Properties and applications of cryptand-22 surfactant for ion transport and ion extraction

A non-ionic cryptand-22 surfactant consisting of a macrocyclic cryptand-22 polar head and a long paraffinic chain (C10W21-Cryptand-22) was synthesized and characterized. The critical micellar concentration (CMC) of the crypta nd surfactant in ROH/H2O mixed solvent was determined by the pyrene fluores cence probe method. In general, the cmc of the cryptand surfactant increase d upon decreasing the polarity of the surfactant solution. The cryptand sur factant also can behave as a pseudo cationic surfactant by protonation of c ryptand-22 or complexation with metal ions. Effects of protonation and meta l ions on the cmc of the cryptand surfactant were investigated. A prelimina ry application of the cryptand surfactant as an ion-transport carrier for m etal ions, e.g., Li+, Na+, K+ and Sr2+, through an organic liquid-membrane was studied. The transport ability of the cryptand surfactant for these met al ions was in the order: K+ greater than or equal to Na+ > Li+ > Sr2+. A c omparison of the ion-transport ability of the cryptand surfactant with othe r macrocyclic polyethers, e.g., dibenzo-18-crown-6, 18-crown-6 and benzo-15 -crown-5, was studied and discussed. Among these macrocyclic polyethers, th e cryptand surfactant was the best ion-transport carrier for Na+, Li+ and S r2+ ions. Furthermore, a foam extraction system using the cryptand surfacta nt to extract the cupric ion was also investigated.