ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 11, pp. 1761!1764. + Pleiades Publishing, Inc., 2006.
Original Russian Text + V.N. Lebedev, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 11, pp. 1781!1784.
AND INDUSTRIAL INORGANIC CHEMISTRY
Sulfate-Containing Zirconium Dioxide Powders Made
of Products of Baddeleyite Processing
V. N. Lebedev
Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials,
Kola Scientific Center, Russian Academy of Sciences, Apatity, Murmansk oblast, Russia
Received March 16, 2006
Abstract-Manufacture of sulfate-containing zirconium dioxide powders from basic zirconium sulfate, zir-
conium disulfate, and ammonium sulfatozirconate, which are sulfate-containing products of processing of
baddeleyite concentrate, was studied.
Zirconium dioxide nanopowders are used for
manufacturing specialty ceramics, catalysts, sorbents,
and other materials with special properties. Such
materials are commonly obtained from zirconium
oxychloride or oxynitrate, with composition and prop-
erties of the products obtained dependent on both
the starting salts and the method of powder prepara-
tion. Different crystalline modifications can be formed
even in the stage of precipitation at prolonged boiling
of hydrolysis precipitates or in an autoclave [1, 2].
The metastable cubic and tetragonal phases of zirco-
nium dioxide are formed by the thermal dehydration
below 3803 400oC and transform into the stable
monoclinic phase at higher temperature . The tem-
perature of the phase transitions and the properties of
powders depend on the preparation conditions and on
the presence of stabilizing impurities such as water,
cationic, and anionic impurities [43 6].
In catalysis, ZrO
modified with sulfate groups
came into use relatively recently. The modified ZrO
exhibits superacid properties, and its high specific sur-
face area (of the order of 100 m
) is retained on
heating . Therefore, we consider in this study
the manufacture of powders in which the content of
ions can be controlled by the starting materials.
As starting materials were used products of processing
of baddeleyite concentrate, i.e., basic zirconium sul-
fate (BZS), zirconium disulfate (ZDS), and ammoni-
um sulfatozirconate (ASZ) [10, 11]. ZrO
from zirconium oxychloride (ZOC) was used for
comparison. The above products were separated by
breakdown of baddeleyite concentrate with sulfuric
acid or by sintering with calcium carbonate. The con-
tent of the impurities in BZS and ZOC was about
wt %, and that in ZDS and ASZ,
1 0 10
31 0 10
wt %. The basic zirconium sulfate
was precipitated at the SO
molar ratios (m.r.)
of 0.8, 0.6, and 0.45.
Zirconium oxides were prepared by heating hy-
droxides or sulfate-containing products at 3803800oC.
The hydroxides were washed to remove sulfate ions to
various extents, or the sulfate-containing products
were heated without washing. According to data of
the thermal analysis, the sulfates decompose in the
range 6003800oC . Zirconium hydroxides were
prepared by back precipitation. To do this, a sample
of zirconium-containing precipitate was introduced
into a calculated amount of a 5% ammonia solution.
The zirconium hydroxide precipitate thus obtained are
pseudocrystalline and easy to filter . The pulp was
stirred for 2 h at pH 9, stored for 24 h to remove the
possible products of incomplete hydrolysis, and
washed to remove sulfate ions. The hydroxides were
dried at 120oC for 12 h. Then, they were treated in a
0.131.0 M H
solution for 12 h to be saturated
with sulfate groups.
The products obtained were subjected to X-ray
phase analysis (DRON-1 diffractometer, CuK
tion). The specific surface area was calculated from
the isotherms of low-temperature adsorption of ni-
trogen (BET). The content of the sulfate ions (count-
ing on SO
) in the samples was determined by X-ray
fluorescence analysis (FRA-1 analyzer).
The monitored parameters of the samples heat-
treated for 3 h are listed in Table 1.
Table 1 shows that the sintering of all samples,
except for ASZ, yields zirconium dioxide powders