Dynamic stability ratio of a colloidal dispersion

The stability ratio of a dispersed system containing colloidal particles having amphoteric surfaces is estimated theoretically. We consider the case where the degree of dissociation of the functional groups on particle surface as a response to the variation in the conditions of the surrounding liquid phase is a function of time. The dynamic nature of the distributions of ions in the electrical double layer near a particle is also taken into account. The result of numerical simulation reveals that the dynamic nature of the system under consideration has the effect of increasing its stability. Due to the fact that the diffusivity of protons in the aqueous solution is much larger than that of other ion species, the level of increase in the stability ratio is less than similar to 40%. However, if the rates of surface reactions are slow, the dynamic stability ratio can exceeds ten times the corresponding equilibrium value. Also, the smaller the particle and/or the thicker the double layer, the more significant the dynamic behavior of the system under consideration. (C) 1999 Elsevier Science. All rights reserved.