1070-4272/04/7704-0555 C 2004 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 77, No. 4, 2004, pp. 555!558. Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 4, 2004,
Original Russian Text Copyright + 2004 by Pyartman, Kudrova, Keskinov.
OF SYSTEMS AND PROCESSES
Phase Separation in the Systems Constituted by
Tetradecane (Hexane, Decane), Tri-n-Butyl Phosphate, and
Cerium(III) Nitrate Solvate with Tri-n-Butyl Phosphate
A. K. Pyartman, A. V. Kudrova, and V. A. Keskinov
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received April 16, 2003
Abstract-Phase diagrams of ternary liquid systems constituted by tetadecane (hexane, decane), tri-n-butyl
phophate, and cerium(III) nitrate solvate with tri-n-butyl phosphate Ce(NO
with phase separation
into liquid phases I and II were studied at 298.15 K. Phase I is enriched in the hydrocarbon diluent, and
phase II, in Ce(NO
. The distribution of components between phases I and II was considered.
Extraction of rare-earth elements (REE) with neu-
tral organophosphorus compounds, e.g., tri-n-butyl
phosphate (TBP) in hydrocarbon diluents (HCDs), is
widely used in their recovery and separation. The con-
centration and type of a diluent affect the extraction
isotherms and element separation factors . At a low
TBP content in HCD, phase separation of the organic
phase into two phases is possible. This effect has been
studied in detail for actinides . At the same time,
phase diagrams of ternary liquid systems constituted
by tetadecane (hexane, decane), TBP, and lanthani-
de(III) nitrate solvate with TBP in the region of phase
separation are unknown, although such diagrams can
be of practical interest in the choice of HCD and com-
ponent concentrations for extraction systems.
Vacuum-distilled TBP (density r = 0.9727 g cm
at 298.15 K) and tetradecane (0.7592 g cm
(0.7263 g cm
), and hexane (0.6548 g cm
) of chem-
ically pure grade were used. Cerium(III) nitrate sol-
(S), was prepared by threefold
saturation of TBP with fresh portions of a saturated
aqueous solution of cerium(III) nitrate . The [con-
centration] of Ce(NO
in pure S was 1.12 M
(r = 1.2755 g cm
). The S concentration in the or-
ganic phase was determined complexometrically .
The phase densities were determined pycnometrically.
The binodal curves of the ternary systems were meas-
ured by Alekseev’s method  by titration of binary
systems with different compositions with the third
component under the temperature control.
Mixtures of tetradecane (hexane, decane) and S
taken in various volume ratios (2.5310 cm
geneous systems) were titrated with TBP, using a mi-
croburet, until the system became homogeneous. In
parallel experiments, mixtures of TBP and S (homo-
geneous systems) were titrated with the diluent until
the second organic phase formed.
The formation of the second organic phase was ad-
ditionally monitored by nephelometry with a Kernco
966 R turbidimeter equipped with a color filter (l =
850 nm). To determine the nodes (compositions of the
coexisting phases), the phase volumes were measured
(in special experiments, we showed that, within the
error of +0.2%, the system volume is equal to the sum
of the component volumes). With regard to binodals
and solution densities, the concentrations of TBP and
diluent were determined from the S concentration .
In this case, a binodal was plotted using volume frac-
tions under the condition that the total volume re-
mains unchanged when the components are mixed.
Later on, the phase composition was recalculated to
weight fractions to obtain the phase density.
Additionally, the TBP content was determined as
the difference between the total TBP concentration
and TBP concentration in S, evaluated after cerium
stripping into water, the subsequent saturation of
the organic phase with cerium(III) nitrate, and deter-
mination of the S concentration. The TBP concentra-
tion was determined from the phosphorus content
measured with an SF-26 spectrophotometer in 1-cm