THE RADIOCHEMISTRY OF PLUTONIUM - Sciencemadness.org

the TBP cone entration. Solovkin 391 has calculated distribution coefficients for this
system on a semi-empirical basis and obtained good agreement with experimental data.
Tetra- and hexavalent Pu as well as other actinides have been shown to be di-
solvates in the organic phase. 44 The extracted complexes are then PU(N03)4 r 2 TBP
for Pu(IV) and PU02(N03)2 . 2 TBP for Pu(VI). Work with trivalent Pu has shown that
the extracted complex is tri-solvated, Pu(N03)3 3 TBP. 372 Laxminarayanan et al. 252
have shown that Pu(IV) in 2-4 ~ HTT03 is associated with an average of 2.6 nitrate ions
and does not exist as undissociated Pu(N03)4 by combining solvent extraction data
from several solvents. There is direct evidence that the complexes are un-ionized in
the organic phase. 170
Typical data for the extraction of a number of elements at trace concentration
into 19 volume ~. TBP ‘in kerosene from nitric acid solution of various concentrations
are shown in Fig. 1. The distribution coefficients rises steeply at low nitric acid
concentrations because of the strong salting-out effect of the nitrate ion (Eq. 1),
passes through a maximum, and then falls at higher acid concentrations. Some
elements (e. g. Th and Y) pass through minima and rise again.
,o-’o&u+dLu+
I I I
I Zr I
E(XJl LlBRi8M
HN03 CONCENTRATION, AQUEOUSJM)
Fig. 1, Extraction of mtrates at trace
concentration mt~ 19 volume ~0 TBP in
kerosene at 25oC from nitric aci 258 solutions
Taken from McKay and Healy. The in- -
dividual reference’s are: ~trium350;
thorium 179. zirconium2 , uranium and
neptunium2d: and plutonium44~ 258.
30
Several other studies of the ex-
traction of Pu from nitric acid solutions
have been reported. Carleson
76
used
40~. TBP in kerosene and paid partic-
ular attention to requirements to main-
tain Pu in the desired oxidation state.
He found that NaN03 was necessary to
prepare pure Pu(IY) from an equilibrium
disproportionated mixture. Figure 2
shows the effect of HN03 concentration
on several reducing agents in the ex-
traction of an equilibrium Pu solution,
and the extraction curve for Pu(llI)
alone. Ferrous sulfamate with added
hydroxylamine effects complete re-
duction of Pu(IV ) to Pu(IH) at up to 2 ~
HN03, but fails at higher acidities.
Ferrous ion plus hydrazine and hydrox-
ylamine fail to complete the reduction
at progressively lower acidities.
Carleson also found that solid KBr03
did not oxidize Pu(IV) to Pu(VI) in 1.55
~ HN03 at room temperature, but that
the oxidation was quantitative in 0.1 ~
Br03- after heating to 95°C for several
hours.
Codding et al. 92, 93 used 307.
TBP in kerosene, Rozen and Moiseenko
334