Thermodynamic Properties of 1:1 Salt Aqueous Solutions with the Electrolattice Equation of State

Abstract

Re´sume´-Proprie´te´s thermophysiques des solutions aqueuses de sels 1:1 avec l'e´quation d'e´tat de re´seau pour e´lectrolytes -L'e´quation d'e´tat, dite e´lectrolattice, est un mode`le qui e´tend l'e´quation d'e´tat de Mattedi-Tavares-Castier a`des syste`mes avec e´lectrolytes. Ce mode`le prend en compte l'effet de trois termes. Le premier terme est base´sur les trous dans le re´seau en conside´rant les effets de la composition locale, e´tude effectue´e dans le cadre de la the´orie ge´ne´ralise´e de Van der Waals : l'e´quation d'e´tat de Mattedi-Tavares-Castier a e´te´choisie pour ce premier terme. Les deuxie`me et troisie`me termes sont les contributions de Born et du MSA. Ils tiennent compte du chargement et du de´chargement des ions, et des interactions ioniques al ongue distance, respectivement. Le mode`le n'ayant besoin que de deux parame`tres d'interaction e´nerge´tique, il mode´lise de manie`re satisfaisante la pression de vapeur et le coefficient d'activiteí onique moyenne pour des solutions aqueuses simples contenant du LiCl, LiBr, LiI, NaCl, NaBr, NaI, KCl, KBr, KI, CsCl, CsBr, CsI, ou du RbCl. Deux me´thodes pour obtenir les parame`tres du mode`le sont pre´sente´es et mises en contraste : une me´thode spe´cifique pour le sel en question et une autre base´e sur les ions. Par conse´quent, l'objectif de ce travail est de calculer les proprie´te´s thermophysiques qui sont largement utilise´es pour la conception, l'exploitation et l'optimisation de nombreux proce´de´s industriels, parmi eux le dessalement de l'eau.Abstract -Thermodynamic Properties of 1:1 Salt Aqueous Solutions with the Electrolattice Equation of State -The electrolattice Equation of State (EOS) is a model that extends the MattediTavares-Castier EOS (MTC EOS) to systems with electrolytes. This model considers the effect of three terms. The first one is based on a lattice-hole model that considers local composition effects derived in the context of the generalized Van der Waals theory: the MTC EOS was chosen for this term. The second and the third terms are the Born and the MSA contributions, which take into account ion charging and discharging and long-range ionic interactions, respectively. Depending only on two energy interaction parameters, the model represents satisfactorily the vapor pressure and the mean ionic activity coefficient data of single aqueous solutions containing LiCl, LiBr, LiI, NaCl, NaBr, NaI, KCl, KBr, KI, CsCl, CsBr, CsI, or RbCl. Two methods are presented and contrasted: the salt-specific and the ion-specific approaches. Therefore, the aim of this work is to calculate thermodynamic properties that are extensively used to design, operate and optimize many industrial processes, including water desalination.

An electrolyte CPA equation of state for mixed solvent electrolytes

“…In literature many approaches for defining the effective hydration radius have been suggested. Some researchers adopt the diameter (“distance of closest approach”) from the Debye–Hückel term, while others use adjusted hydrated diameters, where the ion diameters are typically slightly increased (compared to the hard‐sphere diameter ), presumably due to the effect of hydration. Only Myers et al and Herzog et al performed comparisons of calculated values to experimental values of the Gibbs energy of hydration at 25°C and both showed large deviations.…”

The Debye-Hückel theory and its importance in modeling electrolyte solutions

“…The remaining reduction of static permittivity due to formation of hydration shells around ions can be modeled using ion-solvent association, as shown by Maribo-Mogensen et al 48 and recently also applied in the work by Shahriari and Dehghani 44 . However, most studies 23,[26][27][28][29]33,[78][79][80][81][82] that have included the effect of the reduction in the static permittivity on the activity coefficient from Debye-Hückel have used the unmodified data, thereby included an unphysically strong effect of electrolytes on the static permittivity which must be compensated by the remaining parameters.…”

Simultaneous Description of Activity Coefficients and Solubility with eCPA

“…As discussed by Maribo-Mogensen et al 17 , different approaches for estimating this parameter can be found in literature. Some have used the same diameter as used in the Debye-Hückel or MSA term 14,22,39 , but others have used an adjustable diameter, typically increased due to the effect of hydration compared to the hard-sphere diameter 16,18,[40][41][42][43][44][45][46] . Maribo-Mogensen et al 17 estimated the Born radius to match the hydration enthalpy at 298.15 K calculated with eCPA, as the Born term has by far the most significant contribution to this property.…”