Chemistry Reference
In-Depth Information
was reduced (lower than 0.03 mol L
−1
). Other experiments performed with 0.2 mol L
−1
TODGA (with and without 0.5 mol L
−1
TBP) in TPH, in contact with 3.0 mol L
−1
nitric
acid showed only a slight decrease in
D
Am
above 0.6 MGy and no significant influ-
ence on
D
Eu
(
227
). On the other hand, at low acidity, the values of
D
Am
increased after
irradiation of the solvent (as presented in Figure 8.12), which could lead to potential
difficulties in the splitting step with dilute nitric acid. Specific investigations into the
behavior of
N,N
-dioctyl-3-oxapentan-1,5-amide acid (Figure 8.10a) allowed it to be
established that this compound played a noticeable role at low acidity, as do classical
acidic extractants, and had a synergistic effect on the extraction at high acidity.
D
Am
increases from 24 to 80 in the presence of 0.02 mol L
−1
of the amide acid (
229
).
8.3.3.3.4 Influence of the Extractant Structure
The protective effect of aromatic diluents has encouraged authors to test the radio-
lytic stability of TODGA derivatives possessing an aromatic moiety. Two molecules
were synthesized:
N,N,N
´
N
´-tetra(
p
-octylphenyl)diglycolamide (T(OPh)DGA) and
N,N,N
´
,N
´-tetra-octylfuran-2,5-diamide (TOFDA) (
183
). The order of radiolytic
stability was T(OPh)DGA > TOFDA > TODGA, which indicates that the presence
1000
100
10
1
0.1
0.01
0.01
0.1
1
10
[HNO
3
]
aq
(mol/L)
FIGURe 8.12
Influence of irradiation on extraction of Am(III) from HNO
3
by 0.1 M
TODGA in
n
-dodecane before (o) and after 422 kGy (
®
). Gamma irradiation of 0.1 M
TODGA in
n
-dodecane pre-equilibrated with HNO
3
with
60
Co source—4.8 kGy h
−1
dose
rate—in air at room temperature. Extraction: equal volume of organic and aqueous phase
(HNO
3
spiked with tracer -1.0 × 10
16
Bq). Temperature: 25 ± 0.1°C. (Redrawn from Sugo,
Y., Sasaki, Y., Kimura, T., Sekine, T., Kudo, H.
Proceeding of the International Conference
Global 2005
, Tsukuba, Japan, 9-13 October, Paper No. 368, 2005.)
