Solubility of Sodium Halides in Aqueous Mixtures with ε-Increasing Cosolvents: Formamide, N-Methylformamide, and N-Methylacetamide at 298.15 K

Abstract

The solubility data for sodium halides (NaF, NaCl, NaBr, and NaI) have been determined at 298.15 K in the ε-increasing mixtures of water–formamide, water–N-methylformamide, and water–N-methylacetamide. In all cases, the solubility of the electrolytes was decreased significantly in the presence of a cosolvent. The solubility of an electrolyte in a given solvent depends on both the nature of the solvent (mainly the polarity, dielectric constant, solvation, or preferential solvation if the solvent is a mixture of solvents, etc.) and the properties of the electrolyte (principally the size, the charge, and the possible association of its ions). If the molality of saturation is not sufficiently small, the ion–ion and ion–solvent interactions must be considered. Although it was not the objective of this work, the solubility values were qualitatively correlated with several properties of the solvent and solute. Finally, a simple justification, which was both qualitative and quantitative, was carried out.

Solute displacement in the aqueous phase of water–NaCl–organic ternary mixtures relevant to solvent-driven water treatment

“…4 Ternary phase diagrams examining the aqueous-rich phase of water-NaCl-MOS for: (A) alcohols; (B) acetone; (C) amides; and (D) other polar solvents. Solid symbols denote data points measured in this work, while hollow symbols represent literature data from Marcilla et al 20,21 for ethanol, butanol and acetone and from Hernandez et al 22 for N-methylacetamide presented here for comparison and validation. Square and circular markers denote protic and aprotic solvent, respectively.…”

“…3 and from the literature. [20][21][22][60][61][62][63][64][65][66] 3.2.2 Scenario 3solute displacement mechanism. Rather than assuming zero solute interactions between MOS and water, and between MOS and NaCl, it may be more useful to conceptualize the solubility of an ionizable salt from the thermodynamics of solvation, via Hess's Law.…”

“…It is however possible to consider other salts. Based on the water- NaF-NMA system, 22 salts that saturate at low salt mole fractions (<0.03) appear to deviate from one-to-one displacement phenomenon. Perhaps sparingly soluble salts are less sensitive to the water concentration which is in large excess at their saturation in contrast to highly soluble salts where the water concentration is on the same order of magnitude as the salt at saturation (especially when hydration is considered).…”

“…To understand the relative performance of DME, we characterized the aqueous phase of the liquid-liquid equilibria of twelve water-NaCl-MOS ternary mixtures, and compared the results to existing data available in the literature. [20][21][22] The measurements presented provide key insights into the mechanism of MOSdriven FP, which have implications for fundamental electrolyte solvation phenomena.…”

“…Surprisingly, very few experimentally determined phase diagrams exist for watersalt-MOS systems. [20][21][22][60][61][62][63][64][65][66] To close the knowledge gaps associated with ternary phase behavior of water-NaCl-MOS systems for FP, we have experimentally obtained the aqueous phase boundaries for twelve different MOSs, expanding on four relevant datasets that we found in the literature. [20][21][22] Based on these data, we have developed a conceptual model for the mechanism of MOS-driven FP.…”