Supercritical CO₂ extraction of organic contaminants from aqueous streams

Abstract

Abstract Supercritical fluid extraction (SCFE) for the removal of organic toxins from water has been studied using a continuous‐flow view cell system. Distribution coefficients (ratio of mole fraction of contaminant in supercritical CO 2 to mole fraction in the aqueous phase at equilibrium) have been determined for a homologous series of contaminants as individual components in pure water: benzene, phenol, p‐chlorophenol, and m‐cresol. Data were obtained at two temperatures (313 and 323 K) and over a pressure range of 9.65 to 17.23 MPa for each contaminant. The distribution coefficients of the contaminants follow a pattern that can be explained in terms of molecular interactions both with water in the aqueous phase (as quantified by the pure contaminant solubility in water) and with CO 2 in the SCF phase (as quantified by the pure contaminant solubility in near‐critical CO 2 and crossover phenomena in SCF CO 2 ). These results have been accurately modeled using a hardsphere, perturbation‐theory‐based Carnahan‐Starling‐DeSantis‐Redlich‐Kwong equation of state and simple van der Waals mixing rules.