ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 11, pp. 1808!1815. + Pleiades Publishing, Inc., 2006.
Original Russian Text + M.Yu. Alyapyshev, V.A. Babain, N.G. Antonov, I.V. Smirnov, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79,
No. 11, pp. 1827!1835.
AND ION-EXCHANGE PROCESSES
Extraction of Americium and Europium
from Perchloric Acid Solutions with N, N<-Dialkyl-
and N, N, N<, N<-Tetraalkylpyridine-2,6-dicarboxamides
M. Yu. Alyapyshev, V. A. Babain, N. G. Antonov, and I. V. Smirnov
Khlopin Radium Institute, Research and Production Association, Federal State Unitary Enterprise,
St. Petersburg, Russia
Received September 15, 2006
Abstract-Extraction of americium and europium from perchloric acid solutions with pyridine-2,6-dicarbox-
amides was studied. The solvate numbers and Am/Eu separation factors were determined.
Dicarboxylic acid diamides are actively studied as
agents potentially suitable for the extraction of acti-
nides (especially minor actinides) from high-level
waste. Diamides of malonic , succinic, glutaric ,
diglycolic , dipicolinic , thiadiglycolic, and
some other acids [10, 11] were tested. Diglycolic acid
diamides appeared to be the best extractants of minor
actinides from acid solutions . Extraction properties
of picolinamides and dipicolinic acid diamides (pyri-
dine-2,6-dicarboxamides, PDAs) were studied .
N, N, N`, N`-Tetraalkyl-PDAs were shown to extract
americium only slightly. The extraction ability of
N, N, N`, N`-tetrahexylpyridine-2,6-dicarboxamide and
N, N, N`, N`-tetra(2-ethylhexyl)pyridine-2,6-dicarbox-
amide toward U(VI), Th(IV), and Fe(III) was also
studied by Mowafy et al. . Shimada et al. 
showed that a solution of N, N`-dimethyl-N, N`-di-
phenyl-PDA in CHCl
noticeably extracted rare-earth
elements from solutions with HNO
exceeding 3 M. N, N`-Dialkyl-N, N`-diaryl-PDAs in
fluorinated polar diluents efficiently extract Am from
nitric acid solutions . In this system, Am is ex-
tracted appreciably better than Eu; the Am/Eu separa-
tion factor in 132 M HNO
PDAs exhibit appreciable synergistic effect in
combination with chlorinated cobalt dicarbollide, pro-
viding efficient extraction of actinides and rare-earth
elements from acid solutions [12, 13].
It is known that metals are extracted with bidentate
neutral organophosphorus compounds (carbamoyl-
methylphosphine oxides, carbamoylmethylphospho-
nates, diphosphine dioxides) from perchloric acid
solutions considerably more efficiently than from
nitric acid solutions (so-called perchlorate effect).
In particular, for Am the difference reaches several
orders of magnitude . The perchlorate effect was
also revealed in the extraction of Am and Eu with
N, N`-dialkyl-N, N`-diaryl-PDAs .
We showed previously  that N, N`-dialkyl-N, N`-
diarylpyridine-2,6-dicarboxamides considerably sur-
pass the related dialkyl and tetraalkyl derivatives in
the extraction ability. Since Am and Eu are extracted
form perchloric acid solutions consdierably more
strongly, it was interesting to check whether the per-
chlorate effect would be observed with N-alkyl-sub-
Here we report on the extraction of Am and Eu
from perchloric acid solutions with N-alkyl-substi-
tuted pyridine-2,6-dicarboxamides in polar diluents.
Pyridine-2,6-dicarboxamides were prepared simi-
larly to . The formulas and NMR spectra of the
diamides are given below.