Procédé pour le contrôle du pH lors de la séparation des terres rares par chromatographie sur échangeurs d’ions

Abstract

(NH₄)₃H-EDTA-solutions of relatively high concentration can be used for the separation of the rare earths by complex-elution on ion-exchangers. The available acidity of the elutriant is determined acidimetrically in the présence of zinc sulfate; calculated amounts of HCOONH₄ or CH₃COONH₄ are added to convert the hydrogen ion liberated by the exchange reaction to the corresponding acids and to buffer the resulting solution to pH ~ 3 (for the separation of the yttrium group) or ~ 4 (for the cerium group).