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Novel Synthesis of Pure Leucite from an Aluminosolicate Precursor

X-ray amorphous K-aluminosilicate gel (x1Na2O, x2K2O)• Al2O3• ySiO2• zH2O) was prepared by the exchange of the original (sodium) ions from Na-aluminosilicate with silicate and aluminate solutions in the ratio of Si/Al~1 . The thermal treatment of K-exchanged aluminosilicate was carried out by isothermal heating for 3 h at the temperature that corresponded to the temperature of the exothermal peak in DSC curve of the sample. The starting material and the product of the solid-state, high-temperature transformation were analyzed/characterized by different methods such as X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), differential thermal analysis (DTA), differential scanning calorimetry (DSC), infrared spectroscopy (FT-IR) and nitrogen absorption (BET method). Thermal treatment of the gel (isothermal heating at 1423 K for 3 h) resulted in its transformation into a crystalline aluminosilicate phase having chemical composition of KAlSi2O6. The transformation was accompanied by a drastic decrease in BET specific surface area caused by the transition of (micro/meso)-porous amorphous K-aluminosilicate into a more dense, non-porous crystalline phase of tetragonal leucite.

synthesis; leucite; aluminosilicate precursor; thermal treatment

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