ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 2, pp. 175!180. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + D.V. Makarov, A.T. Belyaevskii, Yu.P. Men’shikov, D.P. Nesterov, M.F. Yusupova, 2007, published in Zhurnal Prikladnoi
Khimii, 2007, Vol. 80, No. 2, pp. 177!182.
AND INDUSTRIAL INORGANIC CHEMISTRY
A Study of the Mechanism and Kinetics of Interaction
between Nepheline Powder and Ammonium Hydrofluoride
D. V. Makarov, A. T. Belyaevskii, Yu. P. Men’shikov,
D. P. Nesterov, and M. F. Yusupova
Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Resources,
Kola Scientific Center, Russian Academy of Sciences, Apatity, Murmansk oblast, Russia
Received September 4, 2006
Abstract-Behavior of a skeleton silicate, nepheline, in the reaction of fluorination with ammonium hydro-
fluoride was studied by means of differential-thermal, X-ray phase, and chemical analyses, IR spectroscopy,
and scanning electron microscopy.
As shown by numerous studies , use of fluo-
ride metallurgy may favor a more intensive develop-
ment of a closed technology for processing of mineral
raw materials and a transition to conditioning of waste
or its components into products compatible with
ecologically safe technologies.
However, practical development of hydrofluoride
methods for processing of various ores and concen-
trates requires more detailed and specific evidence
about mechanisms and kinetics of interaction of both
ores and rock-forming minerals with NH
. It has
been found, in particular, that many ore minerals are
fluorinated under more severe conditions, compared
with silicates [1, 7]. This offers an opportunity to
perform desilicification of concentrates, e.g., at lower
temperatures (below the melting point of ammonium
hydrofluoride), without evolution of NH
the gas phase in the first stage.
It was shown in  that decomposition of island
silicates is the most difficult process. Complete fluo-
rination of such minerals with NH
in Teflon autoclaves at 200oC. At the same time, it
has been found  that the structure of magnesium
silicates has no noticeable effect on the fluorination
It is, therefore, of indubitable interest to study
specific features of interaction between a set of silicate
minerals of varied structure with ammonium hydro-
In this study, the behavior of powdered nepheline
in the reaction of fluorination was examined. Nephe-
line (simplified formula Na
) is a mineral
with aluminosilicate tetrahedra (skeleton silicate),
which belongs to the hexagonal crystal system.
The structure of minerals that belong to the nepheline
group is based on a tetrahedral skeleton of the type of
high-temperature tridymite, in which half of Si atoms
are substituted by Al and lattice voids are filled with
alkali metal cations neutralizing the negative charge
of the skeleton .
A nepheline concentrate containing (wt %): SiO
29.48, and Na
O 13.28, and the mono-
mineral fraction of nepheline from a rock sample from
the Khibiny massif were used in the study. As the
fluorinating agent served twice recrystallized ammoni-
um hydrofluoride NH
of analytically pure grade.
The thermogravimetric analysis was carried out on
a Q-1500D derivatograph (Hungary) in air in the dy-
namic and quasi-isothermal modes. The X-ray phase
analysis (XPA) of the reaction products was made on
a DRON-2 diffractometer with Cu
radiation. The IR
spectral study was performed on a UR-20 instrument.
The surface of particles of nepheline powder and
reaction products was analyzed by means of digital
scanning electron microscopy (SEM) on a computer-
ized LEO-420 electron microscope (Germany) .
To study the degree of decomposition of the min-
eral after leaching, the solid residue was spectro-