Silica particle growth in metastable supersaturation solution

In a metastable solution the particle growth rate of silicon dioxide increased with an increase in the initial supersaturation of the metastable solution and agitation speed in the ranges of 2.5 × 10−4 to 2.0 × 10−3 M and 300–1500 rpm, respectively. Based on a power law expression, the particle growth rate order was estimated as 2.0 independent of the initial supersaturation and agitation speed. Meanwhile, the particle growth rate coefficient was enhanced from 2.0 × 10−3 to 1.4 × 10−2 with increase in the agitation speed from 300 to 1500 rpm. From the experimental data, it would appear that the enhanced particle growth rate resulted from the promotion of molecular transport due to the agitation and driving force of the supersaturation in the particle growth process. A slight addition of sodium chloride into the metastable solution caused a marked reduction of the particle growth rate due to the inhibition of growth process by sodium chloride adsorbed on the particle. This effect of sodium chloride on the particle growth appeared in a significant drop of the particle growth rate coefficient from 4.5 × 10−3 to 8.0×10−4 with increase in the sodium chloride concentration from zero to 5.0×10−3 M, but not in the particle growth rate order. The influence of sodium chloride on the particle growth process of silicon dioxide predicted with a Langmuir isotherm matched with the experimental data.