Abstract
The mechanism of the flocculation and deflocculation of Veegum (Montmorillonite) in an aqueous medium by polyoxyethylene hydrogenated castor oil which has a various length of polyoxyethylene chains, has been examined by adsorption isotherm, viscosity, zeta potential and contact angle measurements. Adsorption isotherms for these surfactants on Veegum showed flectional points (S-shaped) at a certain concentration of the surfactants added. The maximum flocculation occurred around the flectional points accompanying high viscosity in the suspension, and the measurement of contact angles showed that the Veegum surface at these points was most hydrophobic. These results suggest that the maximum flocculation occurs when all the Veegum surfaces are covered by surfactants orientating the hydrocarbon chains toward the solution, which renders the surface more hydrophobic. The deflocculation caused by the further addition of the surfactants is interpreted as being due to the bimolecular layer adsorption of the surfactants by van der Waals forces or by hydrophobic bonding between the Veegum particles adsorbed surfactants monomolecularly and the surfactants added.
