Separation of rare earths in chloride media by synergistic solvent extraction with mixture of HEHAMP and CA12 and stripping with HCl

Abstract

The synergistic extraction of rare earths (REs) from chloride media by a mixture of two extractants 2-ethylhexylaminomethyl phosphonic acid mono-2-ethylhexyl ester (HEHAMP, HA) and sec-octylphenoxy acetic acid (CA12, HB) was investigated. A remarkable positive synergistic effect was observed at the molar ratio of HEHAMP to CA12 being of 2:3. The extraction of REs was found to be a cation exchange process and the extracted species of Yb3+ was determined as YbCl2HAB. The separation factors (SF) of adjacent heavy REs, i.e. SFYb/Tm and SFLu/Yb, for the mixtures were 2.50 and 1.63, which were much higher than those of the sole HEHAMP and the sole CA12 system. In additional, the values of SFYb/Y and SFLu/Y were 7.17 and 11.14, respectively, which were higher than those of other reported synergistic systems and those of the sole HEHAEP or CA12 system, suggesting that the mixture of HEHAMP and CA12 is a potential synergistic extraction system for the separation of heavy REs and/or Y(III) from other heavy REs. A cascade extraction process for the separation of Y(III) from yttrium-enriched REs feed using the synergistic extraction system was developed, which are superior to sole CA12 system. The Y2O3 product with a purity of 99.4% was obtained by 8 extraction stages and 5 scrubbing stages.