A View on Thermodynamics of Concentrated Electrolytes

Electrolytes, on dissolution, reduce the activity of water. This fact is utilized numerous applications in the areas of desalination of water, oil production, precipitation and corrosion in pipelines, the removal of CO2 from flue gases of power plants, and in biotechnology. The classical theory for prediction of the water activity is the Debye-Hückel. However, Debye-Hückel theory is not accurate in concentrated solutions. At higher concentration, the electrostatic interaction between the central ion and the surrounding counterions is significantly stronger than the region outside where the bulk dielectric constant of water prevails. As the electrolyte concentration increases, the probability of finding the counterion in the low dielectric constant region in the vicinity of the central ion progressively increases. This causes deviation of the electrostatic interaction from the Debye-Hückel theory. So, an improved theory should not only correctly account for the nonelectrostatic interaction, but also appropriately modify the Debye-Hückel theory for electrostatic interaction.