THE RADIOCHEMISTRY OF PLUTONIUM - Sciencemadness.org

metal atom at high nitrate concentrations. Zr exhibits a maximum distribution co-
efficient at about 7 M HN03 and decreases at higher acidities. A large decrease in the
—
distribution coefficient of quadrivalent Pu and Th occurs as the branching of the alpha
carbon atom is increased. while that of U(VI) is only decreased moderately. N, N-
dihexyloctanamide was superior to TBP in decontamination of Pu from Zr-Nb, but
slightly inferior for Ru decontamination. The potential uses of these compounds are
(1) as selective extractants for quadrivalent actinides, or (2) as selective extractants
for U(VI) in the case of amides with highly branced alpha carbon atoms (e. g. N, N-
dihexyltrialkylacetamide).
Chelating Agents
A large number of hi-functional reagents which form strong coordination
complexes with metal ions have been investigated. These complexes are more soluble
in non-polar organic solvents such as benzene or carbon tetrachloride than in the
aqueous phase, and are therefore extractable. Of these compounds the fluorinated
HN03 CONCENTRATION AT
EQUILIBRIUM (~)
Fig. 34. Extraction of actinides
and Zr by 1.09 ~ N, N-dibutyloctanamide
in n-dodecane at 30°.378
13-diketone, 2-thenoyltrifluoro acetone (TTA ) and
the ammonium salt of N-nitrosophenylhydroxyl-
‘amine ( “Cupferron” ) have been used most widely
in radiochemical and analytical applications.
formula
Thenoyltrifluoro acetone (TTA)
u
s
This compound has the structural
_~_cH _~_cF
2 3
and exists primarily in the enol form in both
aqueous and organic solutions,
TTA forms strong complexes with many
metal ions, particularly those of high valence.
The general reaction for the extraction can be
written as
M +m
+ m ‘T(o) = ‘Tin(o) + ‘H+
and the equilibrium constant
(MT)(0) (H+)m
K= (2)
(M+m) (H%o)
where the quantities in parentheses are activ-
ities.
Thus, if activity coefficients, are neglected,
and no aqueous completing occurs, the distribu-
tion coefficient should show a direct ~th power
65
(1)