Interaction forces between silica surfaces in aqueous solutions of cationic polymeric flocculants: Effect of polymer chargen

Abstract

Three cationic polymers with molecular weights and charge density of 3.0 × 105 g/mol and 10% (D 6010), 1.1 × 105 g/mol and 40% (D6040), and 1.2 × 105 g/mol and 100% (D6099) were investigated in aqueous NaCl solutions in the presence of silica. The atomic force microscope (AFM) colloidal probe technique was used to determine silica interparticle interaction forces, which were compared to macroscopic information on the strength of interactions such as compressive yield stress measurements. It was found that in 30 mM NaCl solution the 10% charged polymer produced steric repulsion upon approach and long-range adhesion with multiple pull off events upon retraction at the optimum flocculation conc..