Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 5, pp. 773−781.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © E.P. Lokshin, O.A. Tareeva, I.R. Elizarova, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 5, pp. 743−751.
INORGANIC SYNTHESIS AND INDUSTRIAL
Deposition of Rare Earth Elements from a Wet-Process
Phosphoric Acid by Fluorine Compounds
E. P. Lokshin, O. A. Tareeva, and I. R. Elizarova
Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials,
Kola Scientiﬁ c Center, Russian Academy of Sciences, Apatity, Russia
Received May 4, 2010
Abstract—Effect of type and consumption of ﬂ uorine reagents (HF, NH
F and NaF) on the deposition
of rare earth elements from the wet-process phosphoric acid of the dihydrate process was examined.
Wet-process phosphoric acid (WPPA) being pro-
duced in processing Khibiny apatite concentrate by sul-
furic acid dehydrate technique contains 36–38 wt % of
and 0.1–0.12 wt % (in terms of oxide) of a sum
of rare earth elements (REEs) (ΣLn
) enriched in
comparison with REE sum of the apatite concentrate by
yttrium and lanthanides of middle and yttrium series [1,
2]. An amount of admixtures in WPPA of various manu-
factures is as a rule in a range (g l
): СаО 3.7–10.0,
15–30, F 17.5–21,
10–15 . A range in the admixture amount is due
to variability of a mineral composition of apatite con-
centrate and to features of technology on various manu-
factures. In production conditions the WPPA of dihy-
drate process is 70–80°C and use of WPPA cooling in
REE recovery is unacceptable.
In  it was demonstrated expediency of developing
the techniques on recovery of REE from WPPA
obtained by sulfur acid dihydrate process from Khibiny
apatite concentrate and an analysis of earlier developed
solutions of this problem.
In introduction in WPPA of sulfur acid and sodium
compounds with 81.6–87.7 recovery REE concentrates
are precipitated which contain 10.5–19.5 wt % of
REE sum and represent a blend of double sulfates of
lanthanides with sodium, calcium sulfate dihydrate and
sodium hexaﬂ uorosilicate . However, this approach
is invalid for extraction of REE compounds from
a production WPPA since it requires the creation of 10–
15 wt % concentration of sulfur acid in WPPA.
Compositions of complexes being formed by
impurities in WPPA are unknown. It is believed that in
non-evaporated phosphoric acid of hemihydrate process,
containing about 36 wt % of P
(48.7 wt % H
aluminum and iron present in the form of dissolved
complex compounds AlF
(OH), where M = Fe
In addition it is alleged that compounds МF
, where М = Al
, are sorbed by
activated carbon from WPPA of hemihydrate process
Wet-process phosphoric acid contains signiﬁ cant
amount of ﬂ uorine compounds that, however, does not
lead to precipitation of REE ﬂ uorides. In introduction
in it of compounds containing sodium cation Na
can be deposited with high recovery (about 90%) from
WPPA. This points to predominance of silicon(IV)
ﬂ uoride complex in WPPA.
The goal of this examination was studying possibility
of precipitation of REE ﬂ uorides from WPPA.
Simultaneously we assessed an effect of introduction
of ﬂ uoride anion on deposition of other impurities.
We accounted for that an excessive amount of ﬂ uoride
further can be removed in evaporation of WPPA [5, 6]
In the study we used WPPA of a manufacture