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New unsymmetrical diglycolamides (UDGAs), N, N-di-butyl- N′, N′-di-dodecyl-3-oxapentane-1,5-diamide (C12-C4), N, N-di-dodecyl- N′, N′-di-hexyl-3-oxapentane-1,5-diamide (C12-C6), N, N-di-decyl- N′, N′-di-dodecyl-3-oxapentane-1,5-diamide (C12-C10) have been synthesized, and evaluated for the separation of americium(III) and europium(III) from nitric acid medium. The extraction behavior of Am(III), Eu(III), and Sr(II) in a solution of these UDGAs in n-dodecane was studied as a function of concentration of nitric acid in the aqueous phase. The distribution ratio of Am(III) and Eu(III) increased with increase in the concentration of nitric acid. The third phase formation behavior of nitric acid and neodymium(III) in 0.1 M UDGA/ n-dodecane was studied. The third phase formation was not observed in all these UDGAs in n-dodecane (0.1 M), when the concentration of Nd(III) was ∼ 500 mM in 3-4 M nitric acid. The stoichiometry of Am(III)-UDGA was determined from the slope analysis of the extraction data, which indicated the formation of 1:3 complex in all cases. Our studies revealed that the UDGA ligands with dodecyl group attached to one amidic nitrogen atom is inevitable for preventing third phase formation and the alkyl group at the other amidic nitrogen can be varied from butyl to decyl group for obtaining efficient extraction of trivalent actinides from high-level nuclear waste. [ABSTRACT FROM AUTHOR]

Abstract: A new unsymmetrical diglycolamide, N,N-di-dodecyl-N′,N′-di-2-ethylhexyl-3-oxapentane-1,5-diamide trivially known as di-dodecyl-di-ethylhexyl diglycolamide (D3DEHDGA) has been synthesized, and characterized by 1H and 13C NMR, mass, and IR spectroscopic techniques. D3DEHDGA has been evaluated for the removal of long-term hazardous metal ions from high-level liquid waste (HLLW) originating from reprocessing of fast reactor spent nuclear fuel. The extraction behaviour of radiotoxic metal ions such as Am(III), U(VI), Eu(III), Ru(III), Sr(II), Ba(II), Sb(III), and Cs(I) was studied from nitric acid as well as from simulated HLLW in 0.1M D3DEHDGA/n-dodecane. The stoichiometry of D3DEHDGA-Am(III) was determined by linear regression of extraction data. Third phase formation behaviour of D3DEHDGA/n-dodecane with nitric acid and trivalent metal ion, Nd(III), was investigated. Higher limiting organic concentration and critical aqueous concentration of trivalent metal ion, complete extraction of trivalent actinides, and negligible extraction of unwanted metal ions, make D3DEHDGA a promising candidate for partitioning of toxic trivalent actinides from HLLW. [Copyright &y& Elsevier]