ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 8, pp. 1220!1224. + Pleiades Publishing, Inc., 2006.
Original Russian Text + E.P. Lokshin, T.A. Sedneva, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 8, pp. 1238!1241.
AND INDUSTRIAL INORGANIC CHEMISTRY
On Stabilization of Anatase with the Fluoride Ion
E. P. Lokshin and T. A. Sedneva
Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Resources, Kola Scientific Center,
Russian Academy of Sciences, Apatity, Murmansk oblast, Russia
Received December 23, 2005; in final form, March 2006
Abstract-Introduction of fluoride ions into titanium oxo hydroxide causes calcination to result in the anatase
modification of titanium dioxide, which is stable up to temperature of no less than 900oC and retains a high
specific free surface area on heating.
For destruction of organic contaminants present in
aqueous solutions, methods for their photocatalytic
decomposition with anatase nanoparticles as a photo-
catalyst are being intensively studied . These
processes are especially promising for purification of
wastewater containing nonbiodecomposable contam-
inants . Methods based on hydrolysis of organo-
metallic titanium compounds have been for the most
part developed for synthesis of anatase nanopowders
Moreover, a highly dispersed anatase retaining
a high specific surface area on heating to a tempera-
ture of no less than 500oC is required as catalyst and
catalyst support for a number of processes of organic
synthesis . The thermal stability is necessary for
regeneration of the catalyst by high-temperature burn-
ing-out of tarry products accumulated in the catalyst
in the course of its operation .
It has been suggested to obtain materials of this
kind by hydrolysis of organic compounds of titanium
(ethylate, propylate, butylate, and methyl cellosolvate)
in the presence of stabilizers (hydrochloric or nitric
acid) with subsequent drying at 120oC to constant mass
and calcination at 500oC (calcination time not report-
ed). In some cases (not specified in the study), sam-
ples with a specific surface area of up to 105 m
have been obtained .
Titanium alkoxides are expensive and chemically
active, which requires that special intricate equip-
ment should be developed to enable their use in large-
scale production. In addition, the formation of Ti
upon calcination of a xerogel has been revealed by
EPR . Therefore, it was of interest to obtain ther-
mally stable anatase nanopowders from inorganic
precursors. The most interesting among them are
sulfate, chloride, and nitrate compounds of titanium,
which can be obtained by various methods from
mineral raw materials.
Titanium dioxide nanopowders obtained by plasmo-
chemical synthesis initiated by a pulsed electron beam
are a mixture of anatase and rutile. Their ratio in
a mixture could be controlled by varying the synthesis
Data on the structure of phases formed in hydrol-
ysis of sulfate, chloride, and nitrate solutions of ti-
tanium are contradictory . It has been shown,
however, that the crystal structure of the phases
formed and its subsequent change upon heating de-
pend on the composition of a starting titanium com-
pound and of the impurities contained in solution.
Metatitanic acid produced by thermal hydrolysis from
sulfuric acid solutions contains about 7 wt % SO
Its heating to about 850oC gives anatase, which is
transformed into rutile only at 8503950oC . At
higher calcination temperatures, micrometer-size pow-
ders of titanium dioxide are formed.
Metatitanic acid produced by thermal hydrolysis
from nitrate or chloride solutions is transformed into
rutile below 500oC .
The phase composition and coarseness of titanium
dioxide particles depend on the temperature (1503
250oC interval was studied) and time (10 min36h)of
the hydrothermal treatment . Nanocrystalline ana-
tase powders (crystallite size 10330 nm) were obtain-
ed by hydrothermal treatment of the sulfate TiOSO