Electrokinetic Interactions between Two Spheres: The Role of Surface Charge Transport in Coagulation

✍ Scribed by Joseph W. Krozel

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 806 KB
• Volume: 163
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1994.1123

✦ Synopsis

A model which incorporates an electrokinetic characterspecifically, nonequilibrium charge transport within a particle surface layer-into the classical DLVO framework for colloid stability is developed. Particular attention is devoted to the physical scaling arguments that justify the inclusion of unsteady charge transport. Additional scaling arguments find the Smoluchowski framework of Brownian motion valid, whereas transverse particle motion contributes insignificantly. Next, a perturbation scheme which poses the electrokinetic correction to particle motion as a higher order correction to the classical electrostatic contribution is devised. This perturbative approach resembles that of S. S. Dukhin and J. Lyklema (Langmuir 3, 94 (1987)) in their article "Dynamics of Colloid Particle Interactions." The present effort is unique in adhering to an equilibrium charge structural model at the particle surface even in the presence of nonequilibrium charge transport. Finally, the effect of varying the model parameters on the magnitude of the (colloid) stability ratio (W) is demonstrated. It is concluded that the electrokinetic effect is generally quite small under representative conditions covered by the present model-the main restriction is the limitation to particle surface potentials less than (25.7 \mathrm{mV}). Nevertheless, a discernible correction to the stability ratio can be expected for slow-diffusing electrolyte species, e.g., polyelectrolytes, particularly when their residence upon the particle surface is substantial. 1994 Academic Press, Inc.