Aggregation and growth of model silica particles

Abstract

In this thesis study, the stability and the flocculation behavior of silica colloidal particles in aqueous system in the presence of a polymer and a surfactant were investigated. The size of particles and floes were measured using Dynamic Light Scattering (DLS). The major experimental parameters used for studying the stability of silica colloids were the amount of salt, shear rate, molecular weight of polymer and the chain length of surfactant. The experiment shows that CTAB is effective in controlling the floe size. For silica particles of 7,000 ppm in water, the floe size increases with increasing concentration of CTAB from 0 to 100 ppm. The largest floe size was found at 100 ppm CTAB. In cases of the CTAB concentrations of more than 100 ppm, the floe size was found to decrease with increasing CTAB concentration. The rate of shear also played an important role in the size of silica floes. High shear rate could break the particle bond and stabilize the system. The viscosity effect in the presence of polymer was also investigated. Low molecular weight polyacrylamide was not effective for stabilizing the silica particles. On the other hand the high molecular weight one was effective since the effect of viscosity was more significant than the effect of polyacrylamide in stabilizing the silica particles.