Malonamides DIAMEX-SANEX process

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) ... 

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