INVESTIGATION OF SYNERGISTIC EXTRACTION MECHANISM OF RARE EARTH ELEMENTS(Ⅲ) WITH HEHEHP AND PMBP

The synergistic extraction of rare earth elements(Ⅲ) including La, Nd, Gd, Er, Yb, Lu and Y from aqueous mineral acid (H2SO4, HC1, HNO3 ) with binary system 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEH-EHP, HL) and 1_phenyl-3-methyl_4-benzoyl-pyrazolone-5 (PMBP, HA) in toluene has been investigated. The compositions of the synergistic extracting complexes and the mechanism of the synergistic extraction have been determined by the methods of slope and constant molarity. The synergistic extracting complexes Nd(HL2)A2 and Yb(HL2)2A have been demonstrated. The synergistic extraction reactions of rare earth elements (Ⅲ) have been proposed as follows.The equilibrium constants and the thermodynamic functions of the synergistic reactions have been calculated. The IR and NMR of the synergistic extracting complexes have been studied as well.