ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 6, pp. 965!969. + Pleiades Publishing, Ltd., 2008.
Original Russian Text + L.I. Bel
chinskaya, K.A. Kozlov, A.V. Bondarenko, G.A. Petukhova, M.L. Gubkina, 2008, published in Zhurnal Prikladnoi
Khimii, 2008, Vol. 81, No. 6, pp. 926!930.
OF SYSTEMS AND PROCESSES
Effect of Salt Modification on Adsorption Properties
of Acid-Activated Montmorillonite and Kaolinite
L. I. Bel
chinskaya, K. A. Kozlov, A. V. Bondarenko, G. A. Petukhova, and M. L. Gubkina
Voronezh State Forestry Academy, Voronezh, Russia
Lipetsk State Technical University, Lipetsk, Russia
Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia
Received July 9, 2007
Abstract-Effect of modification of a layered aluminosilicate, montmorillonite, and rigid-structure
kaolinite activated by sulfuric acid with solutions of magnesium chloride was studied in order to obtain
sorbents for wastewater treatment to remove organic compounds.
Because of the wide use of adsorption technol-
ogies in the present-day development and moderni-
zation of various industries, it becomes an increas-
ingly urgent task to create inexpensive and readily
available sorbents. A problem that remains topical
for extending the application range of sorption
materials is the possibility of purposefully control-
ling the chemical structure of their surface layer
and thereby of widely varying the adsorption-struc-
tural characteristics of adsorbents and improving
their selectivity and multifunctionality.
The set of physicochemical properties of natural
mineral sorbents is improved by their activation
and modification. By the activation is commonly
understood  the improvement of the sorption
activity under any treatment of a material, and by
modification, changes in the properties of sorbents,
with their original structure preserved. In the pres-
ent study, the adsorption properties of minerals
were improved by activating samples with 20% sul-
furic acid and modifying the activated samples with
a magnesium chloride solution.
As objects of study served two samples of natu-
ral silicates from a deposit in Lipetsk oblast, in
which the rock-forming minerals are montmoril-
lonite and kaolinite. Montmorillonite is a lay-
ered silicate material with an expanding structural
unit. In montmorillonite, silicon in the tetrahedral
layer is substituted by aluminum, and aluminum
in octahedral positions is partly substituted by
magnesium . As a result, there appears charge
deficiency compensated by interlayer ions having
an exchange capacity. In natural montmorillo-
nites, these are, as a rule, Na and Ca. The general
crystallochemical formula of montmorillonite is
] . nH
O [3, 4].
The montmorillonite clay used in the study con-
tained 65 wt % rock-forming mineral, with halloy-
site (20 wt %) and vermiculite (15 wt %) the rest.
Kaolinite is composed of two-layered packets:
one silica-oxygen tetrahedral layer of composition
and one aluminum3oxygen3hydroxyl oc-
tahedral layer of composition [Al
layers are combined into a packet by a hydrogen
bond formed by oxygen ions of the silicon3oxygen
layer and OH groups of the octahedral layer [3, 4].
The structural unit is [rigid,] incapable of swelling.
The composition of the sample under study was as
follows (wt %): kaolinite 75, silicite 10, illite 5, and
goethite 10 (with a trace amount of montmorillonite).
The acid treatment of the natural samples was
performed by the following scheme: montmorillon-
ite (kaolinite) with a grain size less than 0.5 mm was
dried at a temperature of 130oC for 2 h. The dried
material was mixed with 2.33 M sulfuric acid in
a mass ratio of 1: 3 and activated under permanent
agitation and heating on a water bath. The result-
ing slurry was filtered with a vacuum pump through
a filter made of synthetic fibers. The filter cake
was washed with distilled water to pH 4 and dried