Mechanism of the ion-exchange separation of mixtures of rare earth elements during elution with solutions of nitrilotriacetic acid

Abstract

1. The composition of complex compounds of the REE, formed during their elution from an ion-exchange resin by solutions of salts of nitrilotriacetic acid, was studied. 2. The separation of mixtures of REE is accomplished on account of mono- and dinitrilotriacetates. In the adsorption zone, mononitrilotriacetates LnX predominate, while in the zone of separation, saturated with NH4+ ions or “retaining ions” (Cu2+), the mononitrilotriacetates are converted to dinitrilotriacetates [LnX2]3−. 3. When the resin of the zone of separation is saturated with Cu2+ ions, there is practically no contact between the REE nitrilotriacetates and the resin in the Cu2+-form. The retaining action of Cu2+ is associated with the formation of a layer of resin with an increased content of hydrogen ions between the zone of CuR2 and the zone of LnR3.