Synergistic effect of polymer-surfactant mixtures on the stability of aqueous silica suspensions
The aim of the present work was to investigate the effect of cationic/nonionic surfactant mixtures on the dispersion and flocculation behavior of aqueous silica suspensions. In the study dodecylamine (DDA) was used as the cationic surfactant and polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymers were employed as the nonionic surfactant. The dispersion and flocculation behavior of aqueous silica suspensions were studied mainly by turbidity measurements at low solids loading (0.05 vol.%) to observe the stability of the system for a given time period. Rheological measurements were performed at higher solids loadings to determine the viscosity as a function of shear rate. Adsorption behavior of single and mixed surfactants onto silica surface was studied using a total organic carbon analyzer. Results of the study showed that dispersion and flocculation behavior of aqueous silica suspensions depends on the type and concentration of surfactant, cationic/nonionic surfactant ratio and surfactant addition sequence to the system.