ISSN 1070-4272, Russian Journal of Applied Chemistry, 2015, Vol. 88, No. 9, pp. 1551−1554. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © E.P. Lokshin, O.A. Tareeva, 2015, published in Zhurnal Prikladnoi Khimii, 2015, Vol. 88, No. 9, pp. 1364−1368.
Reaction of Aluminum, Iron(III), and Titanyl Cations
Anions in Sulfuric and Nitric Acid Solutions
E. P. Lokshin and O. A. Tareeva
Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials,
Kola Science Center, Russian Academy of Sciences, Akademgorodok 26a, Apatity, 184209 Russia
Received October 1, 2015
Abstract—The ﬂ uorine distribution between SiF
anions and aluminum, iron(III), and titanyl cations in sulfuric
and nitric acid solutions containing phosphate ion depends on the kind of ﬂ uoride acceptor cation, solution acidity,
composition of the acid solution, and reaction time. The data obtained allowed the development of an efﬁ cient
technology for preparing nonradioactive rare earth concentrates by sulfuric acid leaching of phosphogypsum.
As shown previously , sulfuric acid leaching
of rare earth elements (REE) from phosphogypsum
is accompanied by transfer of thorium into solutions.
Although its concentration in solutions is low, it is
sufﬁ cient for the rare earth concentrates recovered from
them to be radioactive. Large amounts of thorium are
also present in the ﬂ uoride–phosphate REE concentrate
precipitated from wet-process phosphoric acid from the
dihydrate process by adding ammonium ﬂ uoride, and
also in the phosphate REE concentrate recovered in the
course of neutralization of solutions from nitric acid
breakdown of apatite concentrate. It is recommended
that these concentrates be processed by methods of
sorption conversion performed in the slurry containing
low concentrations of sulfuric or nitric acid. In sorption
conversion, a signiﬁ cant fraction of thorium is taken
up by the sorbent without separation from REE. It is
interesting to perform separation of RRE and thorium in
Thorium can be bound in poorly soluble ﬂ uoride
by adding into solution compounds containing
ﬂ uoride ion, e.g., ammonium or alkali metal ﬂ uorides.
However, although the ThF
solubility is very low, the
ﬂ uoride ion introduced into a low-concentration sulfuric
acid solution primarily forms soluble ﬂ uoride complexes
with aluminum, rather than insoluble thorium ﬂ uoride.
This fact complicates determination of the amount of the
ﬂ uoride-containing compound that should be introduced
into the solution to precipitate thorium ﬂ uoride . On
the other hand, introduction of ﬂ uoride ions in a large
excess leads to the precipitation of REE ﬂ uorides, which
are limitedly soluble in low-concentration sulfuric acid
solutions. Similar pattern is observed in low-concentration
nitric acid solutions.
The solutions also contain iron(III) and titanyl cations,
which can also form ﬂ uoride complexes in acid solutions.
Information on the relative stability of the above
ﬂ uoride complexes in sulfuric and nitric acid solutions,
including solutions containing phosphate anions, is
virtually lacking, although these data are necessary for
the development of methods for reducing the thorium
transfer into solution in the course of REE leaching
from phosphogypsums, and also for the development of
a process for sorption conversion of phosphate–ﬂ uoride
REE concentrates, which can be precipitated from wet-
process phosphoric acid or from the nitric acid extract
from processing of apatite concentrate on cooling this
extract to low temperatures.
Therefore, it is topical to study the interaction of
aluminum, iron(III), and titanyl cations with SiF
in sulfuric and nitric acid solutions.