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 $Z_c\sim 1\mathrm{/}{a}^2$ in the limit $a\to 0$.