Extraction and transport of lithium ion by a crown ether-alkylphosphoric acid system [1]

Mixed carrier systems composed of crown ethers and alkylphosphoric acids have been studied as lithium ionophores using a solvent extraction technique and in transport across liquid membranes. The combination of dibenzo-14-crown-4 and bis(2-ethylhexyl) phosphoric acid showed a synergistic enhancement on both lithium ion selectivity and transport rate. The synergistic effects depended strongly upon crown ether structure and the enhancement was observed only when the metal cation corresponded to the crown ether's cavity diameter. Complex formation in the organic phase was assessed by use of FAB-mass spectrometry.