Evaluation of the malonamide substructure with respect to binding site preorganization and complementarity for lanthanide metal ions suggests a new ligand architecture specifically designed to enhance lanthanide ion affinity. Consideration of conformational reorganization, restricted bond rotation, and donor group orientation suggests that typical malonamide structures, for example, N,N,N'N'-tetrahexylpropane-1,3-diamide (1), N,N'-dibutyl-N,N'-dimethyl-2-tetradecylpropane-1,3-diamide (2), or N,N,N'N'-tetramethylpropane-1,3-diamide (6), are poorly organized for metal ion complexation. Molecular mechanics analyses show that the unfavorable enthalpic and entropic terms are eliminated by the use of the novel bicyclic architecture found in 3,9-diaza-3,9-dimethylbicyclo[4.4.0]decane-2,10-dione (7). Diamide 7 was prepared, and the X-ray crystal structure of the complex [Eu(7)(2)(NO(3))(3)] exhibits the same chelate conformation predicted by the molecular mechanics model. A hydrophobic derivative, 3,9-diaza-3,9-dioctylbicyclo[4.4.0]decane-2,10-dione (8), was prepared, and solvent extraction studies reveal that the preorganized architecture of 8 gives a dramatic enhancement in binding affinity, exhibiting Eu(3+) distribution coefficients that are 7 orders of magnitude larger than a typical malonamide ligand, 1.

A new bicyclic diamide compound, 3,9-diaza-3,9-dioctylbicyclo[4.4.0]decane-2,10-dione (1) has been prepared, and its affinity for Eu 3þ and Am 3þ has been explored using liquid-liquid extraction methods. Molecular mechanics calculations have shown that the two amide oxygen atoms in 1 should be ideally situated for binding to trivalent actinide or lanthanide ions and should form strong complexes. The data in this report support this hypothesis. As determined by liquid-liquid extraction, the affinity of 1 for Eu 3þ is on the order of 10 7 times greater than previously investigated malonamides. The extraction behavior for Am 3þ is similar to that of Eu 3þ .

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This report describes the caustic leaching test conducted on Hanford Tank T-110 sludge during FY 2002 at the Pacific Northwest National Laboratory. The data presented here can be used to develop the baseline and alternative flowsheets for pretreating Hanford tank sludge. The U.S. Department of Energy funded the work through the Efficient Separations and Processing Crosscutting Program (ESP; EM-50). The T-110 sludge sample was first subjected to washing with dilute sodium hydroxide solution at ambient temperature. Following the dilute hydroxide washing, several aliquots of the washed solids were taken for leaching tests. The washed solids were subjected to leaching with 1, 3, or 5 M NaOH at 60, 80, or 100°C for up to 168 h. The leachates were sampled at 4, 8, 24, 72, and 168 h. The leached solids were dried to constant mass at 105°C and then analyzed. Bismuth, Fe, Na, P, and Si are the dominant elements present in the T-110 sludge. As expected, Na is largely (> 90%) removed by dilute hydroxide washing. However, dilute hydroxide washing is ineffectual at removing Bi, Fe, or Si. For this particular sludge, the behavior of P is of major concern due to the relatively low tolerance for this element in the high-level waste (HLW) immobilization process and the high concentration of P in the waste. Only 33% of the P was removed by dilute hydroxide washing, resulting in washed solids that were 8.8 wt% P. This is presumably because the P is present as bismuth phosphate in the T-110 solids. More rigorous pretreatment (e.g., caustic leaching) will be required to remove enough P so that it is not a limiting component in the sludge solids. The minor sludge component, Cr, can also adversely affect the HLW immobilization process. The Cr in the T-110 sludge was largely insoluble in 0.01 M NaOH, with only 3% being removed by dilute hydroxide washing. The solution obtained by washing the T-110 solids with dilute hydroxide could likely be immobilized as a Class A low-level waste (LLW), even without removing 137 Cs. The work presented here indicates caustic leaching to be a very effective method for pretreating Hanford Tank T-110 sludge, primarily because this method essentially quantitatively removes P from the water-washed T-110 solids. Assuming a P 2 O 5 limit of 3 wt% in the immobilized high-level waste (IHLW) glass, it is estimated that caustic leaching will result in an ~80% reduction in the IHLW mass. Unlike high-Al tanks (see for example, Lumetta et al. 2001), relatively mild leaching conditions (1 M NaOH at 60°C) should sufficiently remove P from the T-110 solids. However, more rigorous leaching conditions (or oxidative leaching) may be needed to avoid encountering the Cr limit in the glass formulation. The leaching of P from the sludge solids is rapid and largely independent of temperature and NaOH concentration. On the other hand, the leaching of Cr is much slower and is highly dependent on temperature and NaOH concentration. Some of the caustic-leaching solutions contained significant concentrations of transuranic (TRU) el...

SummaryThis report describes experiments conducted to demonstrate the proof-of-principle of a method to recover NaOH from Hanford tank sludge leaching solutions. Aqueous solutions generated from leaching actual Hanford tank waste solids were used. The process involves neutralization of a lipophilic weak acid (t-octylphenol was used in these experiments) by reaction with NaOH in the aqueous phase. This results in the transfer of Na into the organic phase. Contacting with water reverses this process, reprotonating the lipophilic weak acid and transferring Na back into the aqueous phase as NaOH.The work described here confirms the potential application of solvent extraction to recover and recycle NaOH from solutions generated by leaching Hanford tank sludges. Solutions obtained by leaching sludges from Tanks S-110 and T-110 were used in this work. It was demonstrated that Na + is transferred from caustic leaching solution to the organic phase when contacted with t-octylphenol solutions. This was accompanied by a concomitant decrease in the aqueous-phase hydroxide ion concentration. Seventy to 80% of the extracted Na was recovered by 3 to 4 sequential contacts of the organic phase with water. Cesium was co-extracted by the procedure, but Al and Cr remained in the feed stream.The results of this study revealed several areas that will require further investigation before the technology can be implemented.