1070-4272/03/7609-1423$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 9, 2003, pp. 1423!1426. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 9,
2003, pp. 1463!1466.
Original Russian Text Copyright + 2003 by Sych, Kartel’, Kovtun.
AND ION-EXCHANGE PROCESSES
Preparation and Characteristics of a Cation Exchanger
Based on Oxidized Anthracite
N. V. Sych, N. T. Kartel’, and M. F. Kovtun
Institute of Sorption and Endoecological Problems, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received October 28, 2002; in final form, July 2003
Abstract-The features of anthracite oxidation as influenced by temperature and time were determined.
Physicochemical and sorption characteristics of the resulting cation exchanger were studied.
Many sorts of natural coals, similar to activated
coals, exhibit cation-exchange characteristics, which
can be enhanced by oxidative and thermal treatment
. Oxidation of ordinary activated coals at heating
to 4003450oC in air yields so-called oxidized coals
[1, 5] having a pronounced capability for selective ion
exchange owing to the presence of surface acidic
groups substituting metal cations for hydrogen ions.
They are also capable to form surface complexes with
metal ions and are catalytically active in some reac-
tions. These characteristics can be efficiently used for
thorough purification of process solutions, selective
recovery and concentration of impurities , and
production of high-purity substances.
It was of interest to study the possibility of produc-
tion of cation exchangers based on anthracite, cheap
natural coal with inexhaustible resources, high content
of carbon, and low ash content.
The goal of this work was to determine the opti-
mum temperature3time conditions of anthracite oxida-
tion and to study physicochemical and sorption char-
acteristics of the resulting cation exchanger.
Experiments were performed with anthracite of
the A type,
crushed to particles with the size of 0.53
Initially anthracite was activated with steam at
850oC to the burn-out of 20, 40, and 60%. The result-
ing samples were oxidized in humid air at 270, 320,
and 370oCto20330% burn-out. To estimate the effi-
ciency of oxidation of activated anthracite, the initial
(fossil) coal was also subjected to oxidation.
During oxidation, the burn-out was determined at
certain time intervals, and the static exchange capacity
(SEC) was determined.
Donetsk coal field (Sverdlovsk, Lugansk oblast).
In some cases, we measured pH values of oxidized
samples and the volume of sorption pores with respect
to benzene and methanol , studied the sorption
activity with respect to iodine and methylene blue
(MB), measured the specific surface area S
respect to argon, and analyzed oxygen-containing
groups by titration with bases of various strength
(Boehm method) . According to this method, the
total content of oxygen-containing carboxy and phen-
olic groups was determined from sorption of 0.1 N
NaOH solution, the content of weakly and strongly
acidic groups, from sorption of 0.1 N Na
tion, and the content of strongly acidic carboxy
groups, from sorption of 0.1 N NaHCO
content of phenolic and weakly acidic carboxy groups
was determined from the corresponding difference in
the SEC values.
It is well known  that the exchange capacity of a
carbon cation exchanger is affected by the chemical
nature of the raw material, its porosity, and specific
surface area, i.e., by factors governing the accessibil-
ity of reaction centers at which ionogenic groups
are formed. Coals and, in particular, anthracite are
peculiar natural compounds with undeveloped poros-
ity. The specific surface area of fossil anthracite is
small (0.731.0 m
); therefore, it is preactivated to
develop the porous system and uncover new active
centers accessible for atmospheric oxygen. In turn,
owing to formation of various acidic groups contain-
ing coordination-unsaturated oxygen atoms and
bonded to the system of conjugated bonds at the sur-
face of oxidized carbons, the subsequent reactions of
carbons with some metal cations involve not only
exchange of hydrogen ions for cations but also forma-
tion of more or less stable surface complexes in which
functional groups of carbons serve as ligands.