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Influence of Alkali Cations (Me = Li, Na, K, Rb, Cs) on Physico-chemical Properties of the Liquid and Solid Phases of Me-aluminosilicate Hydrogels

Me-aluminosilicate hydrogels having the bath molar oxide composition xMe2O• Al2O3• ySiO2• zH2O (Me = Li, Na, K, Rb and Cs ; x = 4.24 – 4.66, y = 2.49 and z = 334.53 – 344.48 for the hydrogels of the run series a, and x = 9.52 – 10.30, y = 7.91 – 7.95 and z = 1073.38 – 1097.29 for the hydrogels of the run series b), were prepared by mixing together the appropriate Me-silicate and Me-aluminate solutions at ambient temperature. After ageing at 25o C for 48 h, and solid-liquid separation (by centrifugation), chemical compositions (contents of Me2O, Al2O3 and SiO2) of the liquid and solid phases were determined by atomic absorption spectroscopy (AAS), and the solid phases were additionally analyzed/characterized by X-ray diffractiometry (XRD), Fourier transform infrared spectroscopy (FTIR) and differential thermogravimerty (DTG). Specific equilibrium distributions of Me2O, Al2O3 and SiO2 between the truly amorphous solid phase and the liquid phase were discussed in the terms of: (a) influence of Me ions on distribution of different silicate species and their degrees of hydroxylation in the starting Me-silicate solutions and (b) influence of the degrees of hydroxylation of silicate species in the starting Me-silicate solutions on the polycondensation reactions with monomeric Al(OH)4- anions during the formation of aluminosilicate gel skeleton. The presence/absence of the formation of zeolite-like structures (“ quasi-crystalline” ) in the gel matrix was discussed in the terms of the “ structure-forming” nature of Li+ and Na+ ions and the “ structure-breaking” character of K+, Rb+ and Cs+ ions.

Alkaline cations ; Aluminosilicate hydrogels ; Physico-chemical properties ; Solid phase ; Liquid phase

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