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

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 Yb 3+ was determined as YbCl 2 HAB. The separation factors ( SF ) of adjacent heavy REs, i.e. SF Yb/Tm and SF Lu/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 SF Yb/Y and SF Lu/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 Y 2 O 3 product with a purity of 99.4% was obtained by 8 extraction stages and 5 scrubbing stages. • The mixtures of HEHAMP and CA12 exhibit a remarkable synergistic effect toward the extraction of rare earths. • Maximum synergistic effect was obtained with the HEHAMP and CA12 molar ratio being 2:3. • The separation performance for heavy REs and Y was better than that of the sole HEHAMP systems. • The synergistic complex was determined to be YbCl 2 HAB.