1070-4272/01/7409-1453$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 9, 2001, pp. 1453!1457. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 9,
2001, pp. 1413!1416.
Original Russian Text Copyright + 2001 by Bagreev, Broshnik, Strelko, Tarasenko.
AND ION-EXCHANGE PROCESSES
Effect of Oxidizing Treatment of Walnut Shell
on the Properties of Activated Carbon
A. A. Bagreev, A. P. Broshnik, V. V. Strelko, and Yu. A. Tarasenko
Institute of Sorption and Endoecological Problems, National Academy of Sciences
of Ukraine, Kiev, Ukraine
Received July 5, 1999; in final form, December 2000
Abstract-The effect of oxidizing treatment of walnut shell on the yield of activated carbon and on its pore
structure was studied.
We have shown recently that active carbons (AC)
with acceptable structural and sorption characteristics
can be obtained by a traditional procedure (carboniza-
tion with subsequent activation) from walnut shell
(WS) with the yield of about 10%. At the same time,
it is known that fruit kernels and various nut shells are
cellulose materials , and the procedures conven-
tionally used in their heat treatment can be extended
to the technology of obtaining AC .
Preliminary oxidation is one of the methods for the
treatment of cellulose materials with the aim to im-
prove the pore structure and increase the yield of
AC obtained from them [. In this case we must dis-
tinguish between the action of oxygen as an external
agent, the excess of which will result in complete
combustion of a polymer, and the action of oxygen
incorporated into elementary units of a polymer and
taking part in the material cross-linking on heat treat-
ment. In the latter case oxygen promotes formation of
intermediate bridges and intra- and intermolecular
cross-links determining the formation of the molecular
structure of a carbon material.
Within limited temperature and concentration
ranges atmospheric oxygen also can play the same
role, but its excess is undesirable, since it decreases
the carbon yield at the expense of incontrolled de-
gradation of the polymer and ultimately results in a
loss of the AC quality. In view of the aforesaid the
method of [sparing] oxidizing heat treatment found
use in obtaining carbon fibers  and also synthetic
AC (SKN and SKS) .
In this work we studied the effect of preliminary
oxidizing treatment on preparation and properties
of AC based on WS.
The installation and procedures for oxidizing treat-
ment of WS, the carbonization of the oxidized materi-
al, and the activation of the resulting carbonizates
were described earlier . WS was preoxidized in
air at 1503330oC for 1310 h and carbonized in
flowing argon at a heating rate of 5 deg min
samples were kept at 800oC for 1 h. To obtain AC
with various degrees of combustion loss, the activa-
tion was carried out in steam under a pressure of
0.1 MPa at 750oC for 0.132h.
In this work after each stage of heat treatment we
measured changes in the weight X
(%) and volume
(%) of the samples under study (weight and
volume combustion loss), the pore volume with re-
spect to benzene V
), and also the yield
of AC R (%). The parameters of the pore structure of
the samples in various stages of the thermolysis: the
micropore volume V
), the sorption pore
), and the specific surface area
), were determined from the isotherms of
carbon dioxide adsorption at 0oC and of nitrogen ad-
sorption at 3196oC. The isotherms were treated by
generally accepted procedures of the modern adsorp-
tion theory [9, 10].
Structural changes resulting from the heat treatment
of the products were studied by X-ray diffraction (a
DRON-2 diffractometer), and the interplanar spacings
(A) were calculated. The static exchange capacity
) of the materials based on WS was
determined by alkali titration. In this work averaged
data of 335 experiments are given.
Oxidation of WS was accompanied by weight loss
and contraction of the material. Figure 1 gives the