Simulations of the adsorption of ionic species at polarisable liquid∣liquid interfaces

The adsorption of ions at the interface between two immiscible electrolyte solutions (ITIES) is primarily controlled by the potential distribution across the interface, which in turn is influenced by the adsorption process. In the present paper, we simulate the effect of the adsorption of charged species on the charge distribution at the ITIES based on the classical description of the interface employing the Gouy-Chapman model. The inner layer is considered as a charged plane, where the ionic adsorption takes place. The potential at this plane is determined by the electro-neutrality condition. Various adsorption isotherms are considered, including potential dependent isotherms based on the Langmuir and Frumkin adsorption models. The potential distribution and the charge density profile are derived by solving the Poisson-Boltzman equation numerically. We show that the charge distribution in the interfacial region is significantly affected by the adsorption of ionic species. Under certain conditions, the adsorption results in a non-monotonic potential distribution with a potential trap at the interface.