title: Adsorption and stabilizing effects of highly-charged latex nanoparticles in dispersions of weakly-charged silica colloids.
abstract: An experimental study was undertaken to determine the effectiveness of using highly-charged nanoparticles as stabilizers for colloidal dispersions. The specific systems used here involved cationic (amidine) and anionic (sulfate) polystyrene latex nanoparticles with an approximate diameter of 20 nm and silica microparticles of diameter 1.0 μm, and experiments were conducted at the isoelectric point of the silica. It was found that while both types of nanoparticles adsorbed to the silica microparticles and increased the zeta potential to values where stability was expected, long term stability was not achieved, even at bulk nanoparticle concentrations as high as 0.5 vol.%. It is theorized that the incomplete coverage of the microparticles by the nanoparticles (i.e., surface coverage never exceeded 50%) allowed either direct contact between bare patches of the underlying microparticles or, alternatively, for nanoparticles adsorbed on one microparticle to bridge to bare spots on a neighboring microparticle.
authors.affiliation: Virginia Tech, Department of Chemical Engineering, Blacksburg, VA 24061, United States.
authors.forename: David
authors.initials: D
authors.lastname: Herman
authors.affiliation: University of Kentucky, Department of Chemical and Materials Engineering, Lexington, KY 40506, United States. Electronic address: john.walz@uky.edu.
authors.forename: John Y
authors.initials: JY
authors.lastname: Walz
keywords: Binary dispersions; Colloidal dispersions; Colloidal stability; Flocculation