Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 1, pp. 6−11.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
V.S. Rimkevich, A.A. Pushkin, Yu.N. Malovitskii, L.P. Dem’yanova, I.V. Girenko, 2009, published in Zhurnal Prikladnoi Khimii, 2009,
Vol. 82, No. 1, pp. 8−13.
AND INDUSTRIAL INORGANIC CHEMISTRY
Fluoride Processing of Non-Bauxite Ores
V. S. Rimkevich, A. A. Pushkin, Yu. N. Malovitskii, L. P. Dem’yanova, and I. V. Girenko
Institute of Geology and Nature Management, Far Eastern Division, Russian Academy of Sciences,
Received February 22, 2008
Abstract—Integrated processing of non-bauxite ores using ammonium hydrogen difluoride was studied.
The kinetics of sintering of the raw material, sublimation of ammonium hexafluorosilicate, and formation of
aluminum fluoride and alumina were described. The rate constants and activation energies of the reactions were
Today alumina is mainly produced from high-quality
low-silica bauxites by the widely used Bayer method.
The resources of high-quality bauxites in the Russian
Federation are limited, and the demand of the Russia’s
aluminum industry for alumina is met by domestic
resources to only 40–45% . At the same time, in Russia
there are inexhaustible resources of various non-bauxite
ores: kaolin rocks, high-alumina shales, anorthosites,
alkaline aluminosilicates, etc. . Much promise is shown
by kaolin and kyanite concentrates whose alumina content
reaches 62.6%, and in this respect they are comparable
with high-quality bauxites.
The goal of this study was to examine ﬂ uoride proces-
sing of non-bauxite ores and develop an alumina recovery
procedure that would be comparable in proﬁ tability with
the alumina recovery from high-quality bauxites. In so
doing, we performed integrated processing of non-bauxite
ores with the preparation of ammonium hexaﬂ uorosilicate,
aluminum ﬂ uoride, and other valuable products.
As starting non-bauxite ore we used kaolin concentrates
of KN-73 (50.28, Al
O 0.14, K
O 1.20, calcination loss 12.86%) and KM-1
O 1.33, calcination loss 12.83%) grades (Chalgan
deposit of kaolin-containing sands, Amur oblast). The
alumina content of the dehydrated kaolin concentrates
reaches 39.09 and 42.60%, respectively, but the cost of
recovery of these concentrates from kaolin-containing
sands is considerably lower than the cost of production
of kyanite concentrates from high-alumina shales and
gneisses with a massive texture.
As ﬂ uorinating agent we used ammonium hydrogen
diﬂ uoride (NH
) of analytically pure grade, produced
by Galogen Joint-Stock Company (Perm). Under normal
is a relatively inert crystalline
powder which is considerably safer environmentally
than ﬂ uorine and hydroﬂ uoric acid. However, at elevated
temperatures it becomes a powerful ﬂ uorinating agent.
The melting point of ammonium hydrogen diﬂ uoride is
126.8, and the decomposition point, 238°С.
The starting components taken in stochiometric ratios
were thoroughly ground and placed in Teﬂ on, glassy
carbon, or platinum cups or crucibles. The sample weight
was 5–40 g. Experiments were performed in a nickel or
nickel-lined steel reactor. The initial charges were heated
at 50–550°C for 0.25–4.5 h, with condensation of volatile
products. The volatile products were collected with a two-
zone condenser. Argon was used as carrier gas.
The initial samples, intermediate phases, and ﬁ nal
products were studied by X-ray phase analysis (DRON-
radiation), emission spectrum analysis (STE-1
spectrograph), and chemical methods. The content of
ammonia and ﬂ uorine in volatile products was determined
by titration of the resulting aqueous solutions with
sulfuric acid and thorium nitrate, respectively. Thermal