Modelagem e predição de propriedades termodinâmicas de misturas aquosas contendo eletrólitos fracos e fortes empregando a equação de estado q-electrolattice

Abstract

In order to better represent thermodynamic properties of aqueous solutions containing strong and weak electrolytes, the present study applies two different methodologies to obtain parameters of the Q-electrolattice equation of state. The first one considers an approach previously published in the literature, which was specifically developed for the calculation of solutions containing strong electrolytes. In this first methodology, two strategies for obtaining the parameters are tested: one considering the adjustment of the ion-solvent interaction, the ionic diameter, and the ion-ion interaction; the second considers parameters obtained in a previous work and adjusts only the ion-ion interaction. The second methodology, which was fully developed in this work, takes into account the formation of ionic pairs in solution. In it, three estimation strategies were tested, in which the ion pair-solvent interaction parameter, ion pair diameter, and association constant are obtained. The difference between these strategies lies in the fact that the ion pair diameter is considered as the average of ion diameters estimated in another work, the sum of these values or is freely adjusted. Both methodologies were applied to the Q-electrolattice model in order to describe properties such as the mean ionic activity coefficient and the densities of aqueous solutions of lithium, sodium and potassium chlorides, bromides, and iodides, acidic solutions of HCl, HBr, and HI, basic solutions of LiOH, NaOH, and KOH, as well as solutions of weak electrolytes such as acetic acid and lithium, sodium and potassium acetates. From the application of the methodologies, the Q-electrolattice model becomes capable of calculating these properties at higher concentration values, a condition in which the ionic associations are found. Finally, the present work emphasizes that the parameter estimation methodology considering the formation of ionic pairs makes the model more accurate for both strong and weak electrolytes.