Abstract: The transfer of trivalent europium ion in a liquid surfactant membrane system was investigsted in order to clarify the characteristics of liquid membrane separation process and the availability of this technique for recovering trivalent lanthanides and actinides. The membrane phase consists of kerosene (solvent), Span-80 (surfactant) and di-(2-ethylhexyl) phosphoric acid (HDEHP, carrier). The internal phase is dilute nitric acid and the external phase is aqueous solution containing Eu(NO3)3 buffered by HAc-NaAc. Results show that the transfer rate of europium in this system is rather high and the recovery of europium may be higher than 99%. A multilayer structure model for emulsion globuls and the equations describing the change of effective membrane thickness during mass transfer are suggested. The resulting mass transfer flux equation is as follows: where Co: concentration of Eu3+, at t = t0, Ct: concentration of Eu3+, at t = t, V : volume of external phase, F: total mass transfer surface area, CH: initial acid concentration in internal phase, C : carrier concentration in membrane phase, D: diffusion coefficient of Eu3+-HDEHP complex in membrane phase, Experimental data show that l-(Ct/Co) is actually a linear function of and D calculated is about 1.1×10-6 cm2/s.