ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 3, pp. 370 !374. + Pleiades Publishing, Ltd., 2008.
Original Russian Text + L.E. Derlyukova, M.V. Vinokurova, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 3, pp. 384 !388.
AND INDUSTRIAL INORGANIC CHEMISTRY
Effect of SO
on Chlorination of Zinc Ferrite ZnFe
and a Mixture of ZnO and Fe
L. E. Derlyukova and M. V. Vinokurova
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka,
Moscow oblast, Russia
Received July 21, 2007
Abstract-Results of thermodynamic calculations and kinetic studies of the reaction of zinc ferrite ZnFe
and of a mixture of oxides, ZnO and Fe
, with chlorine and SO
Chloride sublimation processes are widely used to
produce anhydrous chlorides and oxychlorides in in-
organic synthesis, recover rare and nonferrous metals
from complex polymetallic raw materials in metal-
lurgy, purify compounds to remove impurities, and
separate metals . In all these cases, the reacting
systems are multicomponent.
Introduction of a new reagent into a heterogeneous
system is, as a rule, accompanied by a change not
only in the equilibrium composition of the products
formed, but also in the rates of particular reactions
occurring in the system . It has been shown previ-
ously that results obtained in chlorination of individ-
ual metal oxides cannot be used to make definite
conclusions about the chlorination kinetics of their
mixtures [5, 6]. A noticeable influence on the rate of
chloride sublimation is exerted by the composition of
the gas phase. For example, addition of sulfur dioxide
to chlorine accelerates the process even in those cases
when the sulfur oxide does not react with a metal
oxide in the absence of chlorine . It has been found
that the recovery of tungsten dioxydichloride from
scheelite3wolframite concentrates into the sublimate
increases in the presence of sulfur dioxide .
To find the optimal conditions of selective re-
covery of metals in the form of chlorides, it is highly
important to study the reaction of double oxides or
their mixtures with chlorine and the effect of the com-
position of the gas phase on this process.
However, published data on the behavior of double
oxides in the atmosphere of chlorine are scarce. It was
found in  that, in the reaction of cobalt and
nickel ferrites with chlorine, the degree of chlorination
of the elements contained in these compounds differs
from that observed in chlorination of their individual
oxides, but this fact was not explained.
Most kinds of zinc raw materials contain a large
amount of iron. The basic form of zinc compounds in
oxidized materials is ferrite. It has been found in
a study of the reaction of ZnO with mixtures of chlor-
ine and sulfur dioxide that formation of a stable zinc
sulfate markedly diminishes the rate at which zinc
chloride is formed . By contrast, formation of iron
sulfate in the reaction of Fe
with chlorine in
the presence of SO
leads to an increase in the degree
of chloride sublimation of iron .
Here we report the results of thermodynamic calcu-
lations and kinetic studies of chlorination of zinc
and of an equimolar mixture of ZnO
in the presence of SO
The equilibrium compositions of the gas and con-
densed phases of the system under study were calcu-
lated by the method of free energy minimization by
ASTRA software  in the temperature range 3003
800oC. The chlorination kinetics was studied at 5003
700oC by the gravimetric method under isothermal
conditions on an installation that automatically re-
corded the variation of mass with time. The sensitivity
of the installation was 0.001 g per 1 mm of the scale.
The weighed portion of a sample was 0.1803 0.200 g.
Under the experimental conditions, the Cl
was 1 : 1. The total gas flow rate was 200 ml min
at a linear flow velocity of 0.05 m s
. Such a rate of
gas supply to the surface did not impose any limita-
tions on the chlorination process.