Density, Viscosity, and Structure of Equilibrium Solvent Phases in Butyric Acid Extraction by Phosphonium Ionic Liquid

Abstract

Density, viscosity, and dynamic light scattering (DLS) measurements have been done for quaternary phases with phosphonium ionic liquid (Cyphos IL-104 + dodecane + BA + water) from the extraction of butyric acid (BA) by a binary solvent (IL + dodecane). Density data show volume contraction in the solvent. Addition of water, BA, or dodecane considerably decreases IL viscosity, while BA decreases viscosity less than water. When increasing BA concentration, viscosity of the solvent phase in equilibrium without dodecane goes through a maximum at BA mass fraction of about 0.2. In solvents with more than 30% in mass fraction of dodecane, almost no influence of BA on viscosity was observed. Viscosity of water saturated solvents with IL concentration below 50% in mass fraction is markedly higher than in solvents containing also BA. This is due to the formation of dodecane-rich micelles in water saturated solvents which increase IL concentration in the bulk of the solvent. No large aggregates with size above 100 nm...