Influence of reactivity of the colloidal silica on the properties of conjugate phasesстатья
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Дата последнего поиска статьи во внешних источниках: 21 сентября 2017 г.
Аннотация:The properties of hydrosols (brand Ludox) are studied by dynamic light scattering (photon correlation spectroscopy, PCS) and colorimetric analysis (formation of a colored beta-silicomolybdate complex, KMK). Experimental sol samples for silicate modulus M = 50.0 and De = 3.0 M (M = [SiO2]/[Me2O], mol/mol) are obtained by introducing an alkali metal hydroxide (Me). According to the PCS data, the hydrodynamic radius of the sol particles (= 41.0 g/L) is r = 8.0 nm and increases with the dilution of the sol. These particles' radii r (a) (at -> 0) for the initial sol are r (a) = 13.8 nm and r (a) = 16.8 nm in sols with alkali metal hydroxides (M = 50). The conjugated phase properties (silica particles and aqueous solution) were considered in the light of polycondensation and depolymerization kinetic reactions involving reactive silicate anions (HO)(3)SiO- and Si(OH)(4)) on the surface of the particles and in the composition of soluble fractions. The result is the formation of surface layers of a gel-like structure. With the introduction of alkali metal hydroxides, the initial dissolution rate increases in the range from LiOH to KOH. The existence of peaks in the kinetic dependences of the active silica fractions in highly alkaline environments (M = 50 and M = 3.0) characterizes the secondary polycondensation of silicic acid in the aqueous phase, resulting in the formation of the oligo- and polymeric molecules of a linear structure.