Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 6, pp. 892−897.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.A. Lamberov, E.Yu. Sitnikova, A.Sh. Abdulganeeva, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 6, pp. 910−915.
OF SYSTEMS AND PROCESSES
Kinetic Features of Phase Transformation of Kaolinite
into Metakaolinite for Kaolin Clays
from Different Deposits
A. A. Lamberov, E. Yu. Sitnikova, and A. Sh. Abdulganeeva
Kazan (Volga Region) Federal University, Kazan, Tatarstan, Russia
Received July 7, 2012
Abstract—The rate of the endothermic process of kaolinite transformation into metakaolinite was examined by
X-ray phase and thermogravimetric analyses, as well as by means of differential scanning calorimetry, in relation to
the particle size distribution and crystal structure characteristics of kaolinite in kaolin clays from different deposits.
Natural kaolin clays are widely used today as feed-
stock in a well-known industrial method of preparation
of A-type zeolites [1, 2]. One of the major stages deter-
mining the sorption properties of the resulting product
consists in heat treatment of the clay raw material, which
induces transformation of the main rock-forming mineral
of kaolin clays, kaolinite, into a more reactive phase,
metakaolinite [2, 3] which forms, under appropriate
conditions, A-type zeolite. The conditions enabling this
phase transformation and the amount of the resulting
metakaolinite depend on the kaolinite content in the clay
raw material, as well as on the degree of crystallinity and
particle size distribution of kaolinite [4–8].
The sole criterion for choosing a clay for zeolite prepa-
ration is typically the kaolinite content therein, while all
of the above-mentioned parameters are to be taken into
account in order that a product with signiﬁ cant sorption
capacity could be obtained.
Here, we examined the rate of phase transformation of
kaolinite into metakaolinite in relation to the mineralogi-
cal composition of kaolin clays, as well as to the particle
size and crystal structure characteristics of kaolinite.
In our study we used clays from the following de-
posits: sample no. 1, from Kyshtymskoe deposit (Bash-
kortostan), sample no. 2, from Prosyanskoe deposit
(Ukraine), sample no. 3, from Druzhkovskoe deposit
(Ukraine), and sample no. 4, from Troshkovskoe deposit
This speciﬁ c choice was dictated by the facts that the
main mineral in the composition of these clay samples is
kaolinite (Table 1), and the molar ratio of silica to alumina
is close to that in A-type zeolite (Table 2) .
The elemental composition of the clay samples was
determined by the induced plasma emission spectrometry
on an OPTIMA 2000DV instrument.
The X-ray phase analysis of the clay samples was
carried out on a D8 ADVANCE (Bruker) diffractometer
radiation, graphite secondary beam monochroma-
tor).The qualitative phase composition was determined
by comparing the diffraction patterns recorded by us with
the reference patterns of the known kaolinite phases .
The degree of ordering of the crystal structure of kaolin-
ite was assessed using the Hinckley crystallinity index,
which integrated characteristic is a measure of the degree
of crystallinity perfection of kaolinite  as estimated
from the intensity of the d/n ~ 7.2 Å reﬂ ection: The higher
the intensity, the better crystallized the structure.
The derivatograms of the clay samples were recorded
on a NETZSCH STA 449C instrument at temperatures
within 30–1100°C in air atmosphere at a rate of 30 deg