Extraction of Lanthanide(III) and Uranyl(VI) from Nitric Acid Solution by Malonamides
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EXTRACTION OF LANTHANIDE(III) AND URANYL(VI) NITRIC ACID SOLUTION BY MALONAMIDES
FROM
Takashi NAKAMURA, Yuki MATSUDA and Chie MIYAKE Department of Nuclear Engineering, Faculty of Engineering, Osaka university, Yamadaoka, Suita-shi, Osaka 565, Japan
ABSTRACT The extractive properties of two malonamide extractants, DMDBO 3 NPDA and DMDBMA were investigated for the extraction of lanthanide(III) and uranyl(VI) ions in benzene-nitric acid systems. It was found that DMDBO 3 NPDA has a higher extractive capacity than DMDBMA. The difference in their extracting capacities is discussed, based on the enthalpy changes for the extraction reactions and IR data for complexes of metal nitrates with malonamides. In addition, the applicability of a mixed solvent of n-dodecane and some aliphatic alcohols as a diluent for DMDBO 3 NPDA was examined. The longer the carbon chain and the higher the concentration of the aliphatic alcohol, the more the phase compatibility improves. The distribution ratios of neodymium(III) ion increase with an increase in the carbon chain length of linear aliphatic alcohol and with a decrease in its concentration. INTRODUCTION The malonamide ( diamide ) compounds have been given much attention in recent years as a new extractant for generic TRU elements[1,2]. In particular, N,N'-tetraalkylmalonamide and its derivatives( pentaalkylmalonamides ) are known to have good extracting capacity for americium(UII) ion in nitric acid solution. Recently, the DIAMEX ( DIAmide EXtraction ) process using pentaalkylmalonamide as an extractant has been proposed for reprocessing in the near future[3,4]. The advantage of diamide extractants is that they are more amenable to incineration as a solvent waste. In addition, the ease of their syntheses relative to other organophosphorus extractants and the relatively weak influence of degradation products on their extracting capacity are favorable for reprocessing. However, for the DIAMEX process, the optimization of the extractant formula and the diluent has not been completely achieved[5]. In addition, data on the extracting capacity and the scaleup of the technology are insufficient at present.
0 CH3-NC C
0 .\ NCH3
GH
CH
/N NN
A
C4 H9
(C 2H4
0
BB B
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6H13C Fig.
1
3
QC 4 H9
Structure of Malonamide Extractants ( A: DMDBO 3 NPDA, B: DMDBMA )
Mat. Res. Soc. Symp. Proc. Vol. 353 0 1995 Materials Research Society
4 H9
1294
Our work was undertaken to investigate extractive properties of N,N'dimethyl-N,N'-dibutyl-2-(3-oxanonyl)-propane-1,3-diamide( DMDBO 3 NPDA : Fig. 1A) for lanthanide(Ifl) and uranyl(VI) ions in benzene-nitric acid systems and then to compare them with those of N,N'-dimethyl-N,N'-dibutylmalonamide ( DMDBMA : Fig. 1B ). Moreover, to gain insight into the selection of adequate extraction solvent for the DIAMEX process, the applicability of some aliphatic alcohol /n-dodecane mixtures to the diluent for DMBDO 3 NPDA was examined. EXPERIMENTAL N,N'-dimethyl-N,N'-dibutylmalonamide according
to
the
literature[e].
(
DMDBMA
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