INORGANIC SYNTHESIS AND INDUSTRIAL
ISSN 1070-4272, Russian Journal of Applied Chemistry, 2014, Vol. 87, No. 8, pp. 1038−1043. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © E.P. Lokshin, O.A. Tareeva, I.R. Elizarova, 2014, published in Zhurnal Prikladnoi Khimii, 2014, Vol. 87, No. 8, pp. 1053−1058.
Sorption Conversion of Phosphate Concentrates
of Rare-Earth Metals
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, Akademgorodok 26a, Apatity, Murmansk oblast, 184209 Russia
Received July 17, 2014
Abstract—Treatment of phosphate concentrates of rare-earth elements with low-concentration nitric acid in the
presence of a sulfocation exchanger (sorption conversion) enables effective separation of rare-earth elements
from phosphorus and ﬂ uorine. The effect of the nitric acid concentration and temperature on the efﬁ ciency of the
sorption conversion of rare-earth element phosphates and the behavior of cationic impurities in the course of the
sorption conversion were studied. It was shown that no selective transfer of thorium into solution could be achieved
in the course of conversion and subsequent desorption with solutions containing nitric acid or ammonium nitrate.
In neutralization of the nitric-phosphoric acid solution,
an intermediate product of the nitric acid processing of the
Khibiny apatite concentrate, rare-earth elements (REEs)
can be isolated in the form of a phosphate concentrate .
Recently, a more effective way to obtain a concentrate of
this kind has been developed, which made it possible to
substantially raise the yield and concentration of REEs
in the concentrate . In this method, the concentrate is
formed at elevated temperatures (85–95°C). A signiﬁ cant
part of thorium and uranium contained in apatite is trans-
ferred into the REE concentrate.
A number of approaches have been suggested for sepa-
rating phosphorus from REE phosphates. These include
the extractive recovery of phosphoric acid from solutions
produced by dissolution of the phosphate concentrate in
mineral acids (commonly nitric acid), conversion of REE
phosphates to oxalates, carbothermic removal of phos-
phorus, etc. These methods can remove phosphorus, but
each has certain shortcomings. Therefore, development
of a more perfect method for processing of the phosphate
REE concentrate is a topical task.
In the ﬂ uorophosphate REE concentrate produced
from the extraction phosphoric acid by the dihydrate
process , phosphorus, ﬂ uorine, and a substantial part of
impurity cations were separated from REEs by the sorption
conversion method via interaction of the concentrate with
a sulfocation exchanger in a sulfuric acid medium . In
the process, REEs and a certain part of cationic impuri-
ties were transferred to the sorbent, with phosphorus and
ﬂ uorine remaining in the sulfuric acid solution. REEs can
be recovered from the sulfocation exchanger by the known
methods [5, 6], and the sulfuric acid solution containing
phosphorus and ﬂ uorine can be recycled to processing of
the apatite concentrate. In the course of processing of the
REE-containing sulfocation exchanger, radio nuclides,
mostly thorium, are effectively separated and concentrated
in a product with increased radioactivity.
The REE concentrates produced from nitric-phos-
phoric acid solutions contain a substantial amount of
calcium, which will form difﬁ cultly soluble gypsum in a
sulfuric acid treatment. REEs isomorphously crystallize
with gypsum, which leads to their signiﬁ cant loss in the
conversion process. In addition, the utilization of the sul-
furic acid solutions formed in the nitric acid processing
of apatite is difﬁ cult.
It was of interest to study the fundamental aspects of
the sorption conversion of the phosphate REE concentrate
in nitric acid media.