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

TL;DR

This study uses Monte Carlo simulations and scaling arguments to explore how ionic size and electrolyte concentration influence colloidal charge reversal, revealing critical dependencies and divergence behaviors.

Contribution

It demonstrates the strong dependence of critical surface charge density on ionic size and electrolyte concentration, confirming theoretical predictions about divergence as ionic radius approaches zero.

Findings

Critical surface charge density depends on ionic size.

Charge reversal occurs at an inflection point in electrolyte concentration.

Critical colloidal charge diverges as ionic radius approaches zero.

Abstract

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