Synergistic extraction of heavy rare earths by mixture of α-aminophosphonic acid HEHAMP and HEHEHP

Synergistic extraction of heavy rare earths (REs) were investigated in chloride media by the mixture of (2-ethylhexylamino) methyl phosphonic acid mono-2-ethylhexyl ester (HEHAMP) and 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (HEHEHP). The maximum synergistic enhancement co-efficients (R) of Lu, Yb, Tm, Er, Y and Ho are 2.89, 2.76, 2.54, 2.14, 2.14 and 2.06, respectively, when the mole fraction X-HEHAMP is 0.5. The synergistic separation factors of the heavy REs are obtained (beta(Y/Ho) = 1.31, beta(Er/Y) = 1.61, beta(Tm/Er) = 1.78, beta(Yb/Tm) = 1.76, beta(Lu/Yb) = 1.20). The extracted complex is determined to be RE[H(EHAMP)(2)][H(EHEHP)(2)](2) by the slope analysis method. The loading capacities of the mixtures consisting of 15% HEHAMP and 15% HEHEHP for Y and Lu are about 26.59 g/L (Yb2O3) and 27.25 g/L (Lu2O3), respectively. (C) 2019 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.