SYNTHESIS OF MAGNESIUM SILICATE BY HEAT TREATMENT
755
The presence of water in the reaction space is of much
significance for the layered silicate structure formation,
as confirmed by the experiments both with heat treatment
of magnesium hydroxide–silica dispersions differing in
the compositions of the dispersion medium and with
mechanical treatment of the components.
of Joint Studies by Institutes of the Ural and Siberian
Divisions, Russian Academy of Sciences.
REFERENCES
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Heat treatment of a magnesium hydroxide disper-
sion with sol(I) under water excess conditions enables
complete formation of a layered silicate structure. This is
strongly favored by a loose, fractal structure of the silica
sol particles as comprised of SiO4 tetrahedral networks.
Assisted by water which acts as a transporting agent, the
hydrated magnesium ions evidently experience weaker
steric hindrance to incorporation into the tetrahedral
networks of silica from the liquid phase.
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As to the synthetic route with the use of sol(II), the
reaction does not occur to the full extent. Considering
the identical physical conditions of syntheses and the
difference in the compositions of the dispersion media
for sols(I) and (II), this finding may be associated with
the specific composition of the dispersion medium in the
case of sol(II), which is essentially an aqueous alcoholic
solution.Apoorer solubility of magnesium hydroxide and
a lower mobility of magnesium ions in this medium [16]
affect the performance of water as an agent transporting
the magnesium ions into the structural units of silica.
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CONCLUSIONS
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(1) Synthesis of a layered silicate in all the examined
systems proceeds with participation of water which acts
as an agent transporting the magnesium ions into the
structural units of silica.
13. Handbook of Preparative Inorganic Chemistry: Guide to
Inorganic Chemistry, Brauer, G., Ed., New York: Aca-
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(2) Another factor that favorably affects the layered
silicate structure formation is the density (looseness) of
the microstructure of the silica particles, which limits the
penetration of the hydrated magnesium ions into the SiO4
tetrahedral networks of silica.
14. Tarasevich, Yu.I., Stroenie i khimiya poverkhnosti sloistykh
silikatov (Structure and Chemistry of the Layered Silicate
Surface), Kiev: Naukova Dumka, 1988.
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ACKNOWLEDGMENTS
16. Rabinovich, V.A. and Khavin, Z.Ya., Krartkii khimicheskii
spravochnik (Concise Chemical Handbook), 4 ed., St.
Petersburg: Khimiya, 1994.
This study was financially supported by the Program
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 5 2011