Aplicación del Modelo de Interacción Iónica de Pitzer para determinar Coeficientes de Actividad en Salmueras Naturales con Presencia de Boro

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.

Boron Industry, Sources, and Evaporitic Andean Deposits: Geochemical Characteristics and Evolution Paths of the Superficial Brines

“…Contributions to different basins correspond, mainly, to meteoric and "thermal" waters that, when they reach the basins, of saline composition, evolve into chlorinated brines with lower carbonate and sulfate contents, although the latter can be enriched in situ [31,32]. The higher cations are sodium, calcium, potassium, magnesium, and lithium, with significant local amounts of arsenic and mercury, while the main anions are sulfates, chlorides, and carbonates, in addition to nitrates and borates [20,[33][34][35]. Additional factors that contribute in the formation of basins are erosion and leaching of different types of rocks; the transformation, in situ, of rocks by the chemical and physical action of the salts, through "saline tectonics"; biological activity; photochemical reactions; and mists ("camanchacas") and marine spray [36,37].…”

“…The basins of the andean salars have a structural control, some have been formed by entrapment flows of lava or inside ancient volcanic systems eroded, for example, boilers. The contributions to the basins are influenced by the volcanic activities that, in some salt flats, are evidenced in its interior by sources of thermal hot springs (Surire, Aguas Calientes I) [19,35]. The volcanic activity provides a high geothermal gradient that directly affects the quantity and quality of the leached transported ions to the basins [20,38].…”

“…The equilibrium constants used are those that appear in the database of the code used. Examples of similar studies are [35,[66][67][68].…”

Thermodynamic Model for the Design of a Process of Production of Copper Sulfate Pentahydrate from Copper Ores

“…In order to predict the salts that crystallize in the multicomponent system analyzed in the present work, the supersaturation index proposed by Krumgalz et al and Garcés has been used, where the degree of saturation of a brine with respect to a mineral of the formula M v M X v X · n H 2 O is defined by the following equation where the numerator of the equation is the product of the real ionic concentrations in a particular system and the denominator contains parameters, which are functions of temperature and pressure ( K sp , γ ± , a H 2 O n ). Activity coefficients are estimated by applying the Pitzer model (eqs and ).…”

“…Garcés used the ionic interaction model of Pitzer to determine activity coefficients of the evaporitic Andean deposits known as Salar de Loyoques in northern Chile. Through this model, the activity coefficients were evaluated, and it was determined that the first mineral precipitated was calcite, while gypsum and magnesite are close to equilibrium.…”