1070-4272/02/7502-0191 $27.00 C 2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 2, 2002, pp. 191!194. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 2, 2002,
Original Russian Text Copyright C 2002 by Dibrov, Chirkst, Litvinova.
AND ION-EXCHANGE PROCESSES
Thermodynamic Analysis of Cerium(III) Extraction
from Sulfate Solutions with Salts of Quaternary
I. A. Dibrov, D. E. Chirkst, and T. E. Litvinova
Plekhanov State Mining Institute, St. Petersburg, Russia
Received August 31, 2000; in final form, April 2001
Abstract-Cerium(III) distribution between an aqueous sulfate solution and a solution of trialkylbenzylam-
monium sulfate in xylene was studied. The Ce(III) distribution coefficient grows with increasing pH. The ex-
traction is provided by the formation of cerium mono- and disulfate complexes in the aqueous phase. Schemes
of extraction equilibria are proposed and Gibbs energies and equilibrium constants are found.
Russia has no domestic resources of purely rare-
earth ores, such as bastn1asite, monazite, and xenotime,
widely used in the rare-earth industry abroad. The rare-
earth metals (REMs) are produced as coproducts with
other less-common metals (niobium, uranium, etc.) in
smaller amounts than it is necessary for the industry.
Therefore, a search for new raw materials containing
REMs, development and improvement of flow-sheets
for their recovery and separation are topical tasks.
Extraction recovery of REM from sulfate media is ex-
pedient when poor ores, e.g., eudialyte ores of the Al-
luive bed  or by-products of the chemical and
metallurgical productions are processed. Published
data on extraction recovery of REM sulfates are
scarce. In particular, it is known that REM sulfates
are poorly extracted with neutral organophosphorus
compounds, e.g., tributyl phosphate (TBP) . Other
widely used extractants are salts of quaternary am-
monium bases [3, 4].
The main features of the cerium extraction were
studied in sulfuric acid (0.3734.37 mol kg
tions of cerium sulfate at pH 034 and constant con-
centration of sulfate ion, 2.55 mol kg
by adding a required amount of chemically pure
grade magnesium sulfate. This concentration of sul-
fate ion corresponds to that used in the experiments
on sulfuric acid leaching of eudialyte concentrate .
A 0.5 M solution of trialkylbenzylammonium sulfate
alkyl radicals (TABAS) in xylene was
used. The volume ratio of the organic and aqueous
phases was 1 : 2. The Ce(III) molality in the organic
was found as the difference of metal mol-
alities in the initial C
and equilibrium aqueous C
phases with regard to mass ratio of aqueous m
and organic m
= 2.4 under con-
ditions of the experiment):
The Ce(III) content in the aqueous phase was mo-
nitored spectrophotometrically with arsenazo III .
The experimental distribution coefficient D was
found by the formula
Phases were mixed with a magnetic stirrer and sep-
arated in a separatory funnel; the phase separation
time was 15320 min. Experiments were performed at
room temperature without thermostatic control, since
small variations of temperature (+5oC) do not affect
substantially the distribution coefficient .
It is accepted that the photometric measurements
are performed with 5% relative error at 95% con-
fidence probability. Therefore, the distribution coef-
ficients D were determined with +7% relative error.
The theoretical error of the calculated equilibrium
constants and Gibbs energies of extraction was not
determined because of the difficulty of its calcula-
tion. The arithmetic mean values of these parameters
were found, and the root-mean-square deviation from
the average with regard to Student’s coefficient was
taken as an error.