Chemistry Reference
In-Depth Information
tAbLe 4.25
Distribution Ratios for eu, np, Pu, and Am from Aqueous solutions 4 M
nano
3
, 1 M Hno
3
into a nPHe solution of Linear oligomers or Calixarenes
bearing the CMPo Moieties on the Wide Rim (10
−
3
M)
C
Ligand
152
eu
237
np
239
Pu
241
Am
0.85
22
1.2
OΦCMPO
10
−2
M
O
5
1
0.5
0.3
10
−3
M
<0.001
<0.001
O
5
2
1.2
0.9
23
1.8
10
−3
M
O
5
3
13
2
20
17
10
−3
M
CPw3
10
−3
M
>100
2
>100
>100
CPw4
2
20
45
10
−3
M
>100
CPw5
2
90
10
−3
M
>100
>100
CPw6
−
4
10
−3
M
>100
>100
CPw7
2
80
10
−3
M
>100
>100
CPw8
10
−4
M
1.1
27
27
CPw9
1.5
a
24
a
21
a
10
−4
M
CPw10
12
61
10
−3
M
>100
>100
CPw11
2
10
−3
M
>100
>100
>100
CPw12
3
10
−3
M
>100
>100
>100
CPw13
10
−3
M
>100
3
>100
>100
a
Precipitation of a part of actinides.
group (O
5
3) does not improve the extracting ability toward plutonium, but enhances
strongly that of americium, which needs three CMPO molecules to be extracted.
4.5.2.1.2 Extraction by Wide-Rim CMPO Calixarenes
Complexation studies of some lanthanides and thorium in methanol have been
undertaken in order to better understand the solution behavior of OΦCMPO and
CPw3.
160
The stability of the complexes increases along the lanthanides series as a
consequence of the increase in the charge density of the cations due to the lanthanide
contraction (Table 4.25).
The complexes with the two rigid derivatives CPw3 and CPw2 have similar
stabilities
(
log β
11
= 6.2), whereas the stability of the flexible tetramethoxy deriva-
tive CPw1 is much lower
(
log β
11
= 4.4). The stability increases with the number
of propoxy groups (from CPw14 to CPw16), that is, when the molecule becomes
increasingly rigid.
Extraction of thorium and europium by these same compounds shows an increase
from O
5
1 to O
5
5 (Table 4.26). Thorium is equally extracted by the linear tetramer
and pentamer, whereas europium is even better extracted by linear tetramer than by
the linear pentamer. Most of the CMPO calixarenes extract europium better than
TOPO and OΦCMPO. All these extractants are stronger extractants of thorium than
europium, because similar efficiencies require ligand concentrations of 10
−3
M for
