Improvements relating to processes for the separation of components of mixtures containing rare earths and, if desired, yttrium

摘要

Ethylenediamine tetraacetic acid is recovered from eluates from ion exchange columns containing complexes of said acid with rare earth metals, yttrium, and cadmium or zinc by acidifying with sufficient hydrochloric, nitric or sulphuric acid to provide an excess of at least 0,07 moles/1., agitating for 8-16 hours and altering. From the filtrate thus produced, rare earth metal and yttrium oxalates may be precipitated.ALSO:Individual rare earth metals and yttrium are partially separated either (a) by absorbing the metals in a cation exchange resin bed, eluting the bed with a solution of a watersoluble salt of an aminopolyacetic acid, passing the eluate through a bed of cation exchange resin in the zinc or cadmium form and collecting successive fractions or (b) by charging a cation exchange resin bed with a solution containing the mixture to be separated together with zinc or cadmium salts, eluting the bed with the above-mentioned eluting agent and collecting successive fractions. Satisfactory results are obtained with a ratio of Zn or Cd:rare earths of 5:1 to 1:3. Specified complexing agents are ethylenediamine tetraacetic acid (ammonium or sodium salt), nitrilotriaceticacid, hydroxyethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid and diaminocyclohexanetetraacetic acid. The preferred resins are sulphonated copolymers of styrene and divinyl benzene having a cross linkage of 4% or less. Specified metals are Y and La, Pr, Nd, Sm, Dy, Ho, Er, Tm and Yb. Ethylenediaminetetraacetic acid may be recovered from the eluate by adding hydrochloric, nitric or sulphuric acid. The metals may be recovered from the resultant solutions as carbonates, fluorides, oxalates or hydroxides; or said solutions may be fed as such, or after mixing with the original feed solution, to cation exchange column for further fractionation.