“Analysis of data consistency for electrolyte systems”
Abstract
In the recent days, the need to find and improve the thermodynamic models, making them more precise and predictable for complex systems, has increased. Electrolyte systems are characterized by their complexity.
This complexity is caused by the strong interactions between ions, the hydration forces that take place during salt dissociation, and due to the physical forces at high concentration of solute. These forces make difficult the precise calculations of phase equilibrium in electrolyte mixtures.
Consequently, the existing thermodynamic electrolyte models show some limitations and are far from being completely optimized for industrial simulations. Thermodynamics based on electrolyte mixtures and mixed solvents requires further development and research.
To deal with that problem, the present work presents a strategy to analyze the internal and external consistency of experimental data for electrolyte mixtures. A simple methodology to describe and relate the most important properties in a specific system has been developed (internal consistency).
For that purpose, the selection and analysis of a model is necessary. The Bromley model, characterized by its simplicity (only depends on one adjustable parameter), was selected after being compared to other simplified models. As far as that, the adjustable parameter B of Bromley has been analyzed and compared for different electrolyte systems in order to determine a relation between the adjusted Bromley parameter and the physical properties of the components.
In order to improve and analyze the consistency, the Bromley parameter was optimized an studied at different conditions (external consistency). The accuracy, the validity and the applicability of the model was obtained by the comparison with experimental data. The electrolyte systems represent a mixture between salts and solvent at different conditions (temperature, pressure or concentration of electrolytes).
The systems studied were composed by the most common monovalent salts, pure water and an a primary alcohol (methanol, ethanol, 1-propanol, 1-butanol). The available data of the described systems have been summarized and analyzed. The data properties studied in the present work for electrolyte mixture studied: The mean ionic activity coefficients (ɤ), the vapor-liquid equilibrium (VLE), the osmotic coefficient (ϕ), and the enthalpies of solution.