Studies on Selective Separation of Metal Ions with Ion Exchange Materials by Immobilizing Extractant

Ion exchange materials of environmentally friendly having high selectivity for metal ions have been investigated, as such (1) preparation of coated solvent impregnated resin, to prevent from leakage of extractant, and its application to selective separation of metal ions and (2) novel ion exchange material based on photo-swing adsorption and its application to adsorptive separation of rare earth metals. The leakage of the extractant from the solvent impregnated resin, during operation, can be successfully suppressed by coating the solvent impregnated resin by cross-linked water-soluble polymer, although adsorption capacity is slightly decreased. Selective separation of rare earth metals can be achieved with column mode operation using the coated solvent impregnated resin. Novel photo-swing ion exchange material is also developed to decrease in the amount of eluent solution. Extractant and carbon nanotube, as molecular heater, are immobilized on thermosensitive polymer. The adsorption amount can be controlled by photo-irradiation, since phase transition of the thermosensitive polymer is occurred by the photo-irradiation. The difference in the adsorption amount, with and without photo-irradiation, can be increased by decrease in the cross-linking, although the immobilization of the carbon nanotube becomes difficult. The immobilization of the carbon nanotube can be improved by introducing pyrene group on the ion exchange material. Separation ability of several combinations of rare earth metals is increased by photo-irradiation.