Chemistry Reference
In-Depth Information
100
Am
Nd
10
1
0.1
0.01
0
5
10
15
Dose (kGy)
FIGURe 8.13
Influence of the dose on the extraction of Am(III) and Eu(III) by 0.005 M
C5-BTBP in cyclohexanone. Irradiation of 0.005 M C5BTBP in cyclohexanone with a
60
Co
source (dose rate to water 40 Gy h
−1
). Extraction: equal volumes of irradiated organic and
aqueous phase (0.01M HNO
3
-0.99 M NaNO
3
spiked with
241
Am and
152
Eu) at room tempera-
ture (20°C). (Redrawn from Nilsson, M., Anderson, S., Drouet, F., Ekberg, C., Foreman, M.,
Hudson, M., Liljenzin, J.O., Magnusson, D., Skarnemark, G.
Solvent Extr. Ion Exch.
24:
299-318, 2006. With permission.)
However, variable effects on
D
Am
were observed with BTBPs, depending on the
ligand and the diluent (cyclohexanone or hexanol), namely an increase to almost
a factor of 2 or a decrease to a factor of 3-4 have been reported after 20 kGy for
CyMe
4
-BTBP and C5-BTBP, respectively (
237, 242
). The radiolytic stability of BTPs
and BTBPs seemed favored by an increase in their initial concentration (
240
).
8.3.4.2.1 Influence of the Extractant Structure
To avoid chemical attack on the α-benzylic hydrogens and thus improve the stability
of such polyazines, ligands with annulated rings were studied (see CyMe
4
-BTP or
BzCyMe
4
-BTP in Table 8.1). Based on extraction tests, the following stability scale
has been proposed:
n-
alkyl-BTP <
i
Pr-BTP ≤ CyMe
4
-BTP < BzCyMe
4
-BTP (
240,
243
). Molecules bearing branched alkyl groups, such as
i
Pr-BTP and CyMe
4
-BTP,
appeared to be less hydrolyzed than related linear alkyl compounds (i.e.,
n
PrBTP or
n
BuBTP) (
66, 244
), but the improved radiolytic stability of CyMe
4
-BTP was still
too unsatisfactory to be used in a process (
240
). The incorporation of an annulated
aromatic π-system added significant extra resistance to radiolysis (
243
).
In the BTBP family, the same tendency has been observed: the annulated CyMe
4
-
BTBP was more resistant to nitric hydrolysis than the alkylated compound C5-BTBP
