Quantitative extraction of aqueous alkali metal ions using supercritical carbon dioxide and polyethylene glycol ligands
Abstract
Quantitative extraction (30–70%) of alkali metal ions (K+, Na+: 1.7 × 10−4 mol dm−3) from aqueous solutions with supercritical carbon dioxide (40 °C, 10–18 MPa) could be achieved using glymes (triethylene glycol dimethyl ether (triglyme: 3G), tetraethylene glycol dimethyl ether (tetraglyme: 4G)) and the addition of pentadecafluoro-n-octanoic acid (HPFOA) that supplies a CO2-philic counter ion and makes the metal–ligand complex soluble in the CO2 solvent via counter ion exchange.