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Physical chemisry of aluminosilicate gels : part 3. Influence of the batch alkalinity on the chemical composition of the gels

The influence of the batch molar ratio YbN = [SiO2]bN/[Al2O3bN [the subscript bN denotes different batches b ( = 1, 2, 3 and 4) of different systems N (= I, II, III and IV)] and alkalinity of systems on the distribution of Na, Al and Si between the solid (S) and the liquid (L) phase of the sodium aluminosilicate hydrogels prepared at different batch concentrations [Al2O3]bN and different batch alkalinities defined by the molar ratios, a = [Na2O/Al2O3o (molar ratio Na2O/Al2O3 in the starting aluminate solution) and b = [Na2O/SiO2]o (molar ratio Na2O/SiO2 in the starting silicate solution) were investigated by measuring the concentrations of Na , Al and Si in both the solid(S) and liquid(L) phase by atomic absorption spectroscopy. Analysis of the experimental results have shown that: (i) [Na2O]S = [Al2O3]S = 0.0631 - 0.0638 AN - (0.216 AN - 0.228)/([Na2O]bNYbN),(ii) YS = 5.925 - 0.335 AN - (6.575 - 0.415 AN)/YbN and (iii) ln YL[Al2O3]S = 9.8 - (32 - 2.3 AN)/YbN , where, YS = [SiO2]S/[Al2O3]S, YL = [SiO2]L/[Al2O3]L and AN = aN + bN. Based on these relationships, it was found that the equation: 32 - 2.3 A) YS + (0.415 A - 6.575) ln YL + 20.2605 A - 0.7705 A2 = 125.17 satisfactorily describes the equilibrium distribution of Na2O, Al2O3 and SiO2 between the solid and the liquid phase of the aluminosilicate hydrogels prepared in a wide range of the batch concentrations [Na2O]bN, [Al2O3]bN, [SiO2]bN, and [H2O]bN as well as their molar ratios XbN = [Na2O]bN/[Al2O3]bN , YbN = [SiO2]bN/[Al2O3]bN and ZbN = [H2O]bN/[Al2O3]bN.

alkalinity; aluminosilicate hydrogels; chemical composition; distibution of Na;Si and Al; liquid phase; solid phase

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