POLYACRYLAMIDE NA-KAOLINITE INTERACTIONS - EFFECT OF ELECTROLYTE CONCENTRATION ON POLYMER ADSORPTION

The variation in polyacrylamide adsorption on Na-kaolinite as a function of electrolyte concentration of the clay suspension, was determined under three pH conditions, where the clays display varying charge characteristics. Interpretation of the results is based on two arguments: non-charged polyacrylamide adsorption is restricted to the edge faces of the colloidal platelets and hydrogen bonding between the amide groups of the polymer and the 'isolated' hydroxyl sites of these faces is the mode of surface attachment. At constant pH, when Na-kaolinite bears charged surface groups, the polymer adsorption, which is related to the density of the anchoring sites, parallels the state of ionization of the edge surface.