Substituted malonamides as extractants for partitioning of actinides from nuclear waste solutions

• Published in: Waste management (Elmsford) 1998-01, Vol.18 (2), p.125-133
• Main Authors: Mahajan, G.R., Prabhu, D.R., Manchanda, V.K., Badheka, L.P.
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemistry; Exact sciences and technology; Inorganic chemistry and origins of life; Kinetics and mechanism of reactions; Pollution; Radioactive wastes; Wastes
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/S0956-053X(98)00015-4

Pentaalkyl malonamides are suggested as alternatives to organophosphorous reagents for the extraction of actinides from high level liquid waste generated during the reprocessing of irradiated fuels. With a view to study the extraction behaviour of these actinides from nitric acid medium, four diamides namely (1) N,N,N′,N′-tetrabutyl undecyl malonamide (TBUDMA), (2) N,N,N′,N′-tetrabutyl tetradecyl malonamide (TBTDMA), (3) N,N′-dimethyl- N,N′-dibutyl undecyl malonamide (DMDBUDMA) and (4) N,N′-dimethyl- N,N′-dibutyl tetradecyl malonamide (DMDBTDMA) were prepared by substitution on the basic skeletons of N,N,N′,N′-tetraalkyl-2-alkyl malonamides. The substituted diamides showed good extractability towards Am, Pu, Np and U into n-dodecane from nitric acid solutions of concentrations ranging from 3 to 8 M except for DMDBUDMA which showed third phase formation beyond 2 M HNO 3. Extraction maxima for Am with TBUDMA and TBTDMA were seen at 6–7 M whereas DMDBTDMA showed maximum extraction at 5 M nitric acid. Am(III) and Pu(IV) extracted as trisolvates whereas U(VI) was extracted as disolvate. Distribution behaviour of fission products using DMDBTDMA was also investigated. DMDBTDMA was found to be a promising alternative to the TRUEX solvent for the actinide partitioning from simulated High Level Waste (HLW).