Extraction kinetics of mixed rare earth elements with bifunctional ionic liquid using a constant interfacial area cell

Abstract

As a bifunctional ionic liquid used for the extraction of yttrium and heavy rare earth elements (REEs), [methyltrioctyl ammonium][(2,6-dimethylheptyl) phenoxy acetic acid] ([N₁₈₈₈][POAA]) has been synthesized in this paper. The extraction kinetics of REEs including La–Lu plus Y except Pm with [N₁₈₈₈][POAA] using a constant interfacial area cell were reported. Comparing with the conventional (2,6-dimethylheptyl) phenoxy acetic acid (HPOAA) extraction system, the forward extraction rate (k_ao, mm s⁻¹) of heavy REEs in the [N₁₈₈₈][POAA] extraction system increased significantly with an improvement of 8.44 times for yttrium. The effect of stirring speed on the extraction rate of mixed REEs was studied and 300 rpm was suggested to ensure the extraction regimes were chemical reaction-controlled. The effect of temperature was studied and the extraction reaction was controlled by chemical reaction when the temperature was below 298 K. The effect of specific interfacial area was also evaluated which indicated that the bulk phase was the reaction zone. The average extraction rate equation of REEs has also been obtained as: −d[RE]_(o)/dt = 0.141[RECl₃]([N₁₈₈₈][POAA]).