No abstract

A tetramethylmalonamide-functionalized resin (TMMA resin) has been developed and investigated for its ability to separate trivalent, tetravalent, and hexavalent actinide elements. As a fundamental study of the extraction mechanism and to design a chromatographic separation scheme, distribution coefficients (K d ) for partitioning of Eu(III), Th(IV), U(VI), and Am(III) onto the resin from HNO 3 , NaNO 3 , HCl, and NaCl solutions have been determined. The partitioning of HNO 3 onto the resin was also evaluated. The order of the K d values was Th(IV) > U(VI) > Am(III) = Eu(III) in all tested solutions. The competition between metal extraction and HNO 3 extraction was confirmed by the extraction data and FT-IR spectra. The loading capacities of Eu(NO 3 ) 3 and UO 2 (NO 3 ) 2 at 3 M HNO 3 , determined by a dynamic method with TMMA resin (TMMA in the resin was 2.05 mmol/g), were 0.83 mmol/g and 1.6 mmol/g, respectively, implying that M:TMMA stoichiometry was 1:2 for Eu(III) and 1:1 for U. Because the K d values for Th(IV) and U(VI) were greater than 100 in all solutions tested, the influence of organic acids on the K d values of Th(IV) and U(VI) from 3 M and 0.01 M HNO 3 solutions was studied to identify potential stripping agents. The effects of Na, Al, K, Ca, Cr, Ni, and Fe (potential constituents of low-level radioactive waste) on the K d values of Am(III) were also studied. Although the K d values for Am(III) decreased in the presence of 0.01 M Fe(III), the influence of the other ions was negligible. Based on these fundamental experimental results, an extractive chromatographic scheme for actinide isolation was designed and demonstrated.