Calculation of the collective diffusion coefficient of electrostatically stabilised colloidal particles

The collective diffusion of concentrated suspensions of charged spheres is theoretically investigated. The analysis is based on a fundamental calculation of colloidal interactions between particles expressed in terms of osmotic pressure. The osmotic pressure accounts for multiparticle electrostatic interactions, dispersion forces, and configurational entropy effects. This osmotic pressure is used in the generalised Stokes-Einstein equation to derive the collective diffusion coefficient. This allows the prediction of the concentration dependence of the collective diffusion coefficient for various physicochemical conditions, such as particle size, surface charge or potential and electrolyte concentration. Results are compared with existing experimental data on the collective diffusion coefficient of bovine serum albumin, and to other dilute theories. Very good quantitative agreement is found. (C) 1998 Elsevier Science B.V.