Synergistic extraction of rare earths by mixture of HDEHP and HEH/EHP in sulfuric acid medium

The extraction of RE(Ⅲ) (RE=La, Nd, Sm, Gd) in sulfuric acid medium using the mixture of HDEHP(H2B2) and HEH/EHP(H2L2) was investigated. The synergistic enhancement coefficient(R) was calculated for La (1.96), Nd(3.52), Sm(5.96), and Gd(5.71), respectively,at pH=2.0, and it was seen that the R increased with the increase of aqueous quilibrium pH. The configuration of the extracted complexes was considered to be RE(SO4)xH2x(HB2)3 with HDEHP, RE(SO4)xH2x(HL2)3 with HEH/EHP, and RE(HB2)2(HL2) with their mixture as the extractant with the slope method. The equilibrium constants and stability constants were calculated. A cation exchange mechanism was pro-posed as well.