Supercritical Fluid Extraction of Acidic, Polar Solutes from Aqueous Matrices:  Partitioning Data for Pentachlorophenol between Carbon Dioxide and Water

Abstract

Supercritical fluid technologies as alternative methodologies to conventional procedures are being explored for the direct extraction of acidic and polar contaminants from aqueous matrices. In support of the knowledge required to implement these novel methods, the partitioning of pentachlorophenol between water and liquid and supercritical CO2 has been characterized by determining distribution coefficients at (18.8, 41.7, and 59.8) °C from a saturated water solution (11.6 × 10-6 g/g solvent). The partitioning of pentachlorophenol from dilute solution (1.27 × 10-6 g/g solvent) was measured at (42.2 and 59.9) °C. Distribution coefficients were lower at this reduced concentration. Measurements were made at pressures up to about 280 bar. Comparison of the partitioning data to the solubility ratio of the solute in both phases contributes to the interpretation of relevant interactions in this complex system.

Partition Coefficients of Organics between Water and Carbon Dioxide Revisited: Correlation with Solute Molecular Descriptors and Solvent Cohesive Properties

“…Finally, eq was employed to correlate the K -factor data in the most extensive data set mentioned above (455 data points for 44 solutes), − including the K -factor values for lower alkanoic acids calculated from selected phase equilibrium data reported by Panagiotopoulos et al Calculated and experimental values are compared in Figure , and the statistical parameters of the correlation are given in Table .…”

“…Partitioning of an organic solute i between both phases has often been characterized in terms of K -factor defined by where y i is the equilibrium molar fraction of the solute in the CO 2 -rich phase and x i is the equilibrium molar fraction of the solute in the water-rich phase. The experimental K -factor data were taken from the original sources. − However, some of the solutes, notably pentachlorophenol, 2,3,4,5-tetrachlorophenol, 3-methyl-4-chlorophenol, and 2-methyl-4,6-dinitrophenol and propiophenone were omitted because of the lack of vapor pressure data at the required temperatures (see below). Therefore, the most extensive set of experimental K -factor data comprised 455 data points for 44 solutes of diverse structures and falling within the temperature range of 297–363 K and the pressure range of 2.5–31.5 MPa.…”

“…The experimental K-factor data were taken from the original sources. 13−26 However, some of the solutes, notably pentachlorophenol, 19 2,3,4,5-tetrachlorophenol, 21 3-methyl-4-chlorophenol, 22 and 2-methyl-4,6-dinitrophenol 22 and propiophenone 23 were omitted because of the lack of vapor pressure data at the required temperatures (see below). Therefore, the most extensive set of experimental Kfactor data comprised 455 data points for 44 solutes of diverse structures and falling within the temperature range of 297−363 K and the pressure range of 2.5−31.5 MPa.…”

“…Phase behavior of systems containing water, carbon dioxide and organics has been relevant to several environment- and energy-related fields including carbon capture and storage, − CO 2 sequestration and CO 2 -assisted enhanced oil recovery. , A minor but distinct area of application has also been supercritical fluid extraction of aqueous media as a sample treatment technique of analytical chemistry. − Consequently, partitioning of organics between supercritical CO 2 and water or brine is an important topic, and there have been a number of experimental studies aimed either at the determination of solute partition coefficients ( K -factors) in CO 2 –water systems at low concentrations of the organic solute − or at the study of phase equilibria at finite concentrations of all components. − In line with the experimental studies, several approaches to modeling the CO 2 –water–organic systems have been applied although the overall number of such models does not match the large attention received by the CO 2 –water binary system. Equation of state (EoS) models of the CO 2 –water–organic(s) systems such as those employing the Peng–Robinson EoS ,,, or the perturbed-chain statistical associating fluid theory provide good description of the phase equilibria, however, at the expense of introducing unlike interaction (binary) parameters.…”

Determination of Organic Partitioning Coefficients in Water-Supercritical CO2 Systems by Simultaneous in Situ UV and Near-Infrared Spectroscopies

“…Curren et al reported higher partitioning coefficients for pentachlorophenol when the aqueous phase was initially saturated. 29 The authors speculated that increased solute−solute interactions (e.g., dimer formation) enhanced the compound's solubility in the CO 2 phase. However, such an effect would likely be less significant for nonpolar molecules such as benzene.…”