Effect of Ionic Surfactants on the Settling Behavior of Silt

Abstract

Ionic surfactants are easily adsorbed by silt and clay particles, thus affecting the flocculation characteristics and settling behavior. The settling velocity, Zeta potential and surface tension of silt flocs were measured in this paper. The results indicated that the cationic surfactant could dramatically accelerate the settling of slit particles, while the anionic surfactant slightly retard silt sedimentation to some extent. In still water, the representative settling velocity increases exponentially with the increase of Cetyltrimethylammonium Bromide concentration, while decreases linearly as Linear alkylbenzene sulfonate concentration increases. In flowing water, with the increase of flow velocity, the effect of ionic surfactants on silt settlement is weakened because of the enhanced dispersion of silt particles and the breaking of flocs. Finally, the intrinsic influence mechanism was discussed based on the variations of silt particle properties. This systematic study can be used for further development of flocculation models.

Keywords: Anionic surfactant, Cationic surfactant, Flocculation, Settling velocity, zeta potential, Surface Tension