Colloidal charge reversal: Dependence on the ionic size and the electrolyte concentration.

Extensive Monte Carlo simulations and scaling arguments are used to study the colloidal charge reversal. The critical colloidal surface charge density sigma(c) at which the reversal first appears is found to depend strongly on the ionic size. We find that sigma(c) has an inflection point as a function of the electrolyte concentration. The width of the plateau region in the vicinity of the inflection point depends on the temperature and the ionic radius a. In agreement with the theoretical predictions it is found that the critical colloidal charge above which the electrophoretic mobility becomes reversed diverges as Z(c) approximately 1/a(2) in the limit a-->0.