Application of pitzer ion interaction model in the determination of activity coefficient to natural brines with presence of boron

Abstract

The ionic interaction model developed by Pitzer is applied to determine activity coefficient of the evaporitic Andean deposits known as Salar de Loyoques, in northern Chile. This salar is located in the Altiplano zone of the region of Antofagasta-Chile, at 4430 meters above sea level. The main characteristic of the salar is that in its center it has a borax deposit with exploitable levels of ulexita, a double borate of sodium and calcium. The solubilities of the minerals and the activity coefficients were calculated based on thermodynamics fundamentals using the software PHRQPITZ. In this context, the objective of this work was to evaluate the activity coefficients and the mineralogical sequence of the salar brines. The results indicate that the waters of the Loyoques salar´s show considerable variations both in their composition and their concentration but are slightly alkaline, and belong to the type Na-Cl-SO4. All the waters that enter this closed basin, subjected to processes of concentration by evaporation which causes the precipitation of calcite and later the samples that are closer to balance will be the gypsum and magnesite.