Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 3, pp. 332338.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © V.Yu. Prokof’ev, N.E. Gordina, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 3, pp. 360366.
AND INDUSTRIAL INORGANIC CHEMISTRY
A Study of Thermal Treatment and Hydrothermal Crystallization
Stages in Production of Granulated NaA Zeolite
from Mechanically Activated Metakaolin
V. Yu. Prokof’ev and N. E. Gordina
Research Institute for Thermodynamics and Kinetics of Chemical Processes, Ivanovo State University of Chemistry
and Technology, Ivanovo, Russia
Received January 11, 2013
Abstract—NaA zeolite was synthesized from mechanically activated granulated mixtures of metakaolin, sodium
hydroxide, and aluminum oxide. The thermal treatment and hydrothermal crystallization processes were studied. It
is shown that the optimal temperature of thermal treatment of grains based on a mechanically activated metakaolin
is 600°C at a NaA zeolite content of about 65 wt %. Raising the calcination temperature leads to a decrease in the
content of the zeolite and to formation of nepheline. It was found that the optimal concentration of the crystal-
lization solution of NaOH is 2–4 M. Under these conditions, the content of the zeolite exceeds 90 wt %. Raising
the alkali concentration leads to a decrease in the content of the zeolite and to its recrystallization into sodalite.
The industry widely employs synthesis of granulated
NaA zeolite from kaolin raw materials in which,
similarly to the zeolite, the Si : Al ratio is close to 1 : 1.
Kaolin is dehydrated until metakaolin is obtained, and
the latter is subjected to hydrothermal crystallization in
a solution of sodium hydroxide and aluminate [1–3].
Syntheses of this kind are performed in multiple stages,
with a prolonged exposure in each crystallization stage
and formation of a large amount of wastewater.
A promising way to improve the efﬁ ciency of
heterophase syntheses is by using mechanochemistry
to activate the solid phase [4, 5]. Mechanical treatment
of the solid phase in activating mills makes it possible
to perform the subsequent stages in milder conditions,
reduce (and, occasionally, fully eliminate) the amount
of the liquid phase, and obtain nanosize particle of the
Previously, a mechanochemical synthesis of NaA
zeolite from metakaolin and solid sodium hydroxide
has been suggested [6–8]. It was noted that a successful
mechanochemical synthesis is only possible with an
excess of Al
relative to the stoichiometry of the
zeolite synthesis reaction. It has also been shown 
that the optimal time of of fusion mixture treatment in a
mill is determined by synthesis of cubic and tetragonal
sodium aluminates. After a mechanical activation in a
vibration mill and a thermal treatment, the content of
NaA zeolite phase did not exceed 60 wt %. To raise
the crystallinity of the target product, it is necessary to
perform the hydrothermal crystallization in an alkaline
solution [7, 8].
Studies of the fundamental physicochemical aspects
of the zeolite synthesis have shown that this process is
kinetically reversible, and the ﬁ nal product is determined
not so much by the thermodynamic parameters of the
system as by the process conditions.
Thus, our study reported here proceeds with
those commenced previously [6–8] and is concerned
with analysis and optimization of stages of thermal
treatment and hydrothermal crystallization of grains
from mechanically activated mixtures of metakaolin
and sodium hydroxide, intended for synthesis of NaA