Synergistic extraction and separation of rare earths from chloride medium by the mixture of HEHAPP and D2EHPA

A binary mixture of α-aminophosphonic acid extractant 2-ethylhexyl-3-(2-ethylhexylamino)pentan-3-yl-phosphonic acid (HEHAPP, H2A2) and di-(2-ethylhexyl) phosphoric acid (D2EHPA, H2B2) in n-heptane was employed for the extraction and separation of rare earths (REs) from chloride medium. A remarkable synergistic effect was observed in the Lu(III) extraction by the mixture. The extracted species of Lu(III) was determined as LuH4Cl2A3B2. The separation factors of adjacent heavy REs, i.e. SFEr/Ho, SFTm/Er, SFYb/Tm and SFLu/Yb, were of 1.45, 2.58, 2.77 and 1.77, which were much higher than those for other reported synergistic systems, suggesting that the mixture of HEHAPP and D2EHPA is a potential synergistic extraction system for the separation of heavy REs.