N,N,N^′,N^′-Tetra-Methyl-3-Oxy-Pentane-1,5-Diamide (TMPDA): A Promising Back Extractant for Ln(III) and Zr(IV)

Water-soluble oxa-diamide ligand, N,N,N^′,N^′-tetra-methyl-3-oxy-pentane-1,5-diamid (TMPDA) has been synthesized and purified. Its crystal structure, melting point, decomposition temperature, solubilities in aqueous phase and organic phase, distribution ratio between aqueous and organic phase, etc. are reported. The effect of TMPDA concentration in aqueous phase and HNO₃ concentration in the equilibrium aqueous phase on the extraction efficiency of La(III), Ce(III), Pr(III), Nd(III), Zr(IV), Fe(III), Y(III), Mo(VI), Ru(III) and Pd(II) by 30% TRPO/kerosene have been studied. The results indicate that TMPDA dissolve well in aqueous phase but almost insoluble in kerosene or 30%TRPO/kerosene in the bi-phase system. It can effectively reduce the extraction of Ln(III), Y(III) and Zr(IV) into 30%TRPO/kerosene at a moderate acid system (0.24mol/L∼0.27mol/L HNO₃). TMPDA is a promising stripping agent for Ln(III), Y(III) and Zr(IV) from loaded TRPO.