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Russian Journal of Applied Chemistry, Vol. 74, No. 3, 2001, pp. 400!403. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 3,
2001, pp. 393!396.
Original Russian Text Copyright + 2001 by Karetina, Shubaeva, Dikaya, Khvoshchev.
AND ION-EXCHANGE PROCESSES
Sorption of Lead(II) from Aqueous Solutions
by Synthetic Zeolites
I. V. Karetina, M. A. Shubaeva, L. F. Dikaya, and S. S. Khvoshchev
Grebenshchikov Institute of Silicate Chemisty, Russian Academy of Sciences, St. Petersburg, Russia
Corning Research Center, St. Petersburg, Russia
Received November 2, 1999; in final form, January 2000
Abstract-A comparative study of the sorption of lead(II) from dilute aqueous solutions by synthetic
faujasites, chabazites, mordenites, erionites, phillipsites, and type A zeolites was performed. The most promis-
ing sorbents are low-silica chabazites and potassium erionites with relatively high SiO
Recently, interest in the possibility of recovering
heavy-metal ions from natural water and wastewater
has been again aroused by the increasingly stringent
environmental regulations. The high selectivity of
zeolites with respect to lead ions has long been known
. For obvious reasons the preference has been
given to natural zeolites . At the same time,
there are no published comparative data for main types
of synthetic zeolites. This communication presents
some results obtained in studying the ion-exchange
capacity for lead(II) of synthetic faujasites, type A
zeolites, chabazites, erionites, mordenites, and phil-
lipsites treated with solutions with low concentration
ions in the presence of predominant amounts
All the zeolites studied were synthesized by the
technique described in .
The composition of
the crystals was determined by methods of chemical
analysis (Table 1).
The estimates of the ion-exchange capacity of some
zeolites for lead are presented in Table 2.
In the first case, weighed portions of zeolites (1.53
2.0 g) were treated with solutions containing lead(II)
in amounts equivalent to the content of cations in
crystals. In the second case, the solutions used for
treatment contained the same amount of lead(II) and
a 10-fold excess of calcium and magnesium ions.
Each zeolite was thrice treated with the solution for
6 days at room temperature with intermediate wash-
ings. In the process, up to 2 l of the solution was
used, depending on the required component ratios.
As seen from Table 2, Na
ions in zeolites are only
At the Corning Research Center.
in part replaced by Pb
ions even upon treatment
with purely lead solutions. Under the conditions of
competition with Mg
ions, the degree of
exchange for Pb
markedly decreases, but the selec-
tivity order CHA > FAU > LTA remains unchanged.
As seen from Table 2, the contents of PbO and CaO
are comparable, even though the Ca
in solutions is 10 times that of Pb
. At the same
time, only an insignificant part of Na
ions is replaced
under these conditions by Mg
The presence of Ca
ions has practically no effect,
either, on the possibility of lead(II) recovery from
solutions containing only 0.00006% Pb
with zeolites of different structural types exhibiting
similar behaviors. A similar conclusion was made in
 in reference to a number of natural zeolites. As
seen from Table 3, the NaFAU-2 faujasite with
ratio of 2.87 and low-silica chabazite
NaCHA-1 show the highest capacity for lead(II).
The main results obtained in studying the absorp-
tion of Pb
ions by zeolites are presented in Table 4.
Here, too, the solutions used contained 0.00006%
lead(II). The treatment was performed at room tem-
perature in the course of 15 days.
At so low degrees of exchange (the PbO/Al
ratio in the zeolite crystals subjected to treatment was
0.00130.004) it is difficult to speak of any clear rela-
tionship between the composition of zeolites and their
ability to absorb lead(II). However, some conclusions
can be made. Large cations are less firmly bound to
the zeolite lattice, and, with increasing size of alkali
metal cation in a zeolite, the ion-exchange sorption of
lead(II), as a rule, becomes stronger. This is observed
in going from Li
in the case of faujasites, and