Malonamides DIAMEX process

Berthon, L., Morel, J.M., Zorz, N. et al. 2001. DIAMEX process for minor actinide partitioning Hydrolytic and radiolytic degradations of malonamide extractants. Sep. Sci. Technol. 36 (5 6) 709-728. 

Bidentate oxygen-donor extractants include the neutral diamide compounds, such as the malonamides used in the French DIAMEX and DIAMEX-SANEX processes, RR N(C=0)-CHR"-(C=0)NRR the bisphosphine oxides, RR (P=0)- CIIR"-(P=0) RR the carbamoyl-(methyl)-phosphinates, R0R 0(P=0)-(CI I On o 0rr(C=0)NRR or the more efficient carbamoyl-methyl-phosphine oxides, RR (P=0)-CHR"-(C=0)... 

Di(2-ethylhexyl) phosphoric acid (HDEHP) is an extractant molecule used for An(III)/Ln(III) separation. Used in TALSPEAK-type processes in a mixture with TBP, or in the DIAMEX-SANEX process in a mixture with a malonamide (154-157), it has also been proposed, in a mixture with TBP, to remove strontium from PUREX acid waste solution in the Hanford B plant (158). Therefore, numerous studies have focussed on the radiolytic degradation of HDEHP and its effects on the extraction of Sr(II), lanthanides(III), and actinides(III) (10, 158-163). 

In the context of the DIAMEX-SANEX process development, the stability of the solvent (a mixture of malonamide and HDEHP extractants in alkane) was studied in the MARCEL loop (y-irradiation followed by alkali treatments). No accumulation of HDEHP degradation products was observed, and most of the physical and chemical properties of the solvent were maintained (5). 

In the DIAMEX-SANEX process, the presence of malonamide protected HDEHP (5, 10, 32) but it should be noted that the presence of dialkyl phosphoric acid in the organic phase had a slightly negative effect on the malonamide s stability (5, 48, 71) ... 

The DIAMEX (DIAMide Extraction) process was first developed by Musikas (1987) at the Fontenay-airx-Roses Research Center (France) and by Madic and Hudson (1998) to extract minor actinides (americium and curium) and lanthanides to reduce the radiotoxicity and volume of waste. This process is based on the use of malonamide extractants (Figure 1427). For the first version of DIAMEX, di-methyl-di-butyltetradecylmalonamide (DMDBTDMA) was developed (Madic et al., 2002 Musikas, 2006 OECD, 1999,124-125), including countercurrent... 

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