Process for separation of the rare earths by solvent extraction

Claim 1

In the method for separating rare earth and yttrium elements from each other by contacting an aqueous mineral acid feed solution containing a plurality of rare earths and yttrium with a plurality of solutions of an organic extractant in a water-immiscible organic diluent whereby the elements having the highest atomic number are preferentially extracted from the feed solution and the extractability of the elements decreases with decreasing order of atomic number, contacting the extractant with a plurality of aqueous mineral acid scrub solutions whereby the rare earths are separated into fractions in the aqueous and organic solutions according to their atomic number, the lower atomic number elements preferentially concentrating in the scrub solutions in decreasing order of their atomic number and the higher atomic number elements preferentially concentrating in the organic extractant solutions in increasing order of their atomic number and collecting each fraction separately, the improvement wherein the feed and scrub solutions are 0.1 to 2.0 M in a nonoxidizing mineral acid and the organic extractant is up to 1.0 F di(2-ethylhexyl) mono-thiophosphoric acid in a water-immiscible organic diluent whereby higher concentrations of rare earth and yttrium elements are extracted from the feed solution without forming an insoluble polymer with the extractant.