Design of ionic liquids for homogeneous liquid-liquid extraction and aqueous biphasic extraction of metal ions

Ionic liquids (ILs) are solvents that consist entirely of ions. They have special properties such as a negligible vapor pressure which makes them an excellent environmentally friendly alternative to organic solvents. Ionic liquids can be divided into hydrophilic ionic liquids which are totally miscible with water and hydrophobic ionic liquids which are immiscible with water. Ionic liquids can also show a temperature dependent miscibility with water. Some IL/solvent mixtures have an upper critical solution temperature (UCST). They form one homogeneous phase above the UCST and phase-separate below this temperature. Other IL/solvent mixtures have a lower critical solution temperature (LCST). They form one homogeneous phase below the LCST and phase-separate above this temperature. This project is about the development of solvent extraction systems for the separation of metal ions, based on non-fluorinated ionic liquids showing temperature dependent miscibility with water. Intense stirring can be avoided during extraction by the formation of a homogeneous phase above (below) the UCST (LCST). In the homogeneous phase, a fast reaction between the metal ion and the extraction agent can take place. Upon cooling, phase separation occurs with transfer of the metal complex to the IL phase. Such as separation process is called homogeneous liquid-liquid extraction (HLLE). The ionic liquid solvent extraction systems will be used for the recovery and separation of rare earths and other critical metals.status: publishe