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Article Dans Une Revue Journal of Colloid and Interface Science Année : 2010

Identification of solvated species present in concentrated and dilute sodium silicate solutions by combined 29Si NMR and SAXS studies

Résumé

Both concentrated and diluted sodium silicate solutions have been investigated by combining 29Si NMR spectroscopy and SAXS experiments. The chemical nature of the entities responsible for the high siliceous species solubility observed in such alkaline concentrated sodium silicate solutions and their evolution according to dilution have been identified. For the most concentrated solution ([Si] = 7 mol/l; pH = 11.56; Si/Na atomic ratio = 1.71), the results evidence the preponderant presence of neutral Si7O18H4Na4 complexes, which behave like colloids of about 0.6-0.8 nm able to form very small aggregates with an average size lower than 3 nm. Addition of distilled water to this initial concentrated solution leads, on one hand, to a doubling of the colloid size, i.e. 1.2-1.5 nm, and, on the other hand, to a progressive decrease of the aggregate size until their total disappearance. Such a behavior could be explained by considering, first, the dissociation of the neutral Si7O18H4Na4 complexes present in the concentrated solution into Na+ ions and charged (Si7O18H4Na4−n)n− complexes (with 1 ⩽ n ⩽ 4) and, second, the condensation of these siliceous charged species in order to form larger (Si7yO18y−zH4y−2zNa(4−n)y)ny− colloids. The mean size of these colloids suggests that the condensation occurs between 2 and 8 (Si7O18H4Na4−n)n− groups.

Dates et versions

hal-00608507 , version 1 (13-07-2011)

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Monique Tohoué Tognonvi, Dominique Massiot, André Lecomte, S. Rossignol, Jean-Pierre Bonnet. Identification of solvated species present in concentrated and dilute sodium silicate solutions by combined 29Si NMR and SAXS studies. Journal of Colloid and Interface Science, 2010, 352 (2), pp.309-315. ⟨10.1016/j.jcis.2010.09.018⟩. ⟨hal-00608507⟩
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