ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 2, pp. 196!200. + Pleiades Publishing, Inc., 2006.
Original Russian Text + V. M. Lembrikov, V. V. Volkova, G. P. Zhavoronkova, L. V. Konyakhina, 2006, published in Zhurnal Prikladnoi Khimii, 2006,
Vol. 79, No. 2, pp. 198!202.
OF SYSTEMS AND PROCESSES
Properties of the Extraction System Constituted
by Phosphoric Acid Produced from Khibiny Apatite
and Tri-n-Butyl Phosphate
V. M. Lembrikov, V. V. Volkova, G. P. Zhavoronkova, and L. V. Konyakhina
Voskresenskii NIUiF (Voskresensk Research Institute of Fertilizers and Phosphoric Acid)
Open Joint-Stock Company, Voskresensk, Moscow oblast, Russia
Received June 22, 2005
Abstract-Data on the equilibrium distribution of phosphoric acid among the aqueous and organic phases
in extraction of phosphoric acid with tri-n-butyl phosphate are presented for the system constituted by phos-
phoric acid produced from the Khibiny concentrate and by the extracting agent from the industrial system
for purification of extraction phosphoric acid at 25350oC.
Liquid extraction with organic solvents is a promis-
ing method for purification of substances and, in par-
ticular, that to remove impurities from the extraction
phosphoric acid (EPhA). Liquid extraction is used on
the industrial scale to purify the apatite EPhA with tri-
n-butyl phosphate (TBP) as extracting agent .
The properties of the following systems have been
described in the literature: H
O3TBP at 25oC
 and 2933343 K , and H
at 2933353 K ; the systems were composed of
reagent phosphoric acid of pure grade and TBP of
The present study is concerned with the distribu-
tion of phosphoric acid among the organic and aque-
ous phases of composition close to that in industrial
manufacture of purified phosphoric acid. The exper-
iments were performed at 25350oC and 2553764 g l
phosphoric acid in the aqueous phase (in terms of
). The choice of the given range of temperatures
and concentrations was governed by the real condi-
tions of industrial purification of EPhA. The solutions
were prepared by saturating an extracting agent from
the industrial system with extraction phosphoric acid.
In the concentration of impurities in the aqueous and
organic phases, this system corresponds to that in
the stage of EPhA extraction in manufacture of puri-
fied phosphoric acid.
An evaporated desulfated EPhA produced from
the Khibiny apatite concentrate was used in the ex-
periments. The acid had a density of 1.537 g cm
the following composition (wt %): P
0.262, and Fe
0.21. The extracting agent
from the technological system was used for extraction.
The temperature in the experiments was maintained
constant by thermostating to within +0.5oC. The con-
tent of phosphoric acid in the organic phase was de-
termined by potentiometry . The results of the ex-
periments are presented in Table 1 and Fig. 1.
A mathematical processing of the experimental
data demonstrated that the equilibrium contents of
in the organic and aqueous phases are related
by an extraction equation similar to the Hand equa-
is the content of P
in the or-
ganic phase (g l
, that in the aqueous
phase (g l
); and a and b, coefficients of the equation.
It should be noted that the re-extraction of phos-
phoric acid from the extracting agent with water was
calculated using the data reported in , where equa-
tions describing the process were also presented.
However, two equations for two different tempera-
ture ranges were reported. Therefore, a similar pro-