Reactive Monte Carlo Simulations for Charge Regulation of Colloidal Particles

TL;DR

This paper introduces a reactive Monte Carlo simulation method to study charge regulation in colloidal particles, accounting for acid-base equilibrium, ionic effects, and comparing results with experimental titrations.

Contribution

It presents a novel simulation approach that models charge regulation in colloids considering electrolyte effects and specific ion adsorption, aligning well with experimental data.

Findings

Good agreement between simulations and experimental titration curves for potassium chloride.

The model captures the impact of pH, salt concentration, and electrolyte type on colloidal charge.

Specific ionic adsorption effects are significant for lithium chloride cases.

Abstract

We use a reactive Monte Carlo simulation method and primitive model of electrolyte to study acid-base equilibrium that controls charge regulation in colloidal systems. The simulations are performed in a semi-grand canonical ensemble in which colloidal suspension is in contact with a reservoir of salt and strong acid. The interior of colloidal particles is modeled as a low dielectric medium, different from the surrounding water. The effective colloidal charge is calculated for different number of surface acidic groups, pH, salt concentrations, and types of electrolyte. In the case of potassium chloride the titration curves are compared with the the experimental measurements obtained using potentiometric titration. A good agreement is found between simulations and experiments. In the case of lithium chloride specific ionic adsorption is taken into account through partial dehydration of lithium ion.