The uptake behavior of anionic chelating agents into the magnesium-aluminium oxide precursor, Mg_0.58Al_0.28_??__0.14O (_??_: vacancy), prepared by the thermal decomposition of a synthetic Mg-Al carbonated layered double hydroxide, Mg_0.67Al_0.33 (OH) ₂ (CO₃) _0.16·0.46 H₂O, was investigated at 25°C. The oxide solid solution was found to include highly the chelating agents such as ethylenediaminetetraacetate, its metal complexes, nitrilotriacetate and other similar anions as guest anion instead of CO^2-₃ ion from aqueous solutions with reconstructing the original hydrotalcite-like layer structure. The effect of initial solute concentration on the uptake was studied and isotherm parameters were evaluated. The Freundlich adsorption isotherm was found to be more suitable for all systems tested here and the values of the parameters, k and n, were quite higher. On the basis of the data, the relationship between the isotherm parameters and the number of negative charge, structure and arrangement of these anions in the interlayer of the resulting hydrotalcite-like compound was also discussed.

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It has been found that initial grinding of starting materials is effective in promoting reactivity in the synthesis of kaolinite. A mixture of amorphous silica and aluminum hydroxide with a Si/Al atomic ratio of 1.0 was ground and then used as the starting material for hydrothermal synthesis. The starting material was placed in a Teflon reaction vessel together with distilled water, and kept at 220°C. The characterization of the starting materials and products was carried out with XRD, IR, DTA-TG, ²⁹Si-and ₂₇A1-MAS/NMR, and TEM. The starting material which had been ground for 200 h was an amorphous aluminosilicate with four-and six-coordinated Al. Kaolinite could be obtained from this well-ground starting material in a relatively short reaction time in comparison to mixtures not subjected to the pre-grinding process. In the latter case, bayerite was changed into bohmite, and was then converted to well crystallized kaolinite with euhedral morphology of the hexagonal plate. The differences in the local structures of the starting material around the Si, Al atoms, and OH groups, which had been brought about by the mechanochemical reaction during the grinding, are likely to have an influence on formation of kaolinite.

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Phillipsite was synthesized from the silica-poor fly ash by the hydrothermal treatment with 2N-NaOH solution at 105°C. Most of phillipsite was synthesized between 2 hrs. and 6 hrs. in the reaction time. The phillipsite synthesis mainly depended on the Al concentration of the liquid phase, and was taken place from the dissolution of the silicate glass and the amorphous Al compound. The cation exchange capacity (CEC) of the synthesized phillipsite was 198 meq/100g. The suggested process of phillipsite synthesis was (1) the dissolution of amorphous materials and condensed compounds of fly ash, (2) the dissolution of the sphere matrix of fly ash particles, (3) the supersaturation of liquid phase, (4) the phillipsite formation, and (5) the growth of phillipsite crystal.

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The physico-chemical properties of the phillipsite derived from fly ash were investigated to evaluate the utility of the product in the various fields of industry and agriculture. CEC of the product was little affected by the suspension pH, and varied with the exchange cations in the following sequence: NH⁺₄>K⁺>Ca²⁺. A rapid ion exchange reaction took place on the surface of the product. The synthesized phillipsite was stable below 250°C or above pH 3. The hypothetical chemical formula of the synthesized phillipsite would be suggested as follows: K_0.14 Na_0.86 (AlSi_1.84 O_5.68)·nH₂O. The proportion of the synthesized phillipsite in the product was estimated to be about 33.6%. It was considered that the product can be used for treating the poultry wastewater.

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