EXTRACTION OF NP(IV), NP(VI), PU(IV) AND U(VI) WITH AMIDES, BEHSO ANDCMPO FROM NITRIC-ACID MEDIUM

The extraction of Np(IV), Np(VI), Pu(TV) and U(VI) from a nitric acid medium has been carried out with dibutyldecanamide (DBDA), dihexyldeca namide (DHDA), bis-2-ethylhexylsulphoxide (BEHSO) and yl(phenyl)-N-N-d iisobutyl-carbamoylmethylphosphine oxide (CMPO) using n-dodecane as th e diluent. The order of extraction for the metal ions is CMPO>BEHSO>DH DA>DBDA. The species extracted into the organic phase was found to be the disolvate with all the extractants while using hexavalent metal io ns Np(VI) and U(VI) and also with tetravalent ions Np(IV) and Pu(IV) i n the case of BEHSO and CMPO. However, in the case of DBDA and DHDA, N p(IV) and Pu(IV) were extracted as the trisolvate species. The equilib rium constant (K) for the formation of the above species has been eval uated after applying the possible correction factors. In general, logK increases with increasing basicity of the extractants. In the case of amides, the plot of logK verses k(H) (acid uptake equilibrium constan t) gave straight lines which could be represented by the empirical equ ation: logK(U(VI)) = 5.17 kH + 0.18 and logK(Pu(IV)) = 3.11 kH + 1.81 for the respective metal ions. With the help of these empirical equati ons it is possible to predict the equilibrium constant values of amide complexes of U(VI) or Pu(IV) if the k(H) values of amides are known. The solid complexes of U(VI) with DHDA and CMPO were synthesized and c haracterized by elemental analysis and IR spectra. Two molecules of DH DA and only one molecule of CMPO are bound with U(VI). The bidentate n ature of CMPO in its solid species has been confirmed.