1070-4272/01/7401-0028$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 1, 2001, pp. 28!30. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 1,
2001, pp. 29!31.
Original Russian Text Copyright + 2001 by Zonkhoeva.
AND ION-EXCHANGE PROCESSES
The Chemical Resistance of Chabazite from Transbaikal Region
E. L. Zonkhoeva
Geological Institute, Siberian Division, Russian Academy of Sciences, Ulan-Ude, Buryatia, Russia
Received March 3, 2000
Abstract-The chemical resistance of natural chabazite of Margintui volcanic field (Transbaikal Region)
in 0.01, 0.1, 1.0, and 3.0 N HCl at was studied in relation to the treatment time. The order, degree, and rela-
tive rate of cation extraction from the chabazite phase were determined.
Studying the chemical resistance of zeolites is im-
portant for understanding the mechanism of their crys-
tallization under natural and artificial conditions. Acid
treatment can be used for preparing zeolitic sorbents
and catalysts with controllable properties, which sig-
nificantly extends the possibilities of their application.
At treatment of zeolites with dilute acid solutions
the proton of the acid first interacts with the mole-
cules of zeolite water to form hydroxonium ions par-
ticipating in cation-exchange reactions . At higher
concentrations of the acid the proton interacts with
the oxygen of the aluminosilicate skeleton with forma-
tion of hydroxide groups. As a result, the Al3O3Si
bonds break and aluminum(III) passes into the solu-
tion. In this stage, decationization and dealuminization
A majority of works is devoted to chemical resist-
ance of zeolites, especially of mordenites. At the same
time, the resistance of chabazite is studied insuffi-
ciently. For example, dealumination and amorphiza-
tion of chabazite boiled in 0.12 M solution of HCl has
been reported in . In 2 M HCl solution the chaba-
zite crystal structure degrades completely. Chabazite
is unstable to the action of HCl vapor at 200oC .
The acid resistance of natural chabazite was studied
by Piguzova . It was found that up to 12317% alu-
minum(III) is extracted from chabazite on treatment
with 0.006 N HCl. As a result, the maximal pore
volume increases by a factor of approximately 3 com-
pared to the initial sample. In 3 N HCl solution, the
reaches 15, but the mineral struc-
ture remains unchanged.
Bogdanova and Belitskii  studied the resistance
of 25 zeolite samples, including chabazite samples, to
treatment for 1 h with 1 N HCl on a boiling water
bath. Among the four groups, chabazite is classed
with the third group of zeolites, weakly reactive with
respect to dissolution. Treatment of chabazite with the
concentrated acid resulted in the extraction of 97% of
aluminum and total removal of Ca(II), Mg(II), and
Ba(II) ions. After treatment, the residual chabazite
retained the shape of the crystals.
Thus, no data are available on the chemical resist-
ance of chabazite in relation to the treatment time.
In this work, the chemical resistance of chabazite
from the Margintui volcanic field (Transbaikal Re-
gion) of the composition Ca
O in acid solutions of various con-
centrations was studied as a function of the contact
time. The grain size of the mineral was 132 mm.
Weighed portions of chabazite were placed in 0.01,
0.1, 1.0, or 3.0 N HCl for 1, 3, and 24 h at the solid-
to-liquid ratio of 1 : 30. After separating the phases,
chabazite was studied by X-ray phase analysis
(DRON-2.0 diffractometer, CuK
radiation) and by
chemical analysis for Si, Al, K, Na, Ca, and Mg. The
Al and Si concentrations were determined on an
SF-46 spectrophotometer and the K, Na, Ca, and Mg
concentrations, on a Saturn atomic absorption spec-
trophotometer (table, Fig. 1).
The samples treated with 0.01, 0.1, 1.0, and 3 M
acid solutions are denoted as A, B, C, and D, respec-
tively. The figures 1, 3, and 24 denote the treatment
time (h). The degree of extraction of exchangeable
cations and aluminum(III) is recalculated on oxides
(Fig. 1). The rate v of passing of the ions into the
solution was determined from the formula m = vt, and
the relative rate per gram of zeolite, by the formula
a = v/M (h
), where m is the weight (g) of the cation
passed into the solution in time t (h), and M is the
weighed portion of chabazite (g) .
The X-ray diffraction patterns of the initial sample