As the Hanford site undergoes remediation, it is noted that significant economies could be realized by minimizing the amount of aluminum deposited in High-Level Waste glass. Though such a step is not planned, an acidic scrub of the Hanford sludge could enhance Al removal. It is likely that the resulting Al(NO 3) 3 solution would contain measurable amounts of transuranic elements, thus the solution might require some secondary treatment to remove TRU contamination. Thus far, extraction chromatography (EXC) has shown promise [1] as an alternative to a liquid-liquid remediation of the Hanford site. Previous EXC studies have shown >99% of the Eu can be extracted from simulated Al/Cr waste. This study continues an examination of a hypothetical secondary cleanup of the waste by studying the removal of UO 2 2+ , NpO 2 + , NpO 2 2+ and Th 4+ from using tri-n-octyl phospine oxide (TOPO) impregnated XAD7 resins. Neptunium was held in the V and VI oxidation states using ascorbic acid and chromate, respectively. Initial results show extraction following classical metal recovery trends, wherein an increased Z eff correlates with increased distribution of the metal into the organic resin phase. The uptake of Eu 3+ (representative of An 3+) on a column of the same material was also investigated. Uptake kinetics were improved by wetting the TOPO-XAD7 resin with n-dodecane (TOPO-XAD7n). The presence of n-dodecane also provided consistency between batch mode and column mode metal recovery. Preliminary data show >99% recovery of metal ions with a Z eff > 3 under various simulated conditions.

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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.

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