Changing some experimental techniques, the DTA analysis of a kaolinite containing clay shows significant exothermic behaviors. The regions of so called 1^st and 2^nd exotherms resolve into more peaks.I n the high temperature region, mullitization peaks become much pronounced in comparison to low intensity of 2^nd exotherm noted usually in earlier literature. In total, Bhandak kaolinite exhibits three endotherms and five exotherms.

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This work examines the adsorptivity of different combinations of lead, copper and cadmium ions onto the clay mineral kaolinite covering a wide range of concentrations of single, binary and ternary solutions. Batch adsorption equilibrium tests were used. The results of single Pb²⁺, Cu²⁺ and Cd²⁺ solutions were compared with those of binary Pb²⁺Cu^2+, Pb²⁺Cd²⁺, Cu²⁺Cd²⁺ and ternary Pb²⁺Cu²⁺Cd²⁺ solutions. Results indicate that the adsorptivity of heavy metal ions is slightly lower in binary and ternary solutions than for single ion species in the solution. Lead shows a higher selectivity on kaolinite of the three heavy metal ions, while Cu²⁺ and Cd²⁺ give very similar s

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We obtained concentrated solutions of hydroxyaluminum silicate (HAS) ions by instantaneously mixing aluminum chloride solution and sodium orthosilicate solutions with different concentrations of NaOH. The Si/A1 molar ratio of the HAS ions purified by dialysis was in a narrow range from 0.35 to 0.39 irrespective of the NaOH/Al ratio. Heating the HAS solutions at near boiling point gave allophane and small amount of imogolite as well dispersed sol. On the other hand, heating HAS solutions after dialysis yielded boehmite as precipitate and allophane as well dispersed sol, but gave no detectable amount of imogolite although there was little chloride ion disturbing development of imogolite structure. These experimental results showed that the Si/A1 molar ratio of HAS ion is significantly lower than that of imogolite and free monosilicic acid is incorporated during development of imogolite tubes. This suggests that better imogolite yield will be achieved by addition of monosilicic a cid to the dialyzed HASsolutions before heat treatment or by removal of chloride ion during heating.

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A clay-titanium oxide nanocomposite was synthesized from smectite powder and titanium oxide powder by dispersing them in water followed by centrifuge sedimentation. Heated products were obtained by treating the mixed gel hydrothermally in an autoclave. The XRD patterns of the unheated and heated products showed basal plane reflections in the range of 8.5-9.4 nm suggesting formation of composites having monolayers of the titanium oxide particles between smectite layers. Their layer spacing and pore size got enlarged after the hydrothermal treatment suggesting a crystal growth of the titanium oxide particles. The composite well adsorbed As (III) and As (V) dissolved in water. An application of this composite as an additive for buffer layers in waste landfill sites was examined.

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The absolute values of zeta (ζ) potentials estimated by an electrokinetics sonic amplitude (ESA) method decreased gradually with the increase of NaCl concentration below the flocculation value of 1.5×10^-2 and 1.5×10^-3 mol L^-1 in the suspension of montmorillonite at pH 8 and allophane at pH 7.5 respectively. Theζ potentials increased inversely above the flocculation values. The absolute value of potential in kaolinite suspension at pH 6 was found to decrease even above its flocculation value, and increased inversely above 5.6×10^-3 mol L^-1 NaCl. The flocs already began to form below the fl occulation value in the montmorillonite suspension at pH 8, but the formation and precipitation of the fl ocs began almost simultaneously in the kaolinite suspension at pH 6. Theζ potential of allophane at pH 3.5 began to increase at about 1.5×10^-3 mol L^-1 NaC1, which coincided with the absolute value at pH 7.5. The flocs in the allophane suspension at pH 3.5 began to form at near 2×10^-3 mol L^-1 NaC1, but to precipitate above 5×10^-3 mol L^-1 NaCl. The aspects of flocs formation in allophane were a little different from montmorillonite and kaolinite.

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We developed a simple method to measure carbonate adsorption by soils and clays at equilibrium with the air having elevated carbon dioxide concentrations. The method uses bags made of laminated polyamide-polyethylene film as experimental container. Soil or clay sample is put in the bag and sealed up. Addition of equilibrating solution and air containing CO² and sampling of the air and solution are all made through a three-way stopcock attached to the bag. The equilibrium pH is measured with a fow-through glass electrode attached also to the stopcock.
The carbonate adsorption by specimen boehmite was measured with the proposed method under equilibrium CO² concentration of 3 to 3.9% and pH of 4.4 to 7.6. The carbonate adsorption increased as the pH increased, reached maximum at around pH 7.4 and then decreased. The coefficient of variation of the measured values ranged 2.0 to 4.3%, which were significantly lower than those from measurements with conventional methods.

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