Separation of Nd3+ and Fe3+ by non-equilibrium solvent extraction using an annular centrifugal contactor

• Non-equilibrium solvent extraction is used for the separation of Nd3+ and Fe3+.
• The annular centrifugal contactor is used for non-equilibrium solvent extraction.
• The extraction stage efficiency (EA) of Nd3+ is much higher than that of Fe3+.
• Effects of some parameters on the EA of Nd3+ are different from those on the EA of Fe3+.

A TRPO (tri-alkyl phosphine oxide) process with 30% TRPO–kerosene as extractant for the removal of actinides from high level liquid waste (HLLW) has been developed in China. It is important to decrease the extraction of Fe to prevent third phase formation in the TRPO process. In this paper, the separation of Nd3+ and Fe3+ with 30% TRPO–kerosene from nitric acid solution by non-equilibrium solvent extraction using a 20-mm-diam. annular centrifugal contactor (ACC) was investigated. The extraction stage efficiency (EA) of Nd3+ was more than 95%, much higher than that of Fe3+. The EA of Nd3+ and Fe3+ varied with the changes of the total flow rate, the flow ratio (aqueous phase/organic phase, A/O), the rotor speed, the width of the annular gap, and the height of the clearance, but the effects of these parameters on the EA of Nd3+ is different from that of Fe3+. These results show that non-equilibrium solvent extraction using ACCs can be used for the separation of Nd3+ and Fe3+ with 30% TRPO–kerosene from nitric acid solution. Accordingly, non-equilibrium solvent extraction using ACCs can also be used for the separation of trivalent actinides and Fe3+ with 30% TRPO–kerosene, based on the fact that the extraction behavior of trivalent actinides is similar to that of Nd3+ with 30% TRPO–kerosene from nitric acid solution, and thus avoiding third phase formation in the TRPO process.