Henry's Constant in Mixed Solvents from Binary Data

Abstract

The Kirkwood−Buff formalism was used to derive an expression for the composition dependence of the Henry's constant in a binary solvent. A binary mixed solvent can be considered as composed of two solvents, or one solvent and a solute, such as a salt, polymer, or protein. The following simple expression for the Henry's constant in a binary solvent (H 2 t ) was obtained when the binary solvent was assumed ideal: ln H 2 t = [ln H 2,1(ln V − ln ) + ln H 2,3(ln − ln V)]/ (ln − ln ). In this expression, H 2,1 and H 2,3 are the Henry's constants for the pure single solvents 1 and 3, respectively; V is the molar volume of the ideal binary solvent 1−3; and V 1 0 and V 3 0 are the molar volumes of the pure individual solvents 1 and 3. The comparison with experimental data for aqueous binary solvents demonstrated that the derived expression provides the best predictions among the known equations. Even though the aqueous solvents are nonideal, their degree of nonideality is much smaller than those of the solute gas in each of the constituents. For this reason, the ideality assumption for the binary solvent constitutes a most reasonable approximation even for nonideal mixtures.

Process Analysis of Ionic Liquid-Based Blends as H2S Absorbents: Search for Thermodynamic/Kinetic Synergies

“…Figure shows the Henry’s law constant mixing deviations of H 2 S in equimolar IL-based blends (Δ K Henry H2S ) for more than 400 equimolar [Emim]­[(MeO)­PO 2 H]–IL 2 mixtures and [Emim]­[(MeO)­PO 2 H]–TGM mixtures plotted against the activity coefficient of [Emim]­[(MeO)­PO 2 H] (Figure A) in the IL-based blends. In good agreement with the conclusions of the Shulgin model, a relationship between Δ K Henry H2S in IL-based blends and the reference activity coefficient of the absorbents in the equimolar IL-based blends was found (γ [Emim][(MeO)PO2H] ). Thus, the solvent mixing effect on H 2 S solubility could be openly classified in a thermodynamic context.…”

Thermodynamics of fluid‐phase equilibria for standard chemical engineering operations

“…A better approximation is often obtained by assuming additivity of binary interactions. In that case, for a ternary mixture, we need not only H j for gas j in both pure solvents but, in addition, some information on interactions in the binary (gasfree) solvent mixture (Campanella et al, 1987;Shulgin and Ruckenstein, 2002).…”

Local Fluctuations in Solution: Theory and Applications

“…14,42 In particular, KB theory has been applied to study low solute solubility in water by deriving KB based expressions for Henry’s constant. 47 These studies typically used closed ensembles, sparingly soluble solutes, with solubilities and cosolvent concentrations expressed using mole fractions. Hall, 42 and more recently Mazo, 16 recognized that the most appropriate ensemble for these studies was one where T, P, and the chemical potential of the solute are held constant.…”