Polyelectrolyte Adsorption Kinetics, 1995 Papermakers Conference Proceedings

Matthew H. Lang’ Robert A. Stratton* The Institute of Paper Science and Technology The main objectives of this work were to measure the rate of polyelectrolyte adsorption in a model colloidal system, and to study the impact of several variables on the rate of adsorption. The system consisted of aqueous polyallylamine and polystyrene latex adsorbent. A previously developed theoretical model was tested by determining the effects of polyelectrolyte concentration, and dispersed adsorbent concentration on the rate of polyelectrolyte adsorption. The influence of polyelectrolyte molecular weight, polyelectrolyte charge density, and adsorbent surface charge density were investigated under perikinetic conditions. The effect of polyelectrolyte molecular weight was studied under orthokinetic (laminar flow) and turbulent conditions. The model was verified by showing that the rate of polyelectrolyte adsorption was first-order with respect to both bulk polyelectrolyte concentration and dispersed adsorbent concentration. The rate of polyelectrolyte adsorption decreased as the molecular weight of the polyelectrolyte increased under all flow regimes. The adsorption rate constants for the high charge density (0.80) polyelectrolytes were found to be greater than those of the low charge density (0.15) polyelectrolytes of the same molecular weight. The rate of adsorption increased as the latex charge density increased due to the increase in the adsorption capacity of the latex. Examples of adsorption rates under papermaking conditions are given in terms of time to adsorb 90% of a cationic polymeric additive.