On the symmetrical and unsymmetrical reference state for ionic liquids modeling: Electrolytes versus neutral compounds

Abstract

The symmetrical and unsymmetrical conventions for the reference state of the activity coefficients was applied to the Pitzer-Debye-Hückel (PDH) equation to describe long-distance interactions coupled with the UNIversal QUAsi-Chemical (UNIQUAC) model to describe short-distance interactions in binary temperature-composition (T, x) data. Based on the results of a previous work related to the closest approach parameter (ρ), in the PDH equation, a novel methodology was refined in order to obtain a more accurate description of the behavior of ionic liquids (ILs) in water. The aim of this work is to step further in a modern methodology that considers ILs as charged compounds, i.e., species that dissociate, while accounting for this dissociation extent. This study intends to set the groundwork for powerful and valuable tools for the scientific community in the field of chemistry, geology, material science, medicine, biochemistry, as well as in many engineering areas, such as chemical, biochemical, electrical and petroleum engineering.