Separation of Rare Earth Elements from Base Metals in Concentrated HNO₃, H₂SO₄ and HCl Solutions with Diglycolamide

抄録

The separation of Nd(III) and Dy(III) from Fe(III) and Ni(II) in relatively high concentrations of HNO₃, HCl and H₂SO₄ solutions (0.1 – 7 M) was investigated using with 0.1 M N,N′-dimethyl-N,N′-di-n-octyl-diglycolamide (MODGA) in 80 vol% n-dodecane—20 vol% 2-ethylhexanol. In all systems, the extraction percentage (E%) value for Dy(III) is higher than that for Nd(III), and the E% values for Nd(III) and Dy(III) increase with an increase in the acid concentration. The extracted Nd(III) and Dy(III) in the organic phase can be back-extracted using distilled water. The back E% is dependent on the acid concentration in the forward extraction. Both Fe(III) and Ni(II) are poorly extracted in all systems, although Fe(III) is extracted at >2 M HCl. Therefore, Nd(III) and Dy(III) are readily separated from Fe(III) and Ni(II) in the HNO₃ and H₂SO₄ systems. The separation of Nd(III) from Dy(III) is effectively performed in the forward extraction reaction at ~1 M HCl and ~1 M H₂SO₄ and the back extraction of Nd(III) and Dy(III) from the organic phase produced by extraction from the ~1 M HNO₃ solution.