Aqueous polymeric solutions as environmentally benign liquid liquid extraction media

Several liquid-phase extraction technologies employing environmentally benign phase- or micelle-forming polymers in aqueous solution have the potential to replace volatile organic compounds in classical solvent extraction technologies. The examples reviewed here include aqueous biphasic system's, cloud-point extraction, micellar extraction, and thermoseparating polymer systems. The apparent similarities of these systems, their phase-separating properties, and their ability to solubilize a wide variety of solutes ranging from metal ions, organic compounds, and biologicals are discussed. Some comparative data from the literature whereby the solvating power of these systems may be compared to traditional solvents are presented along with new data on the polarity of the phases in typical aqueous biphasic systems. The need for additional comparative data in this area and the need to demonstrate the validity of the approach in operational processes are emphasized. A "toolbox" approach to implementing environmentally benign polymers in clean separations science and technology could lead to new and better solvent extraction systems.