Design of ion-exchange resins selective of caesium. Synergistic effect of macrocycle in phenolic resins

The extraction of caesium by resorcinol based resins was investigated. At h igh hydroxide concentration ([OH-] = 0.15 M), the alkali-metal cations' sor ption selectivity (determined in competitive extraction system) for resorci nol resins was found to be Cs+ > Li+ > Rb+ > K+ > Na+, whereas at pH 7 this selectivity was found to be Cs+ > Rb+ > K+ >> Na+ approximate to Li+. Diff erent mechanisms of ion exchange occurring in these phenolic resins can exp lain this selectivity series. Then different macrocycles were incorporated in the resins. The ionoselective properties of these new ion-exchange resin s are strongly influenced by the nature of the crosslinker. The presence of macrocycles lead to an improvement of selectivity towards caesium in relat ion with the size of the macrocycles introduced.