Possibilities of Colloidal Silica Separation from Water Suspension in the Polyethylene Glycol (PEG) Presence at Different Temperatures

The influence of polyethylene glycol (PEG) adsorption on the silica (SiO2) suspension stability was examined in the range 1535 degrees C. For this purpose the following methods were applied: turbidimetry, spectrophotometry, and microelectrophoresis. They allow determination of silica suspension stability, its absorbance, and zeta potential of the solid particles in the absence and presence of the polymer. The obtained results indicate that both polymer adsorption and temperature influence the stabilization-flocculation properties of the systems under examination. The silica suspensions without the polymer are relatively stable in the whole range of the investigated temperatures (electroststic stabilization). The adsorption of polyethylene glycol with lower molecular weight (PEG 2000) practically does not change the stability properties of the suspension (steric stabilization), whereas the adsorption of PEG with the higher molecular weight (20000) causes its deterioration (bridging flocculation). The higher the temperature is the greater the effect of destabilization is obtained. Such behavior of the investigated system is the result of changes in the structure of the polymer adsorption layer with the increasing temperature.