ADSORPTION OF POLY(SODIUM(4)STYRENESULFONATE) ON COLLOIDAL IRON-OXIDEPARTICLES

The adsorption of poly(sodium(4)styrenesulfonate) (PSSNa) on colloidal iron oxide has been studied with several techniques. Measurements of the adsorption isotherm as well as the electrophoretic mobility and pa rticle size as a function of polymer concentration has been performed. Also, the electrophoretic mobility of both bare and PSSNa coated iron oxide has been studied as a function of pH. Results from the applied techniques individually demonstrate the adsorption of the polyelectrol yte to the iron oxide particle surface. In the absence of or at low po lymer concentrations (and pH 4) the suspension is stabilized by a high net positive charge from the exposed iron oxide surface. Intermediate concentrations yield unstable and precipitating suspensions, probably because of a low net surface charge due to the partial coating and ne utralization by adsorption of small amounts of the polyanionic polymer . At high polymer concentration the resulting suspension is again stab ilized, probably due to the build up of a multi-molecular layer of pol ymer and a high net negative surface charge.