Abstract: The separation of Sm³⁺ and Gd³⁺ by liquid membranes system containing TAP and N263 co-extraction mobile carrier was studied. The effect of several factors on transport of Sm³⁺ and Gd³⁺ was examined. N263 can be dissolved in kerosene when TBP was used as oil adjusting agents. So kerosene may take the place of some aromatic diluents. On the other hand, a co-extraction effect was found between N263 and TBP in membrane process. Instead of using dilute HNO₃ as stripping agent, dilute NH₄NO₃ was used to be an internal aqueous phase in the experiment. The stripping result of dilute NH₄NO₃ for Sm³⁺ and Gd³⁺ was similar to that of dilute HNO₃ as their concentrations were all in 0. 01～0.5 mol/L. When the membrane system of N263-TBP LMA-1-kerosene (oil phase) and NH₄NO₃ (internal aqueous phase) was applied, the transport rate decreased with the increase of atomic number of rare earth, and the system selectivity for Sm³⁺ and Gd³⁺ is better than N263 system.

Key words: N263, TBP, Liquid membrane, Samarium, Gadolinium