1070-4272/03/7604-0663 $25.00 C 2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 4, 2003, pp. 663!665. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 4, 2003,
Original Russian Text Copyright + 2003 by Chirkst, Krasotkin, Cheremisina, Streletskaya, Ivanov.
Determination of the Surface Area of Minerals by Sorption
of Methylene Blue and Thermal Desorption of Argon
D. E. Chirkst, I. S. Krasotkin, O. V. Cheremisina, M. I. Streletskaya, and M. V. Ivanov
St. Petersburg State Mining Institute (Technical University), St. Petersburg, Russia
Received May 30, 2002
Abstract-The specific surface area of a number of natural aluminosilicates was determined by the methods
of thermal desorption of argon and limiting sorption of Methylene Blue. The correlation between the results
obtained using these two techniques was discussed.
In view of the undertaken studies of the sorption
properties of mineral components of soils, the spe-
cific surface area and exchange capacity of a number
of minerals were analyzed. It was necessary to con-
sider the correlation between the results obtained in
determining the specific surface area by the common-
ly accepted methods of thermal desorption of argon
 and limiting sorption of Methylene Blue (MB)
. Natural aluminosilicates commonly occurring
in northwestern Russia: kaolinite Al
Cambrian blue clay K
], oligoclase (Na
], were chosen for the study.
Mineral samples were ground and sieved into frac-
tions with different particle sizes. The specific surface
area of the minerals was determined by gas chroma-
tography by the method of thermal desorption of ar-
gon  and from MB sorption from solution .
According to the latter technique, a 0.532-g portion
of air-dried mineral powder passed through a sieve
with 0.130.4-mm mesh was placed in a 100-cm
ical vessel. A 20350-ml portion of a 10
lution of MB was introduced with a pipette. Then
the contents of the vessel were shaken and the result-
ing suspension was allowed to stay for 12314 h.
The dyed suspension was twice filtered through
[blue ribbon] filter. First portions of the filtrate
(~10 ml) were discarded because of the sorption of MB
on the filter. Pipette was used to take 1-ml samples of
the filtrate and the initial MB solution. The aliquots
were diluted with water to 100 ml. An SF-46 spec-
trophotometer was used to measure the optical density
of an MB solution under study and of the initial MB
solution at a wavelength of 665 nm. The MB concen-
tration in the filtrate was calculated using the formula
The exchange capacity E was calculated (with ac-
curacy of 0.1 mg-equiv kg
) by the formula
E = 7777
DcV 0 10
where Dc is the difference of the concentrations of the
initial MB solution and that under study (equiv l
V is the amount of the initial solution (cm
), and m is
the mass of a mineral sample (g).
The exchange capacity of the minerals studied was
used to calculate the specific surface area. The land-
ing area of a single MB cation is 95.6 A
to X-ray diffraction analysis . If it is assumed that
the limiting sorbed amount of MB corresponds to
a monomolecular layer of the dye on faces of layered
minerals, then the specific surface of these minerals,
) can be calculated using the formula
where E is the exchange capacity of a mineral for MB
is the Avogadro number, and
is the area occupied by an MB cation.
The results of determinations are listed in the table.
As determination error is given the reproducibility of
the values obtained.
The measurement results suggest the following.
With the average particle diameter decreasing by