Selective separation of rare earth metals by solvent extraction in the presence of new hydrophilic chelating polymers functionalized with ethylenediaminetetraacetic acid .1. Development of new hydrophilic chelating polymers and their adsorption properties for rare earth metals

New hydrophilic chelating polymers were synthesized by introducing ethylenediaminetetraacetic acid (EDTA) onto water-soluble polyallylamine. The selective separation of rare earth metals by solvent extraction including these chelating polymers in the aqueous phase is the goal of this work. The polymers were characterized by IR analysis, elemental analysis, gel permeation chromatography (GPC) measurement, and pH titration. Two kinds of polymers with different solubilities in water were produced using different solvents. Both polymers were naturally precipitated in the presence of rare earth metals. This suggests that in the solvent extraction system including these chelating polymers, the recovery of the polymers is easy. Adsorption properties of Y3+ and Er3+ on these polymers were also investigated. The separation properties by adsorption on the polymers were comparable to those by EDTA. The chelating polymers had the characteristics that their separation factors decreased by adsorption and the total amount adsorbed increasing pH or initial metal concentrations, although in the presence of EDTA these properties were found to be almost constant.