolactam intercalation compound was 1.31 nm, which was larger than those of both kaolinite (0.72 nm) and the kaolinite-methanol intercalation compound (1.11 nm). IR analysis revealed the formation of hydrogen bondings between the carbonyl groups of ε-caprolactam and the hydroxyl groups of kaolinite. The thermal behavior of the product implied that in-situ polymerization of ε-caprolactam to nylon 6 by heat treatment was unsuccessful because of deintercalation reaction of ε-caprolactam molecules.

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Aluminol groups such as Al-OH or Al-OH₂ are shown to have an important role in adsorbing low molecular organic compounds, acetic, oxalic and citric acid, on nano-ball allophane samples. The amount of the three organic compounds adsorbed was higher for KyP sample with Si/Al=0.67 than KnP sample with Si/Al=0.99 due to much more aluminol content of the KyP sample. Langmuir and Freundlich adsorption equations were used to describe the adsorption of the organic compounds. At lower pH, the amount of organic compounds adsorbed by nano-ball was as follow: oxalate>citrate>acetate, and at higher pH, citrate>oxalate>acetate. For all cases, the Langmuir and Freundlich parameters tended to decrease with increasing solution pH. Adsorption of acetate by allophane at pH 4-6 fitted with Langmuir model and at pH 8-10 fitted with Freundlich model. For adsorption of oxalate, only at pH 4 suited with the Langmuir model. All the adsorption data of citrate fitted with the Freundlich model. From the observed changes in solution pH with adsorption, reaction mechanism between the three organic compounds and allophane was proposed as follow: a) Deprotonation (release of H+), this was reaction between acetate or citrate and allophane at low pH; b) Dehydroxylation (release of OH-), this was reaction between acetate or citrate and allophane at high pH and reaction of oxalate. At lower pH, Al was easier to be released than Si from KyP, but at highe pH, Si was easier to be released than Al. For KnP, release of Si was much more than Al at all pHs, because the KnP sample contains a lot of condensed Si tetrahedra which is bonded weakly on the fundamental allophane structure.

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Gas adsorption properties of microporous silica prepared by selective leaching of metakaolinite were investigated at 25 °C using various adsorbates of different molecular size, shape and polarity, i.e. water, methanol, butan-l-ol, cyclohexane and 2, 2, 4-trimethylpentane. The microporous silica was obtained by chemical treatment of metakaolinite, (derived from the 1: 1 layered clay mineral kaolinite (Al₂ (OH) ₄Si₂ O₅) by firing at 600 °C for 24 h) with a 20 mass% H₂SO₄ solution at 90 °C for 2 h with stirring. The pore size of 0.6 nm previously obtained from the t-plot and Horvath-Kawazoe (HK) methods was examined by comparison of the results obtained from the adsorption isotherms of 2, 2, 4-trimethylpentane on zeolite 4A (pore size 0.42 nm), zeolite ZSM-5 (0.54 nm) and mordenite (0.67 nm). The pore size of the microporous silica was found to be between those of ZSM-5 and mordenite, in good agreement with the value derived from the t-plot and HK methods. The adsorption isotherms of all adsorbates showed a convex curve in the low partial pressure (P/P₀) range irrespective of the polarity of adsorbates, indicating micropore filling due to strong interaction between adsorbate and adsorbent in micropores. The increase of adsorption in the low P/N range (P/P₀ < 0.05) changed with the shape, size and polarity of the adsorbates due to the steric hindrance and chemical affinity of the adsorbates.

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Soils of Bangladesh have been formed from different kinds of parent materials and are spread over three major physiographic units: hills, terraces and floodplains. Clay mineral data were scarce till eighties, later, sporadically some works were done at both home and abroad. The available clay mineralogical data have been compiled and summarized for making a clay mineralogical map on the national basis. Mica was the predominant clay mineral in almost all the soils. Other major minerals were smectite (mainly iron-rich high-charge beidellite), chlorite, vermiculite, kaolinite, and interstratified mica-chlorite, mica-vermiculite-smectite and kaolinite-smectite, depending on the physiographic location of the soils. The proposed clay mineralogical map has eight mapping units: namely, Mc-Ch*, Mc-St, Mc-Vt*-Kt, Mc-Ch-Vt*, Mc-Mx-Kt, Kt-Mc, Mc-Kt-Vt* and Mc-Kt-Vt, where the symbols Mc, Ch, St, Vt, Kt, and Mx indicate mica, chlorite, smectite, vermiculite, kaolinite, and mixedlayer minerals, respectively, and asterisk (*) means partial chloritization of some vermiculite or partial degradation of some chlorite. This generalized clay mineralogical map well corresponded with the agroecological regions of Bangladesh.

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The mineral composition of the soil clay fractions in natural levee and back slough of Takeda River, Fukui Prefecture, Central Japan was estimated by the method using X-ray diffraction and thermogravimetry after Kitagawa et al.(1994). The results was summarized as follows:
Kaolin minerals, chlorite, mica minerals, chlorite-vermiculite intergrade, vermiculite, smectite and amorphous materials were detected in each horizon of the soils. It was suggested that these minerals originated mainly in the materials transported from the upper stream of the river. Moreover, the contents of clay minerals were not different between the natural levee soils and the back sloughones. This result was different from the conclusion in the meander belt of alluvial plains in Northeast Japan after Saegusa (1979), in which chlorite and kaolinite are dominant in the soils of natural levee while smectite is dominant in those of back slough. Thisshould be due to the regional difference or the scale of alluvial plain.

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